Size quantization effects in InAs self-assembled quantum dots

3 páginas, 3 figuras. PACS: 73.21.-b; 78.55.Cr; 78.66.Fd; 72.40.+w; 68.35.Ct; 73.40.KpWe study size quantization effects in InAs self-assembled quantum dots (QDs) that are embedded in GaAs. Using capacitance, photoluminescence and photovoltage spectroscopy, we correlate the measured quantized level energies with the quantum dot sizes and densities obtained from transmission electron microscopy. With increasing dot size, we observe a strong redshift of the QD features in all our data. In the capacitance spectra, a band gap renormalization of the two-dimensional wetting layer system appears when the first excited QD state crosses the wetting layer ground state. The relative size dependence and absolute energetic position of the QD transitions determined with photoluminescence provide some information about the influence of lateral confinement and height of the QD.This work was supported by QUEST, a NSF science and technology center (Grant No. DMR91-20007), the Alexander von Humboldt Foundation (KHS), and the Brazilian agency CNPq (GMR).Peer reviewe

Labour epidural analgesia and anti-infectious management of the neonate: a meta-analysis

BACKGROUND: A known side effect of labour epidural analgesia (EDA) is maternal fever. It is unclear whether this has effects on the anti-infectious management of the neonate. METHODS: A systematic literature search and a hand search of abstract publications were conducted. Studies reporting sepsis evaluation or antibiotic treatment were further assessed. For meta-analysis, risk ratio (RR) and 95% confidence interval (CI) were calculated using the random effects model. RESULTS: Five relevant articles reporting on 4667 parturients were identified; three were observational studies and two were randomised controlled trials (RCT). The RR for sepsis workup of all studies analysed together was 2.58 (95% CI, 1.06-6.27, P=0.04). The RR for antibiotic treatment of the neonate was 2.76 (95% CI, 1.20-6.31, P=0.02). When considering the RCTs alone, the RRs for sepsis evaluation and antimicrobial treatment were still significantly elevated. DISCUSSION: Our data suggest that EDA-related maternal hyperthermia results in an increased likelihood of sepsis workup and antibiotic treatment of the infant. A crucial question is whether EDA-related maternal hyperthermia is truly infectious. If not, administration of antibiotics would not be justified and may be dangerous.status: publishe

Insertion of an intrathecal catheter following accidental dural puncture:a meta-analysis

<p>Background: Inserting an intrathecal catheter after accidental dural puncture in parturients to prevent postdural puncture headache is becoming increasingly popular. We aimed to identify relevant published articles investigating this intervention and subject data to a meta-analysis.</p><p>Methods: A systematic literature search was performed, paralleled by a hand search of abstract publications. Studies that reported. the dichotomous outcome parameters postdural puncture headache or need for an epidural blood patch were considered eligible. Risk ratios with 95% confidence intervals were calculated.</p><p>Results: We identified nine reports investigating placement of intrathecal catheters after accidental dural puncture. The risk ratio for an epidural blood patch after intrathecal catheter insertion was 0.64 (95% CI 0.49-0.84, P = 0.001). The risk ratio for postdural puncture headache was 0.82 (95% CI 0.67-1.01, P = 0.06).</p><p>Discussion: Inserting an intrathecal catheter significantly reduced the risk for an epidural blood patch; the incidence of postdural puncture headache was reduced but not significantly. Accidental dural puncture is a rare complication and therefore trials on intervention need to include a large number of patients which is time-consuming and costly. Intrathecal catheterisation is a promising approach for the prevention of postdural puncture headache and should be evaluated further. This intervention has additional benefits including a reduced risk of repeat dural puncture, rapid onset of action and use for anaesthesia. (C) 2012 Elsevier Ltd. All rights reserved.</p>