A Comparison of Magnesium and Beryllium Acceptors in GaN Grown by rf-Plasma Assisted Molecular Beam Epitaxy

ABSTRACT Step-doped structures of both magnesium and beryllium were grown in GaN and analyzed using secondary ion mass spectrometry. Dopant incorporation was studied as a function of substrate temperature and dopant flux for Ga-polarity and N-polarity GaN. Incorporation is different for each polarity, with Mg incorporating by up to a factor of 20 times more (30 times more with atomic hydrogen) on the Ga-face, while Be incorporates more readily on the N-face. The effect of atomic hydrogen on the incorporation kinetics of both Mg and Be is also discussed. Mg and Be both undergo surface segregation during growth. Photoluminescence measurements suggest that Be is a p-type dopant with an optical activation energy of approximately 100 meV

Histology of the Pharyngeal Constrictor Muscle in 22q11.2 Deletion Syndrome and Non-Syndromic Children with Velopharyngeal Insufficiency

Plastic surgeons aim to correct velopharyngeal insufficiency manifest by hypernasal speech with a velopharyngoplasty. The functional outcome has been reported to be worse in patients with 22q11.2 deletion syndrome than in patients without the syndrome. A possible explanation is the hypotonia that is often present as part of the syndrome. To confirm a myogenic component of the etiology of velopharyngeal insufficiency in children with 22q11.2 deletion syndrome, specimens of the pharyngeal constrictor muscle were taken from children with and without the syndrome. Histologic properties were compared between the groups. Specimens from the two groups did not differ regarding the presence of increased perimysial or endomysial space, fiber grouping by size or type, internalized nuclei, the percentage type I fibers, or the diameters of type I and type II fibers. In conclusion, a myogenic component of the etiology of velopharyngeal insufficiency in children with 22q11.2 deletion syndrome could not be confirmed

In Search of the Optimal Surgical Treatment for Velopharyngeal Dysfunction in 22q11.2 Deletion Syndrome: A Systematic Review

<div><h3>Background</h3><p>Patients with the 22q11.2 deletion syndrome (22qDS) and velopharyngeal dysfunction (VPD) tend to have residual VPD following surgery. This systematic review seeks to determine whether a particular surgical procedure results in superior speech outcome or less morbidity.</p> <h3>Methodology/ Principal Findings</h3><p>A combined computerized and hand-search yielded 70 studies, of which 27 were deemed relevant for this review, reporting on a total of 525 patients with 22qDS and VPD undergoing surgery for VPD. All studies were levels 2c or 4 evidence. The methodological quality of these studies was assessed using criteria based on the Cochrane Collaboration's tool for assessing risk of bias. Heterogeneous groups of patients were reported on in the studies. The surgical procedure was often tailored to findings on preoperative imaging. Overall, 50% of patients attained normal resonance, 48% attained normal nasal emissions scores, and 83% had understandable speech postoperatively. However, 5% became hyponasal, 1% had obstructive sleep apnea (OSA), and 17% required further surgery. There were no significant differences in speech outcome between patients who underwent a fat injection, Furlow or intravelar veloplasty, pharyngeal flap pharyngoplasty, Honig pharyngoplasty, or sphincter pharyngoplasty or Hynes procedures. There was a trend that a lower percentage of patients attained normal resonance after a fat injection or palatoplasty than after the more obstructive pharyngoplasties (11–18% versus 44–62%, p = 0.08). Only patients who underwent pharyngeal flaps or sphincter pharyngoplasties incurred OSA, yet this was not statistically significantly more often than after other procedures (p = 0.25). More patients who underwent a palatoplasty needed further surgery than those who underwent a pharyngoplasty (50% versus 7–13%, p = 0.03).</p> <h3>Conclusions/ Significance</h3><p>In the heterogeneous group of patients with 22qDS and VPD, a grade C recommendation can be made to minimize the morbidity of further surgery by choosing to perform a pharyngoplasty directly instead of only a palatoplasty.</p> </div

Potential use of carbon felt in gold hydrometallurgy

The use of carbon felt as a three-dimensional electrode appears to be very promising for the recovery of heavy metals, and toxic compounds removal from dilute solutions, considering its favourable physico-chemical properties : high specific surface area, good fluid permeability and compressibility, chemical inertness and good electrical conductivity. This work presents the contribution of the carbon felt electrode in two different steps of the gold cyanidation recovery process : firstly as a cathode for the electrowinning of gold solution obtained after the elution of loaded carbon; secondly as an anode for the electro-oxidation of cyanide ions present at low concentration (200-300mg/l) in waste streams. In the first case, more than 10 kg of gold per m(2) of felt (2000 kg of gold per m(3) of felt) can be loaded at 400 A/m(2) from dilute gold solutions (30 mg/l Au) with classic Faradic yields (6-12 %) and high overall extraction efficiency (> 90 %). The felt homogeneously loaded with adhesive gold deposit can be smelted in an electric furnace without addition of fluxes since the carbon felt decomposes in gaseous products without formation of ashes. In the second case, the cyanide ion concentration can be lowered to as low as 10 mg/l by electro-oxidation to cyanate form (CNO-) at 400 A/m2 in the anodic compartment of a divided cell. The presence of copper ion significantly improves the current efficiency of this electro-oxidation and sharply reduces the oxidation of the carbon felt. Copper ions accelerate the oxidation rate of free cyanide ions through the formation of easily oxidizable complexes owing to a mechanism in which the Cu-I/Cu-II redox couple acts as an electron transfer mediator. (C) 1999 Elsevier Science Ltd. All rights reserved

Traitement intégré d'effluents industriels difficilement biodégradables par procédés membranaires combinés à différentes techniques destructives

Afin de réduire les coûts et d'améliorer l'efficacité de traitement, les procédés de traitements d'effluents industriels combinent fréquemment différentes techniques de recyclage et d'épuration. Dans cette optique, l'association de techniques électrochimiques, biologiques et de filtration tangentielle contribue à l'amélioration du traitement d'eaux usées industrielles chargées en composés non-biodégradables. Ces composés récalcitrants peuvent être concentrés par filtration tangentielle (MF, UF, NF) en vue d'être valorisés ou traités ultérieurement. Les procédés électrochimiques permettent, quant à eux, une destruction des composés organiques récalcitrants. L'intégration des techniques électrochimiques et de filtration tangentielle au niveau d'une station d'épuration classique améliore son fonctionnement tout en offrant la perspective d'une valorisation interne ou externe des effluents