Preparation and characterization of new fluorotellurite glasses for photonics application

Glasses based on (85 − x)TeO₂-xZnF₂-12PbO-3Nb₂O₅ (x = 0-40) system have been studied for the first time for fabricating mid-infrared optical fiber lasers. The thermal and optical properties including UV-Vis, Raman as well as FTIR spectra are reported. It is demonstrated that increasing the ZnF₂ concentration to 30 mol% significantly increased the thermal stability of the glass. Adding ZnF₂ also reduced the hydroxyl (OH) content of the glass resulting in lower optical absorption in the mid-infrared region, which is crucial for infrared laser applications. The glass absorption cut-off edge near 400 nm blue-shifts with increasing ZnF₂ addition. Raman spectra show a depolymerization of the glass network with increasing transformation of TeO₃₊₁ to TeO₃ structures.     

Investigation of infrared emission and lifetime in Tm-doped 75TeO2:20ZnO:5Na2O (mol%) glasses: Effect of Ho and Yb co-doping

In this paper we describe fabrication and characterization of rare-earth-doped active tellurite glasses to be used as active laser media for fiber lasers emitting in the 2 μm region. The base composition is (mol%): 75TeO₂-20ZnO-5Na₂O with different concentrations of Tm³⁺, Yb³⁺ and Ho³⁺ as dopants or co-dopants. Optical properties of doped glasses were studied and pumping at 800 nm and at 980 nm were tested in order to compare the efficiency of two pumping mechanisms. Optical characterization carried out on glasses containing only Tm³⁺ ions indicated the optimum concentration of Tm₂O₃ in terms of emission efficiency as 1 wt%. The addition of 5 wt% of Yb₂O₃ to Tm³⁺-doped glasses led to the best results in terms of intensity of fluorescence emission and of lifetime values. Yb and Ho co-doped Tm-tellurite glass was measured in emission.     

Dynamics of the ionizing and magnetic fronts in the radialcompression stage of a DPF current sheath

Further results regarding the sudden drop of dense plasma focus (DPF) neutron yield at low pressure are presented. Experimental measurements of temporal evolution of magnetic piston MP (interface plasma-magnetic field) and current sheath ionizing front IF (interface plasma-neutral gas) are performed in the radial compression stage of DPF discharges. At the optimum deuterium pressure for neutron yield (1.5 mb), MP and IF have similar r(t) functions, so that the thickness of the sheath remains practically constant (~0.2 cm) in the whole stage. At the lower pressure limit for neutron yield (1 mb) the sheath begins the radial compression stage with a smaller thickness (~0.1 cm) and in the last 35 ns the IF moves forward (relatively to the MP) with a velocity of 7.5E+7 cm/s and the thickness in the layer reaches a value of ~0.5 cm. This sudden acceleration of the IF is interpreted as the main cause of the lower pressure limit in the neutron yield     

Synthesis and magnetic properties of ZnFe2O4 obtained by mechanochemically assisted low-temperature annealing of mixtures of Zn and Fe oxalates

The mechanism of formation of zinc ferrite (ZnFe₂O₄) from ZnC₂O₄·1.8H₂O-2Fe^IIC₂O₄·2H₂O and ZnC₂O₄·1.8H₂O-Fe₂^III(C₂O₄)₃·6H₂O mixtures is investigated. By combination of TG and XRPD measurements it has been shown that microcrystalline ZnFe₂O₄ forms from physical mixtures after prolonged annealing at 1000 °C while nanocrystalline ZnFe₂O₄ powders are produced by mild annealing (1 h at 500 °C in air) of mechanically activated mixtures. The magnetic properties of ZnFe₂O₄ powders obtained from physical and from milled mixtures are compared.     

Anions as Triggers in Controlled Release Protocols from Mesoporous Silica Nanoparticles Functionalized with Macrocyclic Copper(II) Complexes

Three different mesoporous silica nano‐sized materials ( SC1 , SC2 , and SC3 ), loaded with [Ru(bipy)₃]²⁺ dye (bipy=bipyridine) and functionalized on the external surface with three macrocyclic copper(II) complexes ( C1 , C2 , and C3 ), were synthesized and characterized. When SC1 , SC2 , and SC3 were suspended in water, the entrapped [Ru(bipy)₃]²⁺ dye was free to diffuse from the inner pores to the solution. However, addition of anions induced certain degrees of pore blockage, with subsequent dye release inhibition. Small monovalent and divalent anions were unable to induce complete pore blockage, whereas bulky and highly charged anions induced marked reductions in [Ru(bipy)₃]²⁺ delivery. The best [Ru(bipy)₃]²⁺ delivery inhibitors were ATP and hexametaphosphate anions. Inhibition was ascribed to the interaction of the anions with the grafted Cu^II complexes on the surface of the SC1 , SC2 , and SC3 supports. The hexametaphosphate anion was selected to prepare two capped materials ( SC1‐mPh and SC3‐mPh ). Studies of the [Ru(bipy)₃]²⁺ dye release from solids SC1‐mPh and SC3‐mPh alone and in the presence of a collection of selected anions (HS^?, F^?, Br^?, Cl^?, I^?, CN^?, HPO₄^2?, AcO^?, citrate, NO₃^2?, HCO₃^?, SO₄^2?, and S₂O₈^2?), amino acids (alanine and histidine), thiol‐containing biomolecules (cysteine, methylcysteine, homocysteine, and glutathione (GSH)), and oxidants (H₂O₂) were performed. None of the chemicals tested, except hydrogen sulphide, was able to induce remarkable cargo delivery in both solids. The observed dye release was ascribed to a demetalation reaction of the C1 and C3 complexes induced by the hydrogen sulphide anion.     

