13,294 research outputs found
Pflanzenvergiftungen â psychiatrische Aspekte
Zusammenfassung: Seit der Antike sind Pflanzenvergiftungen dokumentiert, trotzdem werden Intoxikationen mit pflanzlichen Giften im psychiatrischen Schrifttum wenig beachtet, und die Gefahr durch Giftpflanzen wird gemeinhin verkannt. In diesem Artikel wird diese Problematik erörtert. Es werden weiterhin entsprechende Empfehlungen zur Vermeidung von Pflanzenvergiftungen und zum allgemeinen Umgang mit deren Folgen gegebe
Exciton states in monolayer MoSe2: impact on interband transitions
We combine linear and non-linear optical spectroscopy at 4K with ab initio
calculations to study the electronic bandstructure of MoSe2 monolayers. In
1-photon photoluminescence excitation (PLE) and reflectivity we measure a
separation between the A- and B-exciton emission of 220 meV. In 2-photon PLE we
detect for the A- and B-exciton the 2p state 180meV above the respective 1s
state. In second harmonic generation (SHG) spectroscopy we record an
enhancement by more than 2 orders of magnitude of the SHG signal at resonances
of the charged exciton and the 1s and 2p neutral A- and B-exciton. Our
post-Density Functional Theory calculations show in the conduction band along
the direction a local minimum that is energetically and in k-space
close to the global minimum at the K-point. This has a potentially strong
impact on the polarization and energy of the excitonic states that govern the
interband transitions and marks an important difference to MoS2 and WSe2
monolayers.Comment: 8 pages, 3 figure
Towards the Perfect X-ray Beam Splitter
X-ray free-electron lasers (FEL) deliver ultrabright X-ray pulses, but not
the sequences of phase-coherent pulses required for time-domain interferometry
and control of quantum states. For conventional split-and-delay schemes to
produce such sequences the challenge stems from extreme stability requirements
when splitting Angstrom wavelength beams where tiniest path length differences
introduce phase jitter. We describe an FEL mode based on selective electron
bunch degradation and transverse beam shaping in the accelerator, combined with
a self-seeded photon emission scheme. Instead of splitting the photon pulses
after their generation by the FEL, we split the electron bunch in the
accelerator, prior to photon generation, to obtain phase-locked X-ray pulses
with sub-femtosecond duration. Time-domain interferometry becomes possible,
enabling the concomitant program of classical and quantum optics experiments
with X-rays. The scheme leads to new scientific benefits of cutting-edge FELs
with attosecond and/or high-repetition rate capabilities, ranging from the
X-ray analog of Fourier transform infrared spectroscopy to damage-free
measurements
Gravitational potential of a homogeneous circular torus: new approach
The integral expression for gravitational potential of a homogeneous circular
torus composed of infinitely thin rings is obtained. Approximate expressions
for torus potential in the outer and inner regions are found. In the outer
region a torus potential is shown to be approximately equal to that of an
infinitely thin ring of the same mass; it is valid up to the surface of the
torus. It is shown in a first approximation, that the inner potential of the
torus (inside a torus body) is a quadratic function of coordinates. The method
of sewing together the inner and outer potentials is proposed. This method
provided a continuous approximate solution for the potential and its
derivatives, working throughout the region.Comment: 10 pages, 9 figures, 1 table; some misprints in formulae were
correcte
Compliance with hygiene practices among healthcare workers in the intensive care unit
Background. Intensive care unit (ICU)-related healthcare-associated infections (HCAIs) are two to three times higher in lower-income countries than in higher-income ones. Hand cleansing and other hygiene measures have been documented as one of the most effective measures in combating the transmission of HCAIs. There is a paucity of data pertaining to hygiene practices in the ICU in developing countries.Objectives. To determine compliance with hygiene practices among healthcare workers in a tertiary hospital ICU.Methods. Hygiene practices of healthcare workers in a tertiary academic hospital ICU in Johannesburg, South Africa, were discreetly observed over an 8-week period. Compliance with hand cleansing and other hygiene practices was documented and analysed. Retrospective consent was obtained, and subject confidentiality was maintained. Results. A total of 745 hygiene opportunities were observed. Of the 156 opportunities where handwashing with soap and water was indicated (20.9%), compliance was noted in 89 cases (57.1%), while an alcohol-based hand rub was inappropriately used in 34 cases (21.8%) and no hand hygiene was performed in the remaining 33 cases (21.1%). Of the 589 opportunities where an alcohol-based hand-rub was indicated, it was used in 312 cases (53.0%). Compliance with the donning of disposable surgical gloves, disposable plastic aprons and being âbare below the elbowsâ was noted in 114 (90.6%), 108 (71.1%) and 355 (47.7%) opportunities, respectively, where these were indicated.Conclusions. Overall compliance with hygiene measures among healthcare workers in the ICU was suboptimal in this study, but in keeping with general international trends. Regular retraining of staff, frequent reminders, peer oversight and regular audits may improve compliance
