54 research outputs found
Associative Learning from Verbal Action-Effect Instructions: A Replication and Investigation of Underlying Mechanisms
According to the ideomotor principle, repeated experience with an action and its
perceivable consequences (effects) establish action-effect associations. Research
on verbal instructions indicates that such associations are also acquired from
verbal information. In the present experiment (N = 651), first, we aimed to replicate
unintentional response-priming effects from verbal action-effect instructions (direct
replication; Condition 1). Second, we investigated the involvement of perceptual
processes in the verbally induced response-priming effect by perceptually presenting
(Condition 1) versus not presenting (Condition 2) the color that was subsequently
named as an effect in the instructions. Third, we tested a saliency-based explanation
of the verbally induced response-priming effect by highlighting all components (action
and effect) without an association between them (Condition 3). Overall, we found the
predicted response-priming effect following verbal action-effect instructions (overall
conditions and in the replication Condition 1). Condition 2, which did not include
perceptual information in the instructions, still showed a significant response-priming
effect but was descriptively weaker compared to the effect of the replication Condition
1. Condition 3, which merely highlighted the action and effect component without
endorsing an association, did not show a significant effect. In sum, our study provides
further solid evidence that verbal instructions lead to unintentional response-priming
effects. Other conclusions must be considered preliminary: The between-condition
comparisons were descriptively in the predicted direction—perceptual aspects are
relevant, and a saliency-based account can be excluded—but the differences in
accuracy between conditions were not statistically significant
Экспериментальное исследование динамики фрикционных процессов при трении латуни Л63 с ультрамелкозернистой структурой
В работе рассматривается экспериментальное исследование динамики фрикционных процессов при трении объемных ультрамелкозернистых материалов. В качестве модельных образцов использовалась латунь Л63 с крупнокристаллической и ультрамелкозернистой структурой, сформированной методом равноканального углового прессования. В процессе сухого трения скольжения осуществлялась регистрация сигналов виброускорений и акустической эмиссии. Анализ коротких сигналов с применением преобразований Фурье позволил установить характерные параметры сигналов, полученных при трении крупнокристаллических и ультрамелкозернистых материалов
Low-energy Compton scattering on the nucleon and sum rules
The Gerasimov-Drell-Hearn and Baldin-Lapidus sum rules are evaluated in the
dressed K-matrix model for photon-induced reactions on the nucleon. For the
first time the sum of the electric and magnetic polarisabilities
and the forward spin polarisability are explicitly calculated in two
alternative ways -- from the sum rules and from the low-energy expansion of the
real Compton scattering amplitude -- within the {\em same} framework. The two
methods yield compatible values for but differ somewhat for
. Consistency between the two ways of determining the
polarisabilities is a measure of the extent to which basic symmetries of the
model are obeyed.Comment: 9 pages, 4 figures, using REVTeX. More concise version, results
unchanged. To appear in Phys. Rev.
Compton scattering in a unitary approach with causality constraints
Pion-loop corrections for Compton scattering are calculated in a novel
approach based on the use of dispersion relations in a formalism obeying
unitarity. The basic framework is presented, including an application to
Compton scattering. In the approach the effects of the non-pole contribution
arising from pion dressing are expressed in terms of (half-off-shell) form
factors and the nucleon self-energy. These quantities are constructed through
the application of dispersion integrals to the pole contribution of loop
diagrams, the same as those included in the calculation of the amplitudes
through a K-matrix formalism. The prescription of minimal substitution is used
to restore gauge invariance. The resulting relativistic-covariant model
combines constraints from unitarity, causality, and crossing symmetry.Comment: 25 pages, 9 ps-figure
Typhoid fever among children, Ghana.
Typhoid fever
(TF) remains a problem of concern in
many low-income countries. Salmonella enterica serovar Typhi causes
≈22,000,000 symptomatic infections
and 220,000 fatalities worldwide annually (1). However, the effect and
incidence of TF in many parts of subSaharan Africa are largely unknown
because diagnostic laboratories are
lacking and fatal TF is frequently attributed to malaria (2,3). In Ghana,
TF ranks among the leading 20 causes
of outpatient illness, accounting for
0.92% of hospital admissions (4).