Drug-excipient compatibility studies in binary and ternary mixtures by physico-chemical techniques

This work is part of a systematic study undertaken to find and optimize a general method of detecting the drug-excipient interactions, with the aim of predicting rapidly and inexpensively the long term stability of a pharmaceutical product and speed up its marketing. Here, in particular, the compatibility of haloperidol with several excipients (PVP, magnesium stearate and α-lactose) in binary and ternary mixtures, both as prepared and ball-milled, has been assessed by thermal methods, electron microscopy, IR spectroscopy and X-ray diffraction. The differences between the experimental behaviour of the systems and that expected as weighted average of similarly treated pure components are interaction indicators. The DSC has proven to be, among the selected analytical techniques, the most sensitive and specific in assessing the compatibility. A strong interaction has been observed between PVP and haloperidol. It is favoured by the mechanical stress and is more evident in the composition 20:80. On the contrary, α-lactose and magnesium stearate were found to be compatible with the drug.     

Controlled synthesis of gold nanostars by using a zwitterionic surfactant

By replacing cetyltrimethylammonium bromide (CTAB) with the zwitterionic lauryl sulfobetaine (LSB) surfactant in the classical seed-growth synthesis, monocrystalline gold nanostars (m-NS) and pentatwinned gold asymmetric nanostars (a-NS) were obtained instead of nanorods. The main product under all synthetic conditions was a-NS, which have branches with high aspect ratios (AR), thus leading to LSPR absorptions in the 750-1150?nm range. The percentage of m-NS versus a-NS, the aspect ratio of the a-NS branches, and consequently the position of their LSPR absorption can be finely tuned simply by regulating the concentration of reductant, the concentration of surfactant, or the concentration of the "catalytic" Ag(+) cation. The m-NS have instead shorter and larger branches, the AR of which is poorly influenced by synthetic conditions and displays an LSPR positioned around 700?nm. A growth mechanism that involves the direct contact of the sulfate moiety of LSB on the surface of the nano-object is proposed, thereby implying preferential coating of the {111} Au faces with weak interactions. Consistent with this, we also observed the straightforward complete displacement of the LSB surfactant from the surface of the nanostars. This was obtained by the simple addition of thiols in aqueous solution to yield extremely stable coated a-NS and m-NS that are resistant to highly acidic, basic, and in similar to in vivo conditions.     

Spectroscopy of thulium and holmium heavily doped tellurite glasses

In this study, we report spectroscopic properties of Tm³⁺ and Ho³⁺ codoped tellurite glasses over a wide dopant concentration range in order to assess their potential laser performance under 790 nm diode laser excitation. The impact of Tm³⁺ and Ho³⁺ concentrations is investigated to identify specific candidates for fiber laser operation. The emission cross section is calculated and discussed, as well as the gain coefficient of this type of glasses. Energy transfer microparameters and critical ion distances are determined for ³H₄, ³F₄ (Tm³⁺), and ⁵I₇ (Ho³⁺) emission levels in the framework of diffusion-limited regime and dipole–dipole interaction. We also report thermal properties of tested glasses.     

Blockade of stress-induced increase of glutamate release in the rat prefrontal/frontal cortex by agomelatine involves synergy between melatonergic and 5-HT2C receptor-dependent pathways

Background

Agomelatine is a melatonergic receptor agonist and a 5HT_2C receptor antagonist that has shown antidepressant efficacy. In order to analyze separately the effect of the two receptorial components, rats were chronically treated with agomelatine, melatonin (endogenous melatonergic agonist), or S32006 (5-HT_2C antagonist), and then subjected to acute footshock-stress.

Results

Only chronic agomelatine, but not melatonin or S32006, completely prevented the stress-induced increase of glutamate release in the rat prefrontal/frontal cortex.

Conclusions

These results suggest a potential synergy between melatonergic and serotonergic pathways in the action of agomelatine.