Van der Waals forces in density functional theory: perturbational long-range electron interaction corrections
Long-range exchange and correlation effects, responsible for the failure of
currently used approximate density functionals in describing van der Waals
forces, are taken into account explicitly after a separation of the
electron-electron interaction in the Hamiltonian into short- and long-range
components. We propose a "range-separated hybrid" functional based on a local
density approximation for the short-range exchange-correlation energy, combined
with a long-range exact exchange energy. Long-range correlation effects are
added by a second-order perturbational treatment. The resulting scheme is
general and is particularly well-adapted to describe van der Waals complexes,
like rare gas dimers.Comment: 8 pages, 1 figure, submitted to Phys. Rev.
Morphological Abnormalities in Vitamin B6 Deficient Tarsometatarsal Chick Cartilage
The aim of this study was to test the hypothesis that deficiency of vitamin B6 would produce morphological characteristics of osteochondral lathyrism. To accomplish this goal, morphological characteristics of chick cartilage in which lathyrism was produced by two separate dietary regimens was compared to morphological changes encountered in vitamin B6 deficiency. Vitamin B6 deficiency should reduce activity of lysyloxidase needed for producing intermolecular cross-links. The question to be addressed was: would this latter deficiency impair collagen morphological features and secondarily other structures indirectly by reducing collagen molecular assembly? Failure of cross-linking of collagen in the positive controls was related to a lack of functional aldehyde cross-link intermediates which are blocked by homocysteine and aminoacetonitrile.
Day-old-male Lohmann chicks were fed adequate (6 mg/kg) or vitamin B6-deficient diets. Cross-link defects were induced by homocysteine-rich diets (0.6% w/w) or a diet containing aminoacetonitrile (0.1% w/w). Animals were sacrificed at 6 weeks of age and Ossa tarsalia articular cartilage specimens, as well as the proximal end of tarsometatarsus were dissected from the tibial metatarsal joint, a major weight-bearing site. Light microscopic observations revealed reduction of subarticular trabecular bone formation, concurrent with overexpansion of the hypertrophic cell zone. Ultrastructural electron microscopy observations of articular fibro-cartilage indicated significant thickening of collagen fibers in vitamin B6 deficient birds, as well as the positive controls in comparison to that of cage-matched control birds. It was concluded that vitamin B6 deficient cross-linking may be responsible for the observed delay in bone development and aforementioned cartilage histological alterations
Correlation between the Extraordinary Hall Effect and Resistivity
We study the contribution of different types of scattering sources to the
extraordinary Hall effect. Scattering by magnetic nano-particles embedded in
normal-metal matrix, insulating impurities in magnetic matrix, surface
scattering and temperature dependent scattering are experimentally tested. Our
new data, as well as previously published results on a variety of materials,
are fairly interpreted by a simple modification of the skew scattering model
A note on the topological order of noncommutative Hall fluids
We evaluate the ground state degeneracy of noncommutative Chern-Simons models
on the two-torus, a quantity that is interpreted as the "topological order" of
associated phases of Hall fluids. We define the noncommutative theory via
T-duality from an ordinary Chern-Simons model with non-abelian 't Hooft
magnetic fluxes. Motivated by this T-duality, we propose a discrete family of
noncommutative, non-abelian fluid models, arising as a natural generalization
of the standard noncommutative Chern-Simons effective models. We compute the
topological order for these universality classes, and comment on their possible
microscopic interpretation.Comment: 14 page
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