All-perylene-derivative for white light emitting diodes.

An organic-based bright white light emitting compound, namely Tb(H3PTC)3 [H4PTC = perylene-3,4,9,10-tetracarboxylic acid], able to be used as part of a white diode and as a part of a RGB system that can withstand high temperatures (∼700 K), is developed using perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and terbium(iii) nitrate pentahydrate as precursors by hydrothermal synthesis. Using PTCDA as the red emitter and the new derivative of it, Tb(H3PTC)3, as the blue-green emitter, along with a common deep blue LED can form a RGB system for display technologies, around room temperature. Temperature-dependent photoluminescence properties of the Tb(H3PTC)3 compound are also investigated for the involved excitonic-emission processes and the respective recombination lifetimes. The terbium(iii) complex was prepared using a procedure that is reproducible, easily modifiable, inexpensive, and environmentally friendly, opening new pathways for its large-scale applications. Unlike PTCDA, Tb(H3PTC)3 has been shown to be soluble in N-methyl-2-pyrrolidone (NMP) as well as in dilute aqueous solutions of this organic solvent in a straightforward procedure. The light emission properties are intimately correlated with the molecular structure and electronic properties of Tb(H3PTC)3 elucidated by experimental results of X-ray Absorption Near Edge Spectroscopy (XANES), Extended X-ray Absorption Fine Structure (EXAFS) and Density Functional Theory (DFT) calculations. A bright fluorescence yield is attained with a small amount of material either in solution or in solid form showing its potential to be used in state-of-the-art organic optoelectronic devices.

Recovery of Arapaima sp. populations by community-based management in floodplains of the Purus River, Amazon.

In the present study a unique dataset on population abundance in various community-based management (CBM) and non-CBM areas is analysed to address the question of whether CBM can recover overexploited populations of Arapaima sp. in river-floodplain ecosystems. All non-CBM areas possessed depleted Arapaima sp. populations with a mean density of 0·01 individuals ha(-1) . Arapaima sp. population densities in all CBM areas changed over time from depleted to overexploited or well managed status, with a mean rate of increase of 77% year(-1) . Rates of Arapaima sp. population recovery in CBM areas differed, probably reflecting differences in ecosystem productivity and compliance with management regulations. These results indicate that CBM schemes can be effective tools for the recovery and conservation of fish populations with non-migratory life cycles in tropical river-floodplain ecosystems.

Leukopenia in kidney transplant patients with the association of valganciclovir and mycophenolate mofetil.

Cytomegalovirus (CMV) is the most common viral infection after transplantation. Valganciclovir (VGC) is established for prophylaxis and treatment of CMV infections, but leukopenia which appears in 10% to 13% (severe in 4.9%) is the principal side effect. We have recently noted an increased incidence of leukopenia and severe neutropenia among our renal transplant patients and thought to identify the associated factors. We conducted a retrospective analysis of all kidney transplantations performed between January 2005 and December 2006. All patients received mycophenolate mofetil (MMF), tacrolimus, and steroids. VGC was used for targeted prophylaxis and preemptive therapy of CMV infection, with doses adjusted to renal function. Of the 64 patients undergoing renal transplantation 13 (20.3%) developed leukopenia within 3 +/- 2 months after transplantation with severe neutropenia in 5 (7.8%). All patients were on MMF and VGC (VGC 605 +/- 296 mg/d). Leukopenia was significantly associated with simultaneous liver-kidney transplantation and with second kidney transplantations (P < .01). The incidence of leukopenia was higher among patients under VGC since day 1 of transplantation (P = .008) with maximal incidence observed among patients prescribed 900 mg/d as opposed to those on lower doses (P < .01). There was no increase in CMV infection among patients with a low dose of VGC. No patient developed clinical CMV disease. In conclusion, VGC prophylaxis was associated with an increased frequency of leukopenia on MMF-tacrolimus treated patients or regimens. Low-dose VGC for CMV prophylaxis appeared to be as effective as high-dose treatment, and associated less frequently with leukopenia and neutropenia.

Use of gauze cylinders in laparoscopic cholecystectomy: a technical alternative.

Difficulties involved in hemostasis, drying structures for better visualization, and performing blunt dissection during laparoscopic surgery for gallbladder removal motivated the development of a technique that would permit these activities to be carried out in a practical and safe manner. The method consists of placing a prepared gauze cylinder in the peritoneal cavity, where it can be useful in various situations, as is also the case for open surgeries. We report here the technique and advantages of using gauze in laparoscopic cholecystectomy.