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The existing mechanisms proposed to explain the phosphorescence of SrAl2O4:Eu²⁺,Dy³⁺ and related phosphors were found to be inconsistent with a number of important experimental and theoretical observations. We formulated a new mechanism of phosphorescence on the basis of the facts that the d orbitals of Eu²⁺ are located near the conduction band bottom of SrAl2O4, that the Eu²⁺ concentration decreases during UV excitation, and that trace amounts of Eu³⁺ are always present in these phosphors. In our mechanism, some Eu²⁺ ions are oxidized to Eu³⁺ under UV, and the released electrons are trapped at the oxygen vacancy levels located in the vicinity of the photogenerated Eu³⁺ cations. The phosphorescence arises from the recombination of these trapped electrons around the photogenerated Eu³⁺ sites with emission at 520 nm. The codopant Dy³⁺ enhances the phosphorescence by increasing the number and the depth of electron traps, and the codopant B³⁺ enhances the phosphorescence by increasing the depth of electron traps. We also probed the origin of another emission at 450 nm of SrAl2O4:Eu²⁺ that occurs at low temperatures. Our analysis indicates that this emission is caused by a charge transfer from oxygen to Eu³⁺ cations and is associated with a hole trapping.

Lanthanide phosphate nanocrystals exhibiting the rhabdophane-type structure and mean particle sizes below 10 nm are synthesized by hydrolysis of an aqueous mixture of sodium tripolyphosphate (Na5P3O10) and lanthanide salts. ³¹P NMR studies show that polyphosphate groups act both as a source of orthophosphate and as complexing agents to, respectively, crystallize and stabilize LnPO4·xH2O (x ≈ 0.7) nanoparticles. In the ternary system (Ln = La, Ce, and Tb), polyphosphate-capped particles form well-dispersed and highly luminescent aqueous colloids which are promising for applications in light-emitting devices.

Persistent nitroxides and their corresponding alkoxyamines are important regulators of living radical polymerization. Here we describe the synthesis of β-phosphorus nitroxides bearing a β-hydrogen, that present very interesting properties for the control of the radical polymerization of styrenes, acrylates and other monomers. A large series of alkoxyamines derived from these nitroxides was prepared, and Electron Spin Resonance (ESR) was used to determine both the temperature (Tc) and the rate constant (kd) for their homolysis. For the whole series of alkoxyamines (27 compounds), a very good linear correlation was found between Tc and logkd. Satisfactory linear correlations were found between Tc and calculated (PM3 method) Bond Dissociation Energy (BDE) of the NO-C bond, for series of alkoxyamines with the same type of leaving radical. The characteristics of free radical polymerization of styrene carried out in the presence of these new nitroxides and alkoxyamines will be discussed.

Trialkylhydroxylamines and persistent nitroxide radicals are important regulators of living radical polymerizations. Since the polymerization times decrease with increasing rate of the C−O-bond dissociation between the polymer chain and the nitroxide moiety, the factors influencing the homolysis rate constants are of considerable interest. Here, data are presented for 27 model trialkylhydroxylamines in solution containing TMIO, TEMPO, TEDIO, TIPNO, DBNO, SG1, and similar nitroxide groups and primary, secondary and tertiary carbon-centered leaving radicals R. On the average, the frequency factor is A = 2.6 × 10¹⁴ s^-1, and the activation energies reveal steric effects of both the radical and the nitroxide substituents. Moreover, they increase strongly with increasing C−H-bond energy of the corresponding R−H compounds, and for the same R, decrease in the order TMIO > TEMPO > TIPNO > TEDIO > SG1 ≈ DBNO. The rate constants agree well with data reported for polymerizing systems, and increments are given for radical and nitroxide substitutions which should facilitate predictions for other alkoxyamines.

•Discussion of the backgrounds and challenges of using EPAs as an assessment and learning tool in surgery;•Evaluation of the efficiency and safety of elective laparoscopic cholecystectomy in different level of surgical trainees•Specifically, we have shown that early surgical trainees take significantly longer to perform an elective laparoscopic cholecystectomy, with comparable complication rates as their senior counterparts•Discussion the steep learning curve of the procedure in early surgical trainees;•Establishment of elective laparoscopic cholecystectomy as an appropriate EPAs in early surgical trainees

Galectin (Gal) 1 is a hypoxia-regulated proangiogenic factor that also directly participates in glioblastoma cell migration. To determine how Gal-1 exerts its proangiogenic effects, we investigated Gal-1 signaling in the human Hs683 glioblastoma cell line. Galectin 1 signals through the endoplasmic reticulum transmembrane kinase/ribonuclease inositol-requiring 1α, which regulates the expression of oxygen-regulated protein 150. Oxygen-regulated protein 150 controls vascular endothelial growth factor maturation. Galectin 1 also modulates the expression of 7 other hypoxia-related genes (i.e. CTGF, ATF3, PPP1R15A, HSPA5, TRA1, and CYR61) that are implicated in angiogenesis. Decreasing Gal-1 expression in Hs683 orthotopic xenografts in mouse brains by siRNA administration impaired endoplasmic reticulum stress and enhanced the therapeutic benefits of the proautophagic drug temozolomide. These results suggest that decreasing Gal-1 expression (e.g. through brain delivery of nonviral infusions of anti-Gal-1 siRNA in patients) can represent an additional therapeutic strategy for glioblastoma.