We conducted our study at the
rural Agogo Presbyterian Hospital
in the Ashanti Region of Ghana. The
percentage of residents of 99 villages
and household clusters of buildings
(population size 18–13,559 persons,
median 277 persons) with access to
the study hospital was assessed in a
healthcare utilization survey. A proportional-to-size number of children
were randomly selected in each village, and a standardized interview
was conducted. TF incidences were
calculated for September 2007–November 2008 (Table). A bacteriology
laboratory with BACTEC 9050 automated blood culture system (Becton
Dickinson, Sparks, MD, USA) was
established in the study hospital and
run to assess the number of admissions with TF, the incidence of TF in
the adjoining community and S. enterica ser. Typhi resistance to a panel
of antimicrobial drugs
Electromagnetic Polarizabilities of Nucleons bound in Ca, O and He
Differential cross sections for elastic scattering of photons have been
measured for Ca at energies of 58 and 74 MeV and for O and He
at 61 MeV, in the angular range from 45 to 150. Evidence is obtained
that there are no significant in-medium modifications of the electromagnetic
polarizabilities except for those originating from meson exchange currents.Comment: 20 pages including 5 Figure
Compton scattering on the nucleon at intermediate energies and polarizabilities in a microscopic model
A microscopic calculation of Compton scattering on the nucleon is presented
which encompasses the lowest energies -- yielding nucleon polarizabilities --
and extends to energies of the order of 600 MeV. We have used the covariant
"Dressed K-Matrix Model" obeying the symmetry properties which are appropriate
in the different energy regimes. In particular, crossing symmetry, gauge
invariance and unitarity are satisfied. The extent of violation of analyticity
(causality) is used as an expansion parameter.Comment: 35 pages, 15 figures, using REVTeX. Modified version to be published
in Phys. Rev. C, more extensive comparison with data for Compton scattering,
all results unchange
Dispersion relations in real and virtual Compton scattering
A unified presentation is given on the use of dispersion relations in the
real and virtual Compton scattering processes off the nucleon. The way in which
dispersion relations for Compton scattering amplitudes establish connections
between low energy nucleon structure quantities, such as polarizabilities or
anomalous magnetic moments, and the nucleon excitation spectrum is reviewed. We
discuss various sum rules for forward real and virtual Compton scattering, such
as the Gerasimov-Drell-Hearn sum rule and its generalizations, the
Burkhardt-Cottingham sum rule, as well as sum rules for forward nucleon
polarizabilities, and review their experimental status. Subsequently, we
address the general case of real Compton scattering (RCS). Various types of
dispersion relations for RCS are presented as tools for extracting nucleon
polarizabilities from the RCS data. The information on nucleon polarizabilities
gained in this way is reviewed and the nucleon structure information encoded in
these quantities is discussed. The dispersion relation formalism is then
extended to virtual Compton scattering (VCS). The information on generalized
nucleon polarizabilities extracted from recent VCS experiments is described,
along with its interpretation in nucleon structure models. As a summary, the
physics content of the existing data is discussed and some perspectives for
future theoretical and experimental activities in this field are presented.Comment: 120 pages, 42 figures, to appear in Phys. Re
Compton Scattering by Nuclei
The concept of Compton scattering by even-even nuclei from giant-resonance to
nucleon-resonance energies and the status of experimental and theoretical
researches in this field are outlined. Nuclear Compton scattering in the
giant-resonance energy-region provides information on the dynamical properties
of the in-medium mass of the nucleon. The electromagnetic polarizabilities of
the nucleon in the nuclear medium can be extracted from nuclear Compton
scattering data obtained in the quasi-deuteron energy-region. Recent results
are presented for two-body effects due to the mesonic seagull amplitude and due
to the excitation of nucleon internal degrees of freedom accompanied by meson
exchanges. Due to these studies the in-medium electromagnetic polarizabilities
are by now well understood, whereas the understanding of nuclear Compton
scattering in the Delta-resonance range is only at the beginning.
Phenomenological methods how to include retardation effects in the scattering
amplitude are discussed and compared with model predictions.Comment: 146 pages, 37 figures, submitted to Phys. Report
Vector meson production and nucleon resonance analysis in a coupled-channel approach for energies m_N < sqrt(s) < 2 GeV II: photon-induced results
We present a nucleon resonance analysis by simultaneously considering all
pion- and photon-induced experimental data on the final states gamma N, pi N, 2
pi N, eta N, K Lambda, K Sigma, and omega N for energies from the nucleon mass
up to sqrt(s) = 2 GeV. In this analysis we find strong evidence for the
resonances P_{31}(1750), P_{13}(1900), P_{33}(1920), and D_{13}(1950). The
omega N production mechanism is dominated by large P_{11}(1710) and
P_{13}(1900) contributions. In this second part we present the results on the
photoproduction reactions and the electromagnetic properties of the resonances.
The inclusion of all important final states up to sqrt(s) = 2 GeV allows for
estimates on the importance of the individual states for the GDH sum rule.Comment: 41 pages, 26 figures, discussion extended, typos corrected,
references updated, to appear in Phys. Rev.
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