2,842 research outputs found
Magnetically controlled exciton transfer in hybrid quantum dot-quantum well nanostructures
A magnetophotoluminescence study of the carrier transfer with hybrid
InAs/GaAs quantum dot(QD)-InGaAs quantum well (QW) structures is carried out
where we observe an unsual dependence of the photoluminescence (PL) on the GaAs
barrier thickness at strong magnetic field and excitation density. For the case
of a thin barrier the QW PL intensity is observed to increase at the expense of
a decrease in the QD PL intensity. This is attributed to changes in the
interplane carrier dynamics in the QW and the wetting layer (WL) resulting from
increasing the magnetic field along with changes in the coupling between QD
excited states and exciton states in the QW and the WL
Polarization sensitive spectroscopy of charged Quantum Dots
We present an experimental and theoretical study of the polarized
photoluminescence spectrum of single semiconductor quantum dots in various
charge states. We compare our high resolution polarization sensitive spectral
measurements with a new many-carrier theoretical model, which was developed for
this purpose. The model considers both the isotropic and anisotropic exchange
interactions between all participating electron-hole pairs. With this addition,
we calculate both the energies and polarizations of all optical transitions
between collective, quantum dot confined charge carrier states. We succeed in
identifying most of the measured spectral lines. In particular, the lines
resulting from singly-, doubly- and triply- negatively charged excitons and
biexcitons. We demonstrate that lines emanating from evenly charged states are
linearly polarized. Their polarization direction does not necessarily coincide
with the traditional crystallographic direction. It depends on the shells of
the single carriers, which participate in the recombination process.Comment: 11 pages, 9 figures. Revised versio
Influence Of Nanopolymers With Different EndâFunctionalities On Platelets And Coagulation. An ExâVivo Study
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106058/1/jth03252.pd
The aerodynamic challenges of the design and development of the space shuttle orbiter
The major aerodynamic design challenge at the beginning of the United States Space Transportation System (STS) research and development phase was to design a vehicle that would fly as a spacecraft during early entry and as an aircraft during the final phase of entry. The design was further complicated because the envisioned vehicle was statically unstable during a portion of the aircraft mode of operation. The second challenge was the development of preflight aerodynamic predictions with an accuracy consistent with conducting a manned flight on the initial orbital flight. A brief history of the early contractual studies is presented highlighting the technical results and management decisions influencing the aerodynamic challenges. The configuration evolution and the development of preflight aerodynamic predictions will be reviewed. The results from the first four test flights shows excellent agreement with the preflight aerodynamic predictions over the majority of the flight regimes. The only regimes showing significant disagreement is confined primarily to early entry, where prediction of the basic vehicle trim and the influence of the reaction control system jets on the flow field were found to be deficient. Postflight results are analyzed to explain these prediction deficiencies
Surface atomic arrangement of aluminum ultra-thin layers grown on Si(111)
Surface atomic arrangement and physical properties of aluminum ultrathin layers on c-Si(111)-7 à 7 and hydrogen-terminated c-Si(111)-1 à 1 surfaces deposited using molecular beam epitaxy were investigated. X-ray photoelectron spectroscopy spectra were collected in two configurations (take-off angle of 0° and 45°) to precisely determine the surface species. Moreover, 3D atomic force microscopy (AFM) images of the air-exposed samples were acquired to investigate the clustering formations in film structure. The deposition of the Al layers was monitored in situ using a reflection high-energy electron diffraction (RHEED) experiments to confirm the surface crystalline structure of the c-Si(111). The analysis of the RHEED patterns during the growth process suggests the settlement of aluminum atoms in Al(111)-1 à 1 clustered formations on both types of surfaces. The surface electrical conductivity in both configurations was tested against atmospheric oxidation. The results indicate differences in conductivity based on the formation of various alloys on the surface.This research was partially funded by the German Jordanian University in Jordan through seed grant (SBSH 02/2021)
Genetic constraint at single amino acid resolution in protein domains improves missense variant prioritisation and gene discovery
: Background: One of the major hurdles in clinical genetics is interpreting the clinical consequences associated with germline missense variants in humans. Recent significant advances have leveraged natural variation observed in large-scale human populations to uncover genes or genomic regions that show a depletion of natural variation, indicative of selection pressure. We refer to this as âgenetic constraintâ. Although existing genetic constraint metrics have been demonstrated to be successful in prioritising genes or genomic regions associated with diseases, their spatial resolution is limited in distinguishing pathogenic variants from benign variants within genes. Methods: We aim to identify missense variants that are significantly depleted in the general human population. Given the size of currently available human populations with exome or genome sequencing data, it is not possible to directly detect depletion of individual missense variants, since the average expected number of observations of a variant at most positions is less than one. We instead focus on protein domains, grouping homologous variants with similar functional impacts to examine the depletion of natural variations within these comparable sets. To accomplish