Fluorine determination in human and animal bones by particle-induced gamma-ray emission

Fluorine was determined in the iliac crest bones of patients and in ribs collected from post-mortem investigations by particle-induced gamma-ray emission based on the ¹⁹F(p,p′γ)¹⁹F reaction, using 2.0/2.5 MeV protons. The results indicate that for 68% of the human samples the F concentration is in the range 500–1999 μg g^–1. For comparison purposes fluorine was also determined in some animal bones; in some animal tissues lateral profiles of fluorine were measured.     

Photoluminescence and spectral holeburning in europium-doped MgS nanoparticles

Luminescence and power-gated spectral holeburning studies have been performed on Eu-doped MgS nanoparticles. These particles are atomically tailored to produce and control the relative concentration of Eu(2+) and Eu(3+), which is necessary for power-gated holeburning. The spectral holes are permanent at low temperatures. Optical studies show that the electron-phonon coupling is stronger in nanoparticles than in thin films or microparticles of the same material. This is the reason for inherently broader spectral holes in nanoparticles as compared to microparticle or thin-film samples. Temperature broadening of spectral holes in nanoparticles follows a T(2.4) behavior, a faster rate than thin films or microparticles. This behavior can be attributed to the glassy nature of the particles produced.     

Effects of mechanical and thermal stresses on electric degradation of polyolefins and related materials

Degradation under the simultaneous effects of mechanical stress and temperature in polyolefins (PE, PP), composites on their basis (PE+PP fibre, PP+PP fibre, PP+glass fibre) and radiation low-density polyethylene (X-LDPE) used in high-voltage cables obeys the thermofluctuation theory of Zhourkov (in certain σ and τ₀ intervals) based on the theory of Arrhenius is presented in the following form: τ_σ = τ₀ exp[(U₀ − γσ)/ RT] (1) where τ is durability. τ₀ is a constant (10⁻¹²-10⁻¹³s) equal to period of vibrations of atoms around equilibrium position, U₀ is the activation energy of the mechanical destruction process (at σ = 0), γ is a structure-sensitive parameter, T is absolute temperature and R is universal gas constant. Electric degradation under the effects of electric field and temperature in the materials mentioned above obeys the equation: τ_E = τ₀ exp[(W₀ − χE)/ RT] (2) Here, τ_E, W₀ and χ are analogous to τ_σ, U₀ and γ, respectively. It is assumed that the following equation is valid under the simultaneous effects of E, σ and T: τ_σ,E = τ₀ exp[(U₀ − (γσ + χE))/ RT]. (3) electric degradation