Biomedical subjects

M Hofstadter

Publications and source records attributed to M Hofstadter.

3 recordsLinked to original sources

PubMed2002

Ultra-relativistic electrons in Jupiter's radiation belts.

Ground-based observations have shown that Jupiter is a two-component source of microwave radio emission: thermal atmospheric emission and synchrotron emission from energetic electrons spiralling in Jupiter's magnetic field. Later in situ measurements confirmed the existence of Jupiter's high-energy electron-radiation belts, with evidence for electrons at energies up to 20[?]MeV. Although most radiation belt models predict electrons at higher energies, adiabatic diffusion theory can account only for energies up to around 20[?]MeV. Unambiguous evidence for more energetic electrons is lacking. Here we report observations of 13.8[?]GHz synchrotron emission that confirm the presence of electrons with energies up to 50[?]MeV; the data were collected during the Cassini fly-by of Jupiter. These energetic electrons may be repeatedly accelerated through an interaction with plasma waves, which can transfer energy into the electrons. Preliminary comparison of our data with model results suggests that electrons with energies of less than 20[?]MeV are more numerous than previously believed.

Journal Article↗

PubMed1997

Parental desire for perioperative information and informed consent: a two-phase study.

The purpose of this investigation was to identify the perioperative anesthetic information parents want from the anesthesiologist, and to determine whether the provision of detailed anesthetic risk information is associated with increased parental anxiety. The investigation consisted of a cross-sectional study followed by a randomized controlled trial. In Phase 1, baseline and situational anxiety, coping strategy, and temperament were obtained from parents of children undergoing surgery (n = 334). A questionnaire examining the desire for perioperative information was administered to all parents. In Phase 2, 47 parents were randomly assigned to receive either routine anesthetic risk information (control) or detailed anesthetic risk information (intervention). The effect of the intervention on parental anxiety was assessed over four time points: prior to the intervention, immediately after the intervention, day of surgery in the holding area, and at separation to the operating room. For Phase 1, the majority of parents (> 95%) preferred to have comprehensive information concerning their child's perioperative period, including information about all possible complications. For selected items, increased parental educational level was associated with increased desire for information (P < 0.05). For Phase 2, when the intervention group was compared with the control group, there were no significant differences in parental anxiety over the four time points [F(1,45) = 0.6, P = 0.4]. Also, the interaction between time and group assignment was not significant [F(3,135) = 1.66, P = 0.18]. We conclude that parents of children undergoing surgery desire comprehensive perioperative information. Moreover, when provided with highly detailed anesthetic risk information, the parental anxiety level did not increase.

Adaptation, Psychological↗

PubMed1996

Response modality affects human infant delayed-response performance.

Delayed response performance was assessed in 120 7-, 9-, and 11-month-old infants with correct response defined as either retrieval of a hidden object or gaze toward the location where the object was hidden. Performance improved with age, was above chance for each age group in each condition, and was more often correct with the gaze response. When direction of gaze and reach differed, direction of gaze was more likely to be correct. Infants in the reach condition were more likely to fail to reverse a previously correct response (i.e., to make the A-not-B error). Perseverative responding occurred frequently and was more likely in the reach than the gaze condition. This effect emerged primarily in the context of an incorrect response, which suggests modality-specific sensitivity to the effect of priming rather than reinforcement. Many infants showed strong side biases, and there was a tendency for more reaches to the left but gazes to the right. In a second experiment, 12 5-month-olds gazed toward the correct location more frequently than would be expected by chance but failed to reverse a previously correct response more often than older infants. These findings indicate that response modality has a significant effect on delayed-response performance.

Age Factors↗