393 research outputs found
Quantum interference in exciton-Mn spin interactions in a CdTe semiconductor quantum dot
We show theoretically and experimentally the existence of a new quantum
interference(QI) effect between the electron-hole interactions and the
scattering by a single Mn impurity. Theoretical model, including
electron-valence hole correlations, the short and long range exchange
interaction of Mn ion with the heavy hole and with electron and anisotropy of
the quantum dot, is compared with photoluminescence spectroscopy of CdTe dots
with single magnetic ions. We show how design of the electronic levels of a
quantum dot enable the design of an exciton, control of the quantum
interference and hence engineering of light-Mn interaction.Comment: 11 pages, 4 figures, submitted to PR
Optical manipulation of a single Mn spin in a CdTe-based quantum dot
A system of two coupled CdTe quantum dots, one of them containing a single Mn
ion, was studied in continuous wave and modulated photoluminescence,
photoluminescence excitation, and photon correlation experiments. Optical
writing of information in the spin state of the Mn ion has been demonstrated,
using orientation of the Mn spin by spin-polarized carriers transferred from
the neighbor quantum dot. Mn spin orientation time values from 20 ns to 100 ns
were measured, depending on the excitation power. Storage time of the
information in the Mn spin was found to be enhanced by application of a static
magnetic field of 1 T, reaching hundreds of microseconds in the dark. Simple
rate equation models were found to describe correctly static and dynamical
properties of the system.Comment: 4 pages, 3 figure
Dynamics of Charge Leakage From Self-assembled CdTe Quantum Dots
We study the leakage dynamics of charge stored in an ensemble of CdTe quantum
dots embedded in a field-effect structure. Optically excited electrons are
stored and read out by a proper time sequence of bias pulses. We monitor the
dynamics of electron loss and find that the rate of the leakage is strongly
dependent on time, which we attribute to an optically generated electric field
related to the stored charge. A rate equation model quantitatively reproduces
the results.Comment: 4 pages, submitted to Applied Physics Letter
Isolation of New Secondary Metabolites from New Zealand Marine Invertebrates
This study describes the isolation and structure elucidation of several known and 13 new compounds from New Zealand marine organisms. Furthermore, it describes the development of a digital mask program for the analysis of HSQC
spectra of crude sponge extracts. This was used as a screening tool to identify secondary metabolite producers that warranted further analysis. As reports of metabolites from New Zealand nudibranchs are poorly represented
in the literature, a study of five New Zealand nudibranch species was undertaken. These coloured and seemingly undefended nudibranchs are known to concentrate or sequester toxic metabolites from their prey, facilitating rapid
isolation and structure elucidation of these metabolites. This study resulted in the isolation of a variety of metabolite classes; two new compounds, 13alpha- acetoxypukalide diol (30) and lopholide diol (31) from the nudibranch Tritonia incerta, are described. Examination of the sponge Raspailia agminata resulted in the isolation of a novel family of partially acetylated glycolipids which contain up to six glucose residues. The chromatographic separation of these compounds was a challenge due to the similarity of the congeners and their lack of a chromophore. MSguided isolation eventually led to the purification of agminosides A-E (145-149). An unidentified sponge of the order Dictyoceratida was found to contain a new isomer (186) of the known sesterterpene variabilin. As variabilin-type
compounds are predominantly found from sponges of the family Irciniidae, the unidentified sponge is most likely an irciniid. In addition, the sponge contained two prenylated quinones, one of which, 189, is a new isomer of a known sponge
metabolite. The sponge Darwinella oxeata contained four new nitrogenous diterpenes of
the aplysulphurane (rearranged spongian) skeleton, oxeatamide A (214), isooxeatamide
A (215), oxeatamide A 23-methyl ester (216) and oxeatamide B (217)
Who receives treatment for alcohol use disorders in the European Union? A cross-sectional representative study in primary and specialized health care
Background
Alcohol use disorders (AUDs) are highly prevalent in Europe, but only a minority of those affected receive treatment. It is therefore important to identify factors that predict treatment in order to reframe strategies aimed at improving treatment rates.
Methods
Representative cross-sectional study with patients aged 18\u201364 from primary health care (PC, six European countries, n = 8476, data collection 01/13\u201301/14) and from specialized health care (SC, eight European countries, n = 1762, data collection 01/13\u201303/14). For descriptive purposes, six groups were distinguished, based on type of DSM-IV AUD and treatment setting. Treatment status (yes/no) for any treatment (model 1), and for SC treatment (model 2) were main outcome measures in logistic regression models.
Results
AUDs were prevalent in PC (12-month prevalence: 11.8%, 95% confidence interval (CI): 11.2\u201312.5%), with 17.6% receiving current treatment (95%CI: 15.3\u201319.9%). There were clear differences between the six groups regarding key variables from all five predictor domains. Prediction of any treatment (model 1) or SC treatment (model 2) was successful with high overall accuracy (both models: 95%), sufficient sensitivity (model 1: 79%/model 2: 76%) and high specificity (both models: 98%). The most predictive single variables were daily drinking level, anxiety, severity of mental distress, and number of inpatient nights during the last 6 months.
Conclusions
Variables from four domains were highly predictive in identifying treatment for AUD, with SC treatment groups showing very high levels of social disintegration, drinking, comorbidity and functional losses. Earlier intervention and formal treatment for AUD in PC should be implemented to reduce these high levels of adverse outcomes
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