The Effect of Motivational General-Mastery Imagery on Reaction Time Performance and Heart Rate

Research suggests that imagery can reduce reaction time (Alikhani et al., 2001; Grouios, 1992; Hanshaw & Sukal, 2016; Iftikhar et al., 2018; Shanks & Cameron, 2000). Previous studies examining the imagery and reaction time relationship have almost exclusively focused on motor imagery. Additionally, a recent study by McNeil and colleagues (2019) concluded that imagery training improved decision time variables, but not overall reactive agility. Individuals may not be able to generate unpredictable stimuli during imagery. The purpose of this study was to examine the effects of motivational general-mastery (MG-M) imagery on reaction time and heart rate. Reaction time was measured using the Dynavision D2 visuomotor training device. It was hypothesized that the use of an MG-M imagery intervention will significantly increase reaction time and the number of hits during testing, and participants in the MG-M imagery group would have a lower heart rate range from beginning to end of test. A within-subjects and between-subjects pre-posttreatment design was implemented. Participants were 9 NCAA Division I student-athletes. The effectiveness of the imagery intervention on reaction time, number of hits, and heart rate range was assessed using nonparametric Wilcoxon-Signed rank tests and Mann-Whitney U tests. Results demonstrated that there was no statistically significant effect observed for reaction time, number of hits, or heart rate. Results suggest that MG-M imagery does not allow participants to react quicker to unpredictable stimuli, as participants could not generate unpredictable stimuli during imagery

Comparative Microbial Dynamics in Crassostrea virginica and Crassostrea ariakensis

Considerations to introduce the Suminoe or Asian oyster Crassostrea ariakensis along the East Coast have raised many questions regarding ecology, economics, and human health. To date, research has focused primarily on the ecological and socioeconomic implications of this initiative, yet few studies have assessed its potential impact on public health. Our work compares the rates of bioaccumulation, depuration and post harvest decay of indicator organisms (such as E. coli) and Vibrio sp. between Crassostrea virginica and Crassostrea ariakensis in the laboratory. Preliminary results suggest that the rates of bioaccumulation of E. coli in Crassostrea ariakensis were significantly lower than those for Crassostrea virginica, depuration of E. coli was variable between the two species, and Crassostrea ariakensis post harvest decay rates of Vibrio sp. were significantly lower than Crassostrea virginica. This research provides coastal managers with insight into the response of Crassostrea ariakensis to bacteria, an important consideration for determining appropriate management strategies for this species. Further field-based studies will be necessary to elucidate the mechanisms responsible for the differences in rates of bioaccumulation and depuration. (PDF contains 40 pages

Surface-Barrier Effects in the Microwave Second-Harmonic Response of Superconductors in the Mixed State

We report on transient effects in the microwave second-order response of different type of superconductors in the mixed state. The samples have contemporarily been exposed to a dc magnetic field, varying with a constant rate of 60 Oe/s, and a pulsed microwave magnetic field. The time evolution of the signal radiated at the second-harmonic frequency of the driving field has been measured for about 500 s from the instant in which the dc-field sweep has been stopped, with sampling time of about 0.3 s. We show that the second-harmonic signal exhibits two relaxation regimes; an initial exponential decay, which endures roughly 10 s, and a logarithmic decay in the time scale of minutes. Evidence is given that the decay in the time scale of minutes is ruled by magnetic relaxation over the surface barrier.Comment: 6 pages, 6 embedded figure

Normalization factors for magnetic relaxation of small particle systems in non-zero magnetic field

We critically discuss relaxation experiments in magnetic systems that can be characterized in terms of an energy barrier distribution, showing that proper normalization of the relaxation data is needed whenever curves corresponding to different temperatures are to be compared. We show how these normalization factors can be obtained from experimental data by using the $T \ln(t/\tau_0)$ scaling method without making any assumptions about the nature of the energy barrier distribution. The validity of the procedure is tested using a ferrofluid of Fe_3O_4 particles.Comment: 5 pages, 6 eps figures added in April 22, to be published in Phys. Rev. B 55 (1 April 1997

The Solar Twin Planet Search IV. The Sun as a typical rotator and evidence for a new rotational braking law for Sun-like stars

Context. It is still unclear how common the Sun is when compared to other similar stars in regards to some of its physical properties, such as rotation. Considering that gyrochronology relations are widely used today to estimate ages of stars in the main sequence, and that the Sun is used to calibrate it, it is crucial to assess whether these procedures are acceptable. Aims. We analyze the rotational velocities, limited by the unknown rotation axis inclination angle, of an unprecedented large sample of solar twins to study the rotational evolution of Sun-like stars, and assess whether the Sun is a typical rotator. Methods. We used high-resolution (R = 115 000) spectra obtained with the HARPS spectrograph and the 3.6 m telescope at La Silla Observatory. The projected rotational velocities for 81 solar twins were estimated by line profile fitting with synthetic spectra. Macroturbulence velocities were inferred from a prescription that accurately reflects their dependence with effective temperature and luminosity of the stars. Results. Our sample of solar twins include some spectroscopic binaries with enhanced rotational velocities, and we do not find any nonspectroscopic binaries with unusually high rotation velocities. We verified that the Sun does not have a peculiar rotation, but the solar twins exhibit rotational velocities that depart from the Skumanich relation. Conclusions. The Sun is a regular rotator when compared to solar twins with a similar age. Additionally, we obtain a rotational braking law that better describes the stars in our sample (v ∝ t-0.6) in contrast to previous, often-used scalings