746 research outputs found
Does Perceptual Learning Suffer from Retrograde Interference?
In motor learning, training a task B can disrupt improvements of performance of a previously learned task A, indicating that learning needs consolidation. An influential study suggested that this is the case also for visual perceptual learning [1]. Using the same paradigm, we failed to reproduce these results. Further experiments with bisection stimuli also showed no retrograde disruption from task B on task A. Hence, for the tasks tested here, perceptual learning does not suffer from retrograde interference
Description of superdeformed nuclei in the interacting boson model
The interacting boson model is extended to describe the spectroscopy of
superdeformed bands. Microscopic structure of the model in the second minimum
is discussed and superdeformed bosons are introduced as the new building
blocks. Solutions of a quadrupole Hamiltonian are implemented through the
expansion method. Effects of the quadrupole parameters on dynamic moment of
inertia and electric quadrupole transition rates are discussed and the results
are used in a description of superdeformed bands in the Hg-Pb and Gd-Dy
regions.Comment: 18 pages revtex, 9 figures available upon reques
Calculation of the photoionization with de-excitation cross sections of He and helium-like ions
We discuss the results of the calculation of the photoionization with
de-excitation of excited He and helium-like ions Li and B at high
but non-relativistic photon energies . Several lower and
states are considered. We present and analyze the ratios
of the cross sections of photoionization with de-excitation,
, and of the photo-ionization with excitation,
. The dependence of on the excitation
of the target object and the charge of its nucleus is presented. Apart to
theoretical interest, results obtained can be verified using such long living
excited state as of He.Comment: 10 pages, 6 table
Quasiclassical double photoionization from the 2^{1,3}S excited states of helium including shakeoff
We account for the different symmetries of the 2^{1,3}S helium excited states
in a quasiclassical description of the knockout mechanism augmented by a
quantum shakeoff contribution. We are thus able to formulate the separate
contribution of the knockout and shakeoff mechanisms for double photoionization
for any excess energy from the 2^{1,3}S states. Photoionization ratios and
singly differential cross sections calculated for the 2^{1,3}S excited states
of helium are found to be in very good agreement with recent theoretical
results.Comment: 9 pages, 5 figure
Mixed ab initio quantum mechanical and Monte Carlo calculations of secondary emission from SiO2 nanoclusters
A mixed quantum mechanical and Monte Carlo method for calculating Auger
spectra from nanoclusters is presented. The approach, based on a cluster
method, consists of two steps. Ab initio quantum mechanical calculations are
first performed to obtain accurate energy and probability distributions of the
generated Auger electrons. In a second step, using the calculated line shape as
electron source, the Monte Carlo method is used to simulate the effect of
inelastic losses on the original Auger line shape. The resulting spectrum can
be directly compared to 'as-acquired' experimental spectra, thus avoiding
background subtraction or deconvolution procedures. As a case study, the O K-LL
spectrum from solid SiO2 is considered. Spectra computed before or after the
electron has traveled through the solid, i.e., unaffected or affected by
extrinsic energy losses, are compared to the pertinent experimental spectra
measured within our group. Both transition energies and relative intensities
are well reproduced.Comment: 9 pageg, 5 figure
Local Spectral Density for a Periodically Driven System of Coupled Quantum States with Strong Imperfection in Unperturbed Energies
A random matrix theory approach is applied in order to analyze the
localization properties of local spectral density for a generic system of
coupled quantum states with strong static imperfection in the unperturbed
energy levels. The system is excited by an external periodic field, the
temporal profile of which is close to monochromatic one. The shape of local
spectral density is shown to be well described by the contour obtained from a
relevant model of periodically driven two-states system with irreversible
losses to an external thermal bath. The shape width and the inverse
participation ratio are determined as functions both of the Rabi frequency and
of parameters specifying the localization effect for our system in the absence
of external field.Comment: 6 pages, 5 figures, submitted to Optics and Spectroscop
An affordable methodology for quantifying waterborne microplastics - an emerging contaminant in inland-waters
The occurrence of microplastics in marine habitats is well documented and of growing concern. The presence of these small (<5 mm) pieces of plastic is less well recorded in inland water systems. In this paper, we determine a cost-efficient and straightforward method for the collection and identification of microplastics in UK inland waters. We found pieces of microplastic from all sample sites ranging from over 1000 L-1 in the River Tame, to 2.4 L-1 in Loch Lomond. The presence of microplastics in all waters tested suggest it should now be classed as an emergent contaminant, with routine monitoring required
TLR2 expression is increased in rosacea and stimulates enhanced serine protease production by keratinocytes.
A diverse environment challenges skin to maintain temperature, hydration, and electrolyte balance while also maintaining normal immunological function. Rosacea is a common skin disease that manifests unique inflammatory responses to normal environmental stimuli. We hypothesized that abnormal function of innate immune pattern recognition could explain the enhanced sensitivity of patients with rosacea, and observed that the epidermis of patients with rosacea expressed higher amounts of Toll-like receptor 2 (TLR2) than normal patients. Increased expression of TLR2 was not seen in other inflammatory skin disorders such as atopic dermatitis or psoriasis. Overexpression of TLR2 on keratinocytes, treatment with TLR2 ligands, and analysis of TLR2-deficient mice resulted in a calcium-dependent release of kallikrein 5 from keratinocytes, a critical protease involved in the pathogenesis of rosacea. These observations show that abnormal TLR2 function may explain enhanced inflammatory responses to environmental stimuli and can act as a critical element in the pathogenesis of rosacea
Cluster Interpretation of Properties of Alternating Parity Bands in Heavy Nuclei
The properties of the states of the alternating parity bands in actinides,
Ba, Ce and Nd isotopes are analyzed within a cluster model. The model is based
on the assumption that cluster type shapes are produced by the collective
motion of the nuclear system in the mass asymmetry coordinate. The calculated
spin dependences of the parity splitting and of the electric multipole
transition moments are in agreement with the experimental data.Comment: 29 pages, 10 figure
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