The Influence of Time-Keeping Devices on Time Perception

The purpose of this study was to test the hypothesis that time-keeping devices influence our perception of time in a way apart from their usual role of telling time. The subjects obtained for this project consisted of forty-two students enrolled in freshman psychology courses at North Texas State University

Local to Continental-Scale Variation in the Richness and Composition of an Aquatic Food Web

Organismic and Evolutionary Biolog

Geographic Variation in Network Structure of a Nearctic Aquatic Food Web

Aim: The network structure of food webs plays an important role in the maintenance of diversity and ecosystem functioning in ecological communities. Previous research has found that ecosystem size, resource availability, assembly history and biotic interactions can potentially drive food web structure. However, the relative influence of climatic variables that drive broad-scale biogeographic patterns of species richness and composition has not been explored for food web structure. In this study, we assess the influence of broad-scale climatic variables in addition to known drivers of food web structure on replicate observations of a single aquatic food web, sampled from the leaves of the pitcher plant (Sarracenia purpurea), at different geographic sites across a broad latitudinal and climatic range. Location: Using standardized sampling methods, we conducted an extensive ‘snapshot’ survey of 780 replicated aquatic food webs collected from the leaves of the pitcher plant S. purpurea at 39 sites from northern Florida to Newfoundland and westward to eastern British Columbia. Methods: We examined correlations of 15 measures of food web structure at the pitcher and site scales with geographic variation in temperature and precipitation, concentrations of nutrients from atmospheric nitrogen deposition, resource availability, ecosystem size and the abundance of the pitcher plant mosquito (Wyeomyia smithii), a potential keystone species. Results: At the scale of a single pitcher plant leaf, linkage density, species richness, measures of chain length and the proportion of omnivores in a web all increased with pitcher volume. Linkage density and species richness were greater at high-latitude sites, which experience low mean temperatures and precipitation and high annual variation in both of these variables. At the site scale, variation in 8 of the 15 food web metrics decreased at higher latitudes, and variation in measures of chain length increased with the abundance of mosquitoes. Main conclusions: Ecosystem size and climatic variables related to latitude were most strongly correlated with network structure of the Sarracenia food web. However, in spite of large sample sizes, thorough standardized sampling and the large geographic extent of the survey, even the best-fitting models explained less than 40% of the variation in food web structure. In contrast to biogeographic patterns of species richness, food web structure was largely independent of broad-scale climatic variables. The large proportion of unexplained variance in our analyses suggests that stochastic assembly may be an important determinant of local food web structure.Organismic and Evolutionary Biolog

Observing Spontaneous Strong Parity Violation in Heavy-Ion Collisions

We discuss the problem of observing spontaneous parity and CP violation in collision systems. We discuss and propose observables which may be used in heavy-ion collisions to observe such violations, as well as event-by-event methods to analyze the data. Finally, we discuss simple monte-carlo models of these CP violating effects which we have used to develop our techniques and from which we derive rough estimates of sensitivities to signals which may be seen at RHIC

Microperimetry reliability assessed from fixation performance

Purpose: Microperimetry provides an accurate assessment of central retinal sensitivity due to its fundus-tracking capability, but it has limited reliability indicators. One method currently employed, fixation loss, samples the optic nerve blind spot for positive responses; however, it is unclear if these responses arise from unintentional button presses or from tracking failure leading to stimuli misplacement. We investigated the relationship between blind spot scotoma positive responses (termed scotoma responses) and fixation. Methods: Part 1 of the study involved a custom grid of 181 points centered on the optic nerve that was constructed to map physiological blind spots in primary and simulated eccentric fixation positions. Scotoma responses and the 63% and 95% fixation bivariate contour ellipse areas (BCEA63 and BCEA95) were analyzed. In Part 2, fixation data from controls and patients with retinal diseases (234 eyes from 118 patients) were collected. Results: Part 1, a linear mixed model of 32 control participants, demonstrated significant (P < 0.001) correlation between scotoma responses and BCEA95. In Part 2, the upper 95% confidence intervals for BCEA95 were 3.7 deg2 for controls, 27.6 deg2 for choroideremia, 23.1 deg2 for typical rod–cone dystrophies, 21.4 deg2 for Stargardt disease, and 111.3 deg2 for age-related macular degeneration. Incorporating all pathology groups into an overall statistic resulted in an upper limit BCEA95 = 29.6 deg2. Conclusions: Microperimetry reliability is significantly correlated to fixation performance, and BCEA95 provides a surrogate marker for test accuracy. Examinations of healthy individuals and patients with retinal disease are deemed unreliable if BCEA95 > 4 deg2 and BCEA95 > 30 deg2, respectively. Translational Relevance: Microperimetry reliability should be assessed using fixation performance as summarized by BCEA95 rather than the level of fixation losses