this, we develop the Homologous Missense Constraint (HMC) score. We utilise the Genome Aggregation Database (gnomAD) 125 K exome sequencing data and evaluate genetic constraint at quasi amino-acid resolution by combining signals across protein homologues. Results: We identify one million possible missense variants under strong negative selection within protein domains. Though our approach annotates only protein domains, it nonetheless allows us to assess 22% of the exome confidently. It precisely distinguishes pathogenic variants from benign variants for both early-onset and adult-onset disorders. It outperforms existing constraint metrics and pathogenicity meta-predictors in prioritising de novo mutations from probands with developmental disorders (DD). It is also methodologically independent of these, adding power to predict variant pathogenicity when used in combination. We demonstrate utility for gene discovery by identifying seven genes newly significantly associated with DD that could act through an altered-function mechanism. Conclusions: Grouping variants of comparable functional impacts is effective in evaluating their genetic constraint. HMC is a novel and accurate predictor of missense consequence for improved variant interpretation
Evaluation of the psychometric properties of the SF-36 health survey for use among Turkish and Moroccan ethnic minority populations in the Netherlands
Purpose: To evaluate the psychometrics of the SF-36 Health Survey among Turkish and Moroccan ethnic minority populations in the Netherlands and to compare the results to those based on the indigenous Dutch population. Methods: Data were derived from the Second Dutch National Survey of General Practice. In total, SF-36 data were available for 409 Turkish, 377 Moroccan, and 9,628 Dutch respondents. Language subgroup analyses were performed for the Turkish (n = 162) and Moroccan-Arabic (n = 52) versions of the SF-36. Psychometric properties were evaluated by descriptive statistics, factor analysis, internal consistency estimates, known-group comparisons, and differential item function (DIF) analysis. Results Low levels of missing SF-36 data were observed across all groups. Confirmatory factor analysis supported the hypothesized SF-36 scale structure for the Dutch and Turkish group, but high correlations between the MH and VT factors were observed in the Moroccan group. All Cronbachâs alpha coefficients were above 0.70, except for
the Vitality scale in the Moroccan group and the Vitality and Social Functioning scales in the Moroccan-Arabic language subgroup. Known-groups validity was found across samples using age, sex, education, and comorbidity as grouping variables, but not marital status. Some evidence for DIF was found in both ethnic group samples. Conclusions: The results generally support the use of the SF-36 for general population research among Turkish and Moroccan ethnic minorities in the Netherlands. Additional studies are needed to confirm the psychometrics of the questionnaire when used among these populations in other Western European countries. (aut. ref.
Synthesis, structural characterization, antimicrobial and cytotoxic effects of aziridine, 2-aminoethylaziridine and azirine complexes of copper(II) and palladium(II).
The synthesis, spectroscopic and X-ray structural characterization of copper(II) and palladium(II) complexes with aziridine ligands as 2-dimethylaziridine HNCH2CMe2 (a), the bidentate N-(2-aminoethyl)aziridines C2H4NC2H4NH2 (b) or CH2CMe2NCH2CMe2NH2 (c) as well as the unsaturated azirine NCH2CPh (d) are reported. Cleavage of the cyclometallated Pd(II) dimer [ÎŒ-Cl(C6H4CHMeNMe2-C,N)Pd]2 with ligand a yielded compound [Cl(NHCH2CMe2)(C6H4CHMe2NMe2-C,N)Pd] (1a). The reaction of the aziridine complex trans-[Cl2Pd(HNC2H4)2] with an excess of aziridine in the presence of AgOTf gave the ionic chelate complex trans-[(C2H4NC2H4NH2-N,NâČ)2Pd](OTf)2 (2b) which contains the new ligand b formed by an unexpected insertion and ring opening reaction of two aziridines (âaziridine dimerizationâ). CuCl2 reacted in pure HNC2H4 or HNCH2CMe2 (b) again by âdimerizationâ to give the tris-chelated ionic complex [Cu(C2H4NC2H4NH2-N,NâČ)3]Cl2 (3b) or the bis-chelated complex [CuCl(C2H2Me2NC2H2Me2NH2-N,NâČ)2]Cl (4c). By addition of 2H-3-phenylazirine (d) to PdCl2, trans-[Cl2Pd(NCH2CPh)2] (5d) was formed. All new compounds were characterized by NMR, IR and mass spectra and also by X-ray structure analyses (except 3b). Additionally the cytotoxic effects of these complexes were examined on HL-60 and NALM-6 human leukemia cells and melanoma WM-115 cells. The antimicrobial activity was also determined. The growth of Gram-positive bacterial strains (S. aureus, S. epidermidis, E. faecalis) was inhibited by almost all tested complexes at the concentrations of 37.5â300.0 ÎŒg mLâ1. However, MIC values of complexes obtained for Gram-negative E. coli and P. aeruginosa, as well as for C. albicans yeast, mostly exceeded 300 ÎŒg mLâ1. The highest antibacterial activity was achieved by complexes 1a and 2b. Complex 2b also inhibited the growth of Gram-negative bacteria.
Graphical abstract: Synthesis, structural characterization, antimicrobial and cytotoxic effects of aziridine, 2-aminoethylaziridine and azirine complexes of copper(ii) and palladium(ii
Response shift due to diagnosis and primary treatment of localized prostate cancer: a then-test and a vignette study
Aim Whether a prostate cancer diagnosis induces response shift has not been established so far. Therefore, we assessed response shift in men who were diagnosed with localized prostate cancer.
Patients and methods Out of 3,892 men who completed a questionnaire before screening, 82 were subsequently diagnosed with prostate cancer. Response shift was assessed in 52 (response 63%) by the then-test (EuroQol self-rating of health, Short-Form 36 mental health and vitality) and a novel method: rating of vignettes relating to side effects of prostate cancer treatment (urinary, bowel and erectile dysfunction). Three then-tests were conducted: two referencing pre-diagnosis (measured pre
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