972 research outputs found
PQL: A Declarative Query Language over Dynamic Biological Schemata
We introduce the PQL query language (PQL) used in the GeneSeek genetic data integration project. PQL incorporates many features of query languages for semi-structured data. To this we add the ability to express metadata constraints like intended semantics and database curation approach. These constraints guide the dynamic generation of potential query plans. This allows a single query to remain relevant even in the presence of source and mediated schemas that are continually evolving, as is often the case in data integration
Microscopic theory of indistinguishable single-photon emission from a quantum dot coupled to a cavity: The role of non-Markovian phonon-induced decoherence
We study the fundamental limit on single-photon indistinguishability imposed
by decoherence due to phonon interactions in semiconductor quantum dot-cavity
QED systems. Employing an exact diagonalization approach we find large
differences compared to standard methods. An important finding is that
short-time non-Markovian effects limit the maximal attainable
indistinguishability. The results are explained using a polariton picture that
yields valuable insight into the phonon-induced dephasing dynamics.Comment: published version, comments are very welcom
Quenching of phonon-induced processes in quantum dots due to electron-hole asymmetries
Differences in the confinement of electrons and holes in quantum dots are
shown to profoundly impact the magnitude of scattering with acoustic phonons in
materials where crystal deformation shifts the conduction and valence band in
the same direction. Using an extensive model that includes the non-Markovian
nature of the phonon reservoir, we show how the effect may be addressed by
photoluminescence excitation spectroscopy of a single quantum dot. We also
investigate the implications for cavity QED, i.e. a coupled quantum dot-cavity
system, and demonstrate that the phonon scattering may be strongly quenched.
The quenching is explained by a balancing between the deformation potential
interaction strengths and the carrier confinement and depends on the quantum
dot shape. Numerical examples suggest a route towards engineering the phonon
scattering.Comment: 5 pages, 5 figures, submitted for peer review, comments are welcom
Analysis of optical properties of strained semiconductor quantum dots for electromagnetically induced transparency
Using multiband k*p theory we study the size and geometry dependence on the
slow light properties of conical semiconductor quantum dots. We find the V-type
scheme for electromagnetically induced transparency (EIT) to be most favorable,
and identify an optimal height and size for efficient EIT operation. In case of
the ladder scheme, the existence of additional dipole allowed intraband
transitions along with an almost equidistant energy level spacing adds
additional decay pathways, which significantly impairs the EIT effect. We
further study the influence of strain and band mixing comparing four different
k*p band structure models. In addition to the separation of the heavy and light
holes due to the biaxial strain component, we observe a general reduction in
the transition strengths due to energy crossings in the valence bands caused by
strain and band mixing effects. We furthermore find a non-trivial quantum dot
size dependence of the dipole moments directly related to the biaxial strain
component. Due to the separation of the heavy and light holes the optical
transition strengths between the lower conduction and upper most valence-band
states computed using one-band model and eight-band model show general
qualitative agreement, with exceptions relevant for EIT operation.Comment: 9 pages, 12 figure
Triplet Production by Linearly Polarized Photons
The process of electron-positron pair production by linearly polarized
photons is used as a polarimeter to perform mobile measurement of linear photon
polarization. In the limit of high photon energies, omega, the distributions of
the recoil-electron momentum and azimuthal angle do not depend on the photon
energy in the laboratory frame. We calculate the power corrections of order
m/omega to the above distributions and estimate the deviation from the
asymptotic result for various values of omega.Comment: LaTeX2e, 13 pages, 5 figure files (eps), submitted to Phys. Rev.
Polarized triplet production by circularly polarized photons
A process of the pair production by a circularly polarized photon in the
field of unpolarized atomic electron has been considered in the
Weizaecker-Williams approximation. The degree of longitudinal polarization of
positron and electron has been calculated. An exclusive cross-section as well
as a spectral distribution are obtained. We estimate the accuracy of our
calculations at the level of a few percent. We show the identity of the
positron polarization for considered process and for process of pair production
in the screened Coulomb field of nucleus.Comment: 9 pages, 3 picture
Nursing staff’s knowledge and attitudes towards Dementia in an Indian nursing home: A qualitative interview study
Background: Despite the increased prevalence of dementia in India, there is reported to be little awareness of the disease. This could lead to a late diagnosis, a reduced number of choices regarding future care, and misinterpretation of the symptoms or neglect. Taking into consideration that most nurses caring for older people in the future will work with people with dementia, there is concern that they may not be able to meet the needs of this group of patients unless they have the necessary knowledge and a positive attitude.
Aim: To explore the knowledge about and attitude towards dementia among nursing staff working in residential care facilities for older people in India.
Method: An explorative and descriptive qualitative design was used. Two semistructured focus group interviews were conducted with nursing staff working in 6 nursing homes in India. Qualitative content analysis was used. Ethical approval was granted by the Norwegian Social Science Data Services.
Findings: The participants highlighted the following 3 dimensions in relation to their knowledge of and attitudes toward dementia in residential care facilities in India: (1) people with dementia – a walking mystery; (2) we need to go along with them, but it is challenging; and (3) if we know, we can care for them in a better way.
Conclusion: The findings revealed a wide range of differences in attitude towards and inadequate knowledge of dementia among nursing staff. However, their overall attitudes toward people with dementia was positive.publishedVersio
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