Early myogenic responses to acute exercise before and after resistance training in young men

To enable dynamic regulation of muscle mass and myofiber repair following injury, a satellite cell precursor population exists to supply additional nuclei. Activated satellite cells express many genes and associated proteins necessary for maturation and incorporation into the damaged fiber. There is little knowledge about the response of these markers following whole-body resistance exercise training. We investigated the impact of 12 weeks of progressive whole-body resistance training on the expression of MRFs, PAX7, NCAM, and FA1, incorporating both acute and chronic resistance exercise components. Ten young recreationally active males (21.2 ± 3.5 years) performed 12 weeks of whole-body resistance training at 70–85% of their predetermined one-repetition maximum (1RM). At the initiation and completion of the training period, muscular strength was assessed by RM and dynamometer testing, and vastus lateralis samples were obtained prior to and 3 h following an acute resistance exercise test (both whole-body and isometric exercises). Increased mRNA expression of PAX7 (threefold), NCAM (threefold), MYF5 (threefold), MYOD (threefold) and MYOGENIN (twofold) was observed 3 h after the acute resistance exercise test, both pre and posttraining. Similarly, PAX7 (11-fold) and FA1 (twofold) protein abundance increased after acute exercise, while resting NCAM (eightfold) and FA1 (threefold) protein abundance increased following 12 weeks of resistance training. It is possible that these molecular changes are primarily due to the preceding exercise bout, and are not modified by long-term or whole-body exercise training

Characterizing visual fields in RPGR related retinitis pigmentosa using octopus static-automated perimetry

Purpose: Peripheral visual fields have not been as well defined by static automated perimetry as kinetic perimetry in RPGR-related retinitis pigmentosa. This study explores the pattern and sensitivities of peripheral visual fields, which may provide an important end point when assessing interventional clinical trials. Methods: A retrospective observational cross-sectional study of 10 genetically confirmed RPGR subjects was performed. Visual fields were obtained using the Octopus 900 perimeter. Interocular symmetry and repeatability were quantified. Visual fields were subdivided into central and peripheral subfields for analysis. Results: Mean patient age was 32 years old (20 to 49 years old). Average mean sensitivity was 7 dB (SD = 3.67 dB) and 6.8 dB (SD = 3.4 dB) for the right and left eyes, respectively, demonstrating interocular symmetry. Coefficient of repeatability for overall mean sensitivity: <2 dB. Nine out of 10 subjects had a preserved inferotemporal subfield, whose mean sensitivity was highly correlated to the central field (r2 = 0.78, P = 0.002 and r2 = 0.72, P = 0.002 for the right and left eyes, respectively). Within the central field, sensitivities were greater in the temporal than the nasal half (t-test, P = 0.01 and P = 0.03 for the right and left eyes, respectively). Conclusions: Octopus static-automated perimeter demonstrates good repeatability. Interocular symmetry permits use of the noninterventional eye as an internal control. In this cohort, the inferotemporal and central visual fields are preserved into later disease stages likely mapping to populations of surviving cones. Translational Relevance: A consistently preserved inferotemporal island of vision highly correlated to that of the central visual field may have significance as a possible future therapeutic site

Microperimetry hill of vision and volumetric measures of retinal sensitivity

Purpose: Mean retinal sensitivity is the main output measure used in microperimetry. It is, however, of limited use in patients with poor vision because averaging is weighted toward zero in those with significant scotomas creating an artificial floor effect. In contrast, volumetric measures avoid these issues and are displayed graphically as a hill of vision. Methods: An open-source program was created to manipulate raw sensitivity threshold data files obtained from MAIA microperimetry. Thin plate spline interpolated heat maps and three-dimensional hill of vision plots with an associated volume were generated. Retrospective analyses of microperimetry volumes were undertaken in patients with a range of retinal diseases to assess the qualitative benefits of three-dimensional visualization and volumetric measures. Simulated pathology was applied to radial grid patterns to investigate the performance of volumetric sensitivity in nonuniform grids. Results: Volumetric analyses from microperimetry in RPGR-related retinitis pigmentosa, choroideremia, Stargardt disease, and age-related macular degeneration were analyzed. In simulated nonuniform testing grids, volumetric sensitivity was able to detect differences in retinal sensitivity where mean sensitivity could not. Conclusions: Volumetric measures do not suffer from averaging issues and demonstrate superior performance in nonuniform testing grids. Additionally, volume measures enable detection of localized retinal sensitivity changes that might otherwise be undetectable in a mean change. Translational Relevance: As microperimetry has become an outcome measure in several gene-therapy clinical trials, three-dimensional visualization and volumetric sensitivity enables a complementary analysis of baseline disease characteristics and subsequent response to treatment, both as a signal of safety and efficacy