123 research outputs found
The Effects of Prior Exposure on Face Processing in Younger and Older Adults
Older adults differ from their younger counterparts in the way they view faces. We assessed whether older adults can use past experience to mitigate these typical face-processing differences; that is, we examined whether there are age-related differences in the use of memory to support current processing. Eye movements of older and younger adults were monitored as they viewed faces that varied in the type/amount of prior exposure. Prior exposure was manipulated by including famous and novel faces, and by presenting faces up to five times. We expected that older adults may have difficulty quickly establishing new representations to aid in the processing of recently presented faces, but would be able to invoke face representations that have been stored in memory long ago to aid in the processing of famous faces. Indeed, younger adults displayed effects of recent exposure with a decrease in the total fixations to the faces and a gradual increase in the proportion of fixations to the eyes. These effects of recent exposure were largely absent in older adults. In contrast, the effect of fame, revealed by a subtle increase in fixations to the inner features of famous compared to non-famous faces, was similar for younger and older adults. Our results suggest that older adultsā current processing can benefit from lifetime experience, however the full benefit of recent experience on face processing is not realized in older adults
Transverse Magnetoresistance of GaAs/AlGaAs Heterojunctions in the Presence of Parallel Magnetic Fields
We have calculated the resistivity of a GaAs\slash AlGaAs heterojunction in
the presence of both an in--plane magnetic field and a weak perpendicular
component using a semiclassical Boltzmann transport theory. These calculations
take into account fully the distortion of the Fermi contour which is induced by
the parallel magnetic field. The scattering of electrons is assumed to be due
to remote ionized impurities. A positive magnetoresistance is found as a
function of the perpendicular component, in good qualitative agreement with
experimental observations. The main source of this effect is the strong
variation of the electronic scattering rate around the Fermi contour which is
associated with the variation in the mean distance of the electronic states
from the remote impurities. The magnitude of the positive magnetoresistance is
strongly correlated with the residual acceptor impurity density in the GaAs
layer. The carrier lifetime anisotropy also leads to an observable anisotropy
in the resistivity with respect to the angle between the current and the
direction of the in--plane magnetic field.Comment: uuencoded file containing a 26 page RevTex file and 14 postscript
figures. Submitted to Phys. Rev.
Physical Activity and Mindfulness are Associated with Lower Anxiety in Different but Complementary Ways
International Journal of Exercise Science 15(7): 1075-1084, 2022. Introduction: Anxiety is the most prevalent mental illness worldwide. Physical activity and mindfulness both reduce anxiety. The two are highly related; however, the relative association of physical activity and mindfulness on anxiety has yet to be examined. The present study aimed to evaluate the unique variance accounted for by physical activity and mindfulness on anxiety. Methods: Fifty young adults from a student population (M Ā± SD = 19 Ā± 0.2 years old; 58% female) reported their physical activity, mindfulness, and anxiety symptoms at the start of the study and reported their change in state anxiety to an acute psychological stress test, Trier Social Stress Test. Results: Mindfulness explained more of the variance associated with anxiety symptoms at baseline, whereas physical activity explained more of the variance associated with change in state anxiety in response to the acute stressor. Females had higher rates of anxiety symptoms than males suggesting that females may benefit more from mindfulness. In contrast, both males and females reacted similarly to an acute stressor suggesting that both genders may benefit from physical activity. Conclusions: Our findings suggest that physical activity and trait mindfulness may have related, but distinct impacts on anxiety levels. These results have important implications for using these lifestyle interventions to support mental health and point to personalizing interventions to help ease the burden of anxiety felt by the individual
Capacitance of Gated GaAs/AlGaAs Heterostructures Subject to In-plane Magnetic Fields
A detailed analysis of the capacitance of gated GaAs/AlGaAs heterostructures
is presented. The nonlinear dependence of the capacitance on the gate voltage
and in-plane magnetic field is discussed together with the capacitance quantum
steps connected with a population of higher 2D gas subbands. The results of
full self-consistent numerical calculations are compared to recent experimental
data.Comment: 4 pages, Revtex. 4 PostScript figures in an uuencoded compressed file
available upon request. Phys. Rev.B, in pres
In-Plane Magnetic Field Induced Anisotropy of 2D Fermi Contours and the Field Dependent Cyclotron Mass
The electronic structure of a 2D gas subjected to a tilted magnetic field,
with a strong component parallel to the GaAs/AlGaAs interface and a weak
component oriented perpendicularly, is studied theoretically. It is shown that
the parallel field component modifies the originally circular shape of a Fermi
