318 research outputs found
Suicides in Psychiatric Patients: Identifying Health Care-Related Factors through Clinical Practice Reviews.
The objective of this study was to identify health care-related factors associated with death by suicide in psychiatric patients and to gain insight into clinician views on how to deal with suicidality. The study material derived from a clinician committee in a psychiatric department reviewing every outpatient and inpatient suicide in a standardized way. Reports' conclusions and corresponding plenary discussion minutes regarding 94 suicides were analyzed using inductive thematic content analysis. Health care-related factors were categorized into 4 themes: patient evaluation, patient management, clinician training, and involvement of relevant non-clinical partners. Clinician views on the themes were expressed through statements (i) promoting or restricting an aspect of care (here called recommendations), which mainly followed existing guidelines and were consensual and (ii) without precise indication (here called comments), which departed from mainstream opinions or addressed topics not covered by existing policy. Involvement of non-clinical partners emerged as a new key issue for suicide prevention in psychiatric departments and should be openly discussed with patients. Clinicians preferred balanced conclusions when they reviewed suicide cases
Engineering the spatial confinement of exciton-polaritons in semiconductors
We demonstrate the spatial confinement of electronic excitations in a solid
state system, within novel artificial structures that can be designed having
arbitrary dimensionality and shape. The excitations under study are
exciton-polaritons in a planar semiconductor microcavity. They are confined
within a micron-sized region through lateral trapping of their photon
component. Striking signatures of confined states of lower and upper polaritons
are found in angle-resolved light emission spectra, where a discrete energy
spectrum and broad angular patterns are present. A theoretical model supports
unambiguously our observations
Cancellation of probe effects in measurements of spin polarized momentum density by electron positron annihilation
Measurements of the two dimensional angular correlation of the
electron-positron annihilation radiation have been done in the past to detect
the momentum spin density and the Fermi surface. We point out that the momentum
spin density and the Fermi Surface of ferromagnetic metals can be revealed
within great detail owing to the large cancellation of the electron-positron
matrix elements which in paramagnetic multiatomic systems plague the
interpretation of the experiments. We prove our conjecture by calculating the
momentum spin density and the Fermi surface of the half metal CrO2, who has
received large attention due to its possible applications as spintronics
material
Laser-driven plasma waves in capillary tubes
The excitation of plasma waves over a length of up to 8 centimeters is, for
the first time, demon- strated using laser guiding of intense laser pulses
through hydrogen filled glass capillary tubes. The plasma waves are diagnosed
by spectral analysis of the transmitted laser radiation. The dependence of the
spectral redshift, measured as a function of filling pressure, capillary tube
length and incident laser energy, is in excellent agreement with simulation
results. The longitudinal accelerating field inferred from the simulations is
in the range 1 -10 GV/m
Experimental evidence for fast cluster formation of chain oxygen vacancies in YBa2Cu3O7-d being at the origin of the fishtail anomaly
We report on three different and complementary measurements, namely
magnetisation measurements, positron annihilation spectroscopy and NMR
measurements, which give evidence that the formation of oxygen vacancy clusters
is on the origin of the fishtail anomaly in YBa2Cu3O7-d. While in the case of
YBa2Cu3O7.0 the anomaly is intrinsically absent, it can be suppressed in the
optimally doped state where vacancies are present. We therefore conclude that
the single vacancies or point defects can not be responsible for this anomaly
but that clusters of oxygen vacancies are on its origin.Comment: 10 pages, 4 figures, submitted to PR
Scanning Tunneling Microscope-Induced Luminescence Spectroscopy on Semiconductor Heterostructures
Scanning tunneling microscope (STM)-induced luminescence is explored as a technique for the characterization of semiconductor quantum wells and quantum wire heterostructures. By injecting minority carriers into the cleaved cross section of these structures, luminescence excitation on a nanometer scale is demonstrated. Using spectrally resolved STM-induced luminescence for the tip placed at various positions across the cleaved heterostructure, it is possible to obtain local spectroscopic information on closely spaced quantum structures
Frieze Patterns of Integers
The famous theorem of Conway and Coxeter on frieze patterns gave a geometric
interpretation to integral friezes via triangulations of polygons. In this
article, we review this result and show some of the development it has led to.
The last decade has seen a lot of activities on friezes. One reason behind this
is the connection to cluster combinatorics.Comment: 9 pages, 6 figure
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