138 research outputs found

    From the artificial atom to the Kondo-Anderson model: Orientation-dependent magnetophotoluminescence of charged excitons in InAs quantum dots

    Get PDF
    We present a magnetophotoluminescence study on neutral and charged excitons confined to InAs/GaAs quantum dots. Our investigation relies on a confocal microscope that allows arbitrary tuning of the angle between the applied magnetic field and the sample growth axis. First, from experiments on neutral excitons and trions, we extract the in-plane and on-axis components of the Landé tensor for electrons and holes in the s shell. Then, based on the doubly negatively charged exciton magnetophotoluminescence, we show that the p-electron wave function spreads significantly into the GaAs barriers. We also demonstrate that the p-electron g factor depends on the presence of a hole in the s shell. The magnetic field dependence of triply negatively charged excitons photoluminescence exhibits several anticrossings, as a result of coupling between the quantum dot electronic states and the wetting layer. Finally, we discuss how the system evolves from a Kondo-Anderson exciton description to the artificial atom model when the orientation of the magnetic field goes from Faraday to Voigt geometry.We acknowledge funding from the EPSRC. B.V.H. also thanks the Hitachi Cambridge Laboratory for additional fund- ing. P.C. acknowledges financial support from the European Union Seventh Framework Programme under Grant agreement No. 265073

    Parents' expectations of the outpatient care for daytime urinary incontinence in children:A qualitative study

    Get PDF
    INTRODUCTION: Daytime urinary incontinence (UI) can have an enormous impact on a child's life, lowering both self-esteem and quality of life. Although most children start therapy after their first visit to our outpatient clinic, no studies have reported on parents' or patients' expectations of care for daytime UI in this setting. OBJECTIVE: We aimed to explore the expectations of the parents of children referred to an outpatient clinic for daytime UI. STUDY DESIGN: This was a qualitative study that involved performing semi-structured interviews with the parents of children who had been referred for daytime UI (with or without nocturnal enuresis). Interviews took place between July 2018 and October 2018 and continued until saturation was reached. The results were transcribed verbatim and analyzed according to Giorgi's strategy of phenomenological data analysis. RESULTS: Nine parents of children, aged 5-12 years old, were interviewed, revealing "(Experienced) Health," Self-management," and "Social Impact" as the main themes that influenced parental expectations. All parents wanted to know if there was a medical explanation for UI, some were satisfied when diagnostics revealed no underlying condition, and others wanted treatment. Parents expressed no preferences about diagnostics or the content and duration of treatment, but they hoped that any previously attempted ineffective steps would not be repeated. Some parents defined treatment success as their child becoming completely dry, but most stated that learning coping strategies was more important. DISCUSSION: This is the first study to explore the expectations of parents when attending outpatient care for children with daytime UI. We employed a strong theoretical framework with a clear interview guide. The main limitations are that we only interviewed parents and that this was a qualitative study, precluding the drawing of firm conclusions. Nevertheless, our results point to the need for quantitative evaluation. CONCLUSION: Expectations seem to be influenced by (experienced) health, efforts at self-management, and the social impact of UI, making it critical that these themes are addressed. It was interesting to note that parents do not always attend outpatient departments with the goal of completely resolving daytime UI. Instead, some only want to know if there is an underlying medical condition or want to reduce the social impact by learning coping mechanisms. Excluding underlying medical conditions may therefore stimulate acceptance of watchful waiting without the need to start treatment

    Destination shapes antibiotic resistance gene acquisitions, abundance increases, and diversity changes in Dutch travelers

    Get PDF
    BACKGROUND: Antimicrobial-resistant bacteria and their antimicrobial resistance (AMR) genes can spread by hitchhiking in human guts. International travel can exacerbate this public health threat when travelers acquire AMR genes endemic to their destinations and bring them back to their home countries. Prior studies have demonstrated travel-related acquisition of specific opportunistic pathogens and AMR genes, but the extent and magnitude of travel\u27s effects on the gut resistome remain largely unknown. METHODS: Using whole metagenomic shotgun sequencing, functional metagenomics, and Dirichlet multinomial mixture models, we investigated the abundance, diversity, function, resistome architecture, and context of AMR genes in the fecal microbiomes of 190 Dutch individuals, before and after travel to diverse international locations. RESULTS: Travel markedly increased the abundance and α-diversity of AMR genes in the travelers\u27 gut resistome, and we determined that 56 unique AMR genes showed significant acquisition following international travel. These acquisition events were biased towards AMR genes with efflux, inactivation, and target replacement resistance mechanisms. Travel-induced shaping of the gut resistome had distinct correlations with geographical destination, so individuals returning to The Netherlands from the same destination country were more likely to have similar resistome features. Finally, we identified and detailed specific acquisition events of high-risk, mobile genetic element-associated AMR genes including qnr fluoroquinolone resistance genes, bla CONCLUSIONS: Our results show that travel shapes the architecture of the human gut resistome and results in AMR gene acquisition against a variety of antimicrobial drug classes. These broad acquisitions highlight the putative risks that international travel poses to public health by gut resistome perturbation and the global spread of locally endemic AMR genes

    Import and spread of extended-spectrum beta-lactamase-producing Enterobacteriaceae by international travellers (COMBAT study): a prospective, multicentre cohort study

    Get PDF
    BACKGROUND: International travel contributes to the dissemination of antimicrobial resistance. We investigated the acquisition of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) during international travel, with a focus on predictive factors for acquisition, duration of colonisation, and probability of onward transmission. METHODS: Within the prospective, multicentre COMBAT study, 2001 Dutch travellers and 215 non-travelling household members were enrolled. Faecal samples and questionnaires on demographics, illnesses, and behaviour were collected before travel and immediately and 1, 3, 6, and 12 months after return. Samples were screened for the presence of ESBL-E. In post-travel samples, ESBL genes were sequenced and PCR with specific primers for plasmid-encoded β-lactamase enzymes TEM, SHV, and CTX-M group 1, 2, 8, 9, and 25 was used to confirm the presence of ESBL genes in follow-up samples. Multivariable regression analyses and mathematical modelling were used to identify predictors for acquisition and sustained carriage, and to determine household transmission rates. This study is registered with ClinicalTrials.gov, number NCT01676974. FINDINGS: 633 (34·3%) of 1847 travellers who were ESBL negative before travel and had available samples after return had acquired ESBL-E during international travel (95% CI 32·1-36·5), with the highest number of acquisitions being among those who travelled to southern Asia in 136 of 181 (75·1%, 95% CI 68·4-80·9). Important predictors for acquisition of ESBL-E were antibiotic use during travel (adjusted odds ratio 2·69, 95% CI 1·79-4·05), traveller's diarrhoea that persisted after return (2·31, 1·42-3·76), and pre-existing chronic bowel disease (2·10, 1·13-3·90). The median duration of colonisation after travel was 30 days (95% CI 29-33). 65 (11·3%) of 577 remained colonised at 12 months. CTX-M enzyme group 9 ESBLs were associated with a significantly increased risk of sustained carriage (median duration 75 days, 95% CI 48-102, p=0·0001). Onward transmission was found in 13 (7·7%) of 168 household members. The probability of transmitting ESBL-E to another household member was 12% (95% CI 5-18). INTERPRETATION: Acquisition and spread of ESBL-E during and after international travel was substantial and worrisome. Travellers to areas with a high risk of ESBL-E acquisition should be viewed as potential carriers of ESBL-E for up to 12 months after return. FUNDING: Netherlands Organisation for Health Research and Development (ZonMw)
    corecore