contour while the perpendicular component drive an electron by the Lorentz
force along a Fermi line with a cyclotron frequency given by its shape. The
corresponding cyclotron effective mass is calculated self-consistently for
several concentrations of 2D carriers as a function of the in-plane magnetic
field. The possibility to detect its field-induced deviations from the zero
field value experimentally is discussed.Comment: written in LaTeX, 9 pages, 4 figures (6 pages) in 1 PS file
(compressed and uuencoded) available on request from [email protected],
SM-JU-93-
Inter-layer Hall effect in double quantum wells subject to in-plane magnetic fields
We report on a theoretical study of the transport properties of two coupled
two-dimensional electron systems subject to in-plane magnetic fields. The
charge redistribution in double wells induced by the Lorenz force in crossed
electric and magnetic fields has been studied. We have found that the
redistribution of the charge and the related inter-layer Hall effect originate
in the chirality of diamagnetic currents and give a substantial contribution to
the conductivity.Comment: 7 RevTex pages, 4 figures, appendix added and misprint in Eq. (11)
correcte
Towards Contextual Action Recognition and Target Localization with Active Allocation of Attention
Exploratory gaze movements are fundamental for gathering the most relevant information regarding the partner during social interactions. We have designed and implemented a system for dynamic attention allocation which is able to actively control gaze movements during a visual action recognition task. During the observation of a partners reaching movement, the robot is able to contextually estimate the goal position of the partner hand and the location in space of the candidate targets, while moving its gaze around with the purpose of optimizing the gathering of information relevant for the task. Experimental results on a simulated environment show that active gaze control provides a relevant advantage with respect to typical passive observation, both in term of estimation precision and of time required for action recognition. Ā© 2012 Springer-Verlag
Density of states and electron concentration of double heterojunctions subjected to an in-plane magnetic field
We calculate the electronic states of
AlGaAs/GaAs/AlGaAs double heterojunctions subjected to
a magnetic field parallel to the quasi two-dimensional electron gas. We study
the energy dispersion curves, the density of states, the electron concentration
and the distribution of the electrons in the subbands. The parallel magnetic
field induces severe changes in the density of states, which are of crucial
importance for the explanation of the magnetoconductivity in these structures.
However, to our knowledge, there is no systematic study of the density of
states under these circumstances. We attempt a contribution in this direction.
For symmetric heterostructures, the depopulation of the higher subbands, the
transition from a single to a bilayer electron system and the domination of the
bulk Landau levels in the centre the wide quantum well, as the magnetic field
is continuously increased, are presented in the ``energy dispersion picture''
as well as in the ``electron concentration picture'' and in the ``density of
states picture''.Comment: J. Phys.: Condens. Matter 11 No 26 (5 July 1999) 5131-5141 Figures
(three) embedde
Monitoring lower limb biomechanical asymmetry and psychological measures in athletic populations - A scoping review
Background: Lower limb biomechanics, including asymmetry, are frequently monitored to determine sport performance level and injury risk. However, contributing factors extend beyond biomechanical and asymmetry measures to include psychological, sociological, and environmental factors. Unfortunately, inadequate research has been conducted using holistic bio-psycho-social models to characterize sport performance and injury risk. Therefore, this scoping review summarized the research landscape of studies concurrently assessing measures of lower limb biomechanics, asymmetry, and introspective psychological state (e.g., pain, fatigue, perceived exertion, stress, etc.) in healthy, competitive athletes. Methods: A systematic search of Medline, Embase, CINAHL, SPORT Discus, and Web of Science Core Collections was designed and conducted in accordance with PRISMA guidelines. 51 articles were included in this review. Results: Significant relationships between biomechanics (k = 22 studies) or asymmetry (k = 20 studies) and introspective state were found. Increased self-reported pain was associated with decreased range of motion, strength, and increased lower limb asymmetry. Higher ratings of perceived exertion were related to increased lower limb asymmetry, self-reported muscle soreness, and worse jump performance. Few studies (k = 4) monitored athletes longitudinally throughout one or more competitive season(s). Conclusion: This review highlights the need for concurrent analysis of introspective, psychological state, and biomechanical asymmetry measures along with longitudinal research to understand the contributing factors to sport performance and injury risk from bio-psycho-social modeling. In doing so, this framework of bio-psycho-social preventive and prognostic patient-centered practices may provide an actionable means of optimizing health, well-being, and sport performance in competitive athletes
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