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Biomedical subjects

M E Ware

Publications and source records attributed to M E Ware.

7 recordsLinked to original sources
PubMed2006

Optical signatures of coupled quantum dots.

An asymmetric pair of coupled InAs quantum dots is tuned into resonance by applying an electric field so that a single hole forms a coherent molecular wave function. The optical spectrum shows a rich pattern of level anticrossings and crossings that can be understood as a superposition of charge and spin configurations of the two dots. Coulomb interactions shift the molecular resonance of the optically excited state (charged exciton) with respect to the ground state (single charge), enabling light-induced coupling of the quantum dots. This result demonstrates the possibility of optically coupling quantum dots for application in quantum information processing.

Journal Article↗
PubMed2005

Polarized fine structure in the photoluminescence excitation spectrum of a negatively charged quantum dot.

We report polarized photoluminescence excitation spectroscopy of the negative trion in single charge-tunable quantum dots. The spectrum exhibits a p-shell resonance with polarized fine structure arising from the direct excitation of the electron spin triplet states. The energy splitting arises from the axially symmetric electron-hole exchange interaction. The magnitude and sign of the polarization are understood from the spin character of the triplet states and a small amount of quantum dot asymmetry, which mixes the wave functions through asymmetric e-e and e-h exchange interactions.

Journal Article↗
PubMed2005

Optical pumping of the electronic and nuclear spin of single charge-tunable quantum dots.

We present a comprehensive examination of optical pumping of spins in individual GaAs quantum dots as we change the net charge from positive to neutral to negative with a charge-tunable heterostructure. Negative photoluminescence polarization memory is enhanced by optical pumping of ground state electron spins, which we prove with the first measurements of the Hanle effect on an individual quantum dot. We use the Overhauser effect in a high longitudinal magnetic field to demonstrate efficient optical pumping of nuclear spins for all three charge states of the quantum dot.

Journal Article↗
PubMed2004

Suppression of Dyakonov-Perel spin relaxation in high-mobility n-GaAs.

We report a large and unexpected suppression of the free electron spin-relaxation in lightly doped n-GaAs bulk crystals. The spin-relaxation rate shows a weak mobility dependence and saturates at a level 30 times less than that predicted by the Dyakonov-Perel theory. The dynamics of the spin-orbit field differs substantially from the usual scheme: although all the experimental data can be self-consistently interpreted as a precessional spin-relaxation induced by a random spin-orbit field, the correlation time of this random field, surprisingly, is much shorter than, and is independent of, the momentum relaxation time determined from transport measurements.

Journal Article↗
PubMed1990

Parents' and health professionals' perceptions concerning parental stress during a child's hospitalization.

This study compared mothers', fathers', nurses', and physicians' perceptions of parents' reactions to stressful stimuli when their children were hospitalized. Thirty-six mothers, 14 fathers, 27 nurses, and 23 physicians rated 36 stressful stimuli on an inventory the investigators developed. Analysis of Variance and subsequent multiple comparison tests disclosed numerous differences between parents and health care professionals and between mothers and fathers on the Parental Uncertainty, Annoyance, Child Discomfort, and Negative Emotional States Scales. Further analyses of ratings on individual items from the scales revealed the bases of the differences. Implications for health professionals and directions for further research are discussed.

Child↗
PubMed1980

The effectiveness of anchor characteristics on perceptual discrimination.

Four experiments using stimuli which varied in size or texture investigated whether shifts in discrimination occurred when anchors and series stimuli were integral or nonintegral A total of 120 male and female college students judged series stimuli with respect to size. Anchors differed from the series stimuli in size or texture. The participants always observed the anchors visually. The E presented series stimuli either to the visual (intramodal) or haptic (crossmodal) sense. Analysis of variance revealed significant shifts in perceptual judgment for anchors presented both intra- and crossmodally but only when anchors and series stimuli dimensions were integral. Adaptation-level theory predicted significant shifts in judgment and properties associated with the dimensional structure of stimuli accounted for the limits of anchor effectiveness.

Discrimination Learning↗