The Kosterlitz-Thouless model in Perovskite superconductors

Il Nuovo Cimento D - The applicability of the Kosterlitz-Thouless theory to HTSC is examined. The model initially presented in its general lines for bidimensional systems is then applied to...     

Field excited phosphorescence in X-irradiated potassium halide crystals

Light emission is observed at room temperature from X-irradiated KC1, KBr and KI samples placed between insulated electrodes under high voltage excitation. The slow response of the effect to the electric field shows that metastable states are involved in the recombination process. The study of the brightness waves and the dependence of the light intensity on the temperature demonstrate that the excitation of the luminescence centers is obtained through a field assisted thermal ionization process.     

Electroluminescence in LiNbO3 single crystals

The light emission from LiNbO₃ single crystals caused by the applied a.c. high voltage is studied. It is interpreted as electroluminescence due to impact processes of field accelerated electrons. Two bands can be distinguished in the emission spectrum: one larger with the maximum at 660nm and one smaller at about 500nm.     

Recent developments of thermoluminescence studies in alkali halide crystals: Photostimulated thermoluminescence

Part I describes the processes inherent to thermoluminescence phenomena and discusses the information yielded by thermoluminescence measurements on a real crystal. A brief review of the results in alkali halides is presented.

In the second part, the method of photostimulated thermoluminescence is presented with a summary of the typical results obtained by the authors: a sample is previously X-rayed at a high temperature; next trap filling is obtained by illumination with monochromatic light; the sample is then heated and the glow curve recorded. The process bears some analogy to photoconductivity, with higher sensitivity; moreover it allows the separation of the electron from the hole contribution and evidences different mechanisms of trap filling.

In the last part a recent development of the method is shown, namely the study of photostimulated thermoluminescence in additively colored alkali halide crystals.     

High field electrical properties of CdF2 crystals doped with rare earth ions

The electrical properties of CdF₂ crystals doped with Eu³⁺ and Gd³⁺ are described. A reversible “forming” effect is observed under high electric fields. The effect seems to be connected with a reversible modification of the potential barrier at the metal-insulator contact.     

Electroluminescence in CdF2 crystals

Electroluminescence is observed in CdF₂: Eu and CdF₂: Gd single crystals at liquid nitrogen temperature. The comparison of the emission spectra with those obtained from the same materials under X-ray excitation shows that the electric field stimulates either the intrinsic luminescence amd that due to the doping substance. The dependence of the brightness on the temperature is also reported and compared with the intrinsic luminescence efficiency. The effect is used for measuring the rare earth luminescence decay times.     

Analysis of polar organic contaminants in surface water of the northern Adriatic Sea by solid-phase extraction followed by ultrahigh-pressure liquid chromatography–QTRAP® MS using a hybrid triple-quadrupole linear ion trap instrument

Water-soluble polar organic contaminants are discharged by rivers, cities, and ships into the oceans. Little is known on the fate, pollution effects, and thresholds of toxic chemical mixtures in the marine environment. A new trace analytical method was developed for the multi-compound analysis of polar organic chemical contaminants in marine waters. The method is based on automated solid-phase extraction (SPE) of one-liter water samples followed by ultrahigh-pressure liquid chromatography triple-quadrupole linear ion-trap mass spectrometry (UHPLC–QTRAP^® MS). Marine water samples from the open Adriatic Sea taken 16 km offshore from Venice (Italy) were analyzed. Method limits of quantification (LOQs) in the low picogram per liter (pg/l) concentration range were achieved. Among the 67 target chemicals analyzed, 45 substances could be detected above the LOQ. The chemicals detected at the highest concentrations were caffeine (up to 367 ng/l), nitrophenol (36 ng/l), 2,4-dinitrophenol (34 ng/l), 5-methyl-1H-benzotriazole (18.5 ng/l), sucralose (11 ng/l), 1H-benzotriazole (9.2 ng/l), terbuthylazine (9 ng/l), alachlor (7.7 ng/l), atrazine-desisopropyl (6.6 ng/l), diethyltoluamide (DEET) (5.0 ng/l), terbuthylazine-desethyl (4.3 ng/l), metolachlor (2.8 ng/l), perfluorooctanoic acid (PFOA) (2.5 ng/l), perfluoropentanoic acid (PFPeA) (2.3 ng/l), linuron (2.3 ng/l), perfluorohexanoic acid (PFHxA) (2.2 ng/l), diuron (2.0 ng/l), perfluorohexane sulfonate (PFHxS) (1.6 ng/l), simazine (1.6 ng/l), atrazine (1.5 ng/l), and perfluorooctane sulfonate (PFOS) (1.3 ng/l). Higher concentrations were detected during summer due to increased levels of tourist activity during this period.     

Electrical properties of CdF2 films

The electrical conduction at room temperature is examined in CdF₂ films between 200 and 2000 Å thick. The current response is studied, and two conductivity states alternating with a memory switching condition are obtained. The current is attributed, at least in part, to ionic transport.     

High field effects in insulating CdF2: Gd crystals

CdF₂ crystals doped with Gd, before any conversion to semiconductor, exhibit at low temperatures electrical current and electroluminescence with d.c. voltage applied.The electrical conduction, attributed to electrons, is bulk limited and the i = i (V, T) characteristics are interpreted as a Poole-Frenkel conduction.The electroluminescence, due to intrinsic and impurity emission, is attributed to the impact process of field accelerated electrons, which give rise to electron-hole pair formation and impurity centre excitation.