A gradient index metamaterial

Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult to achieve with existing materials. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index-of-refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a broad range of frequencies. The gradient index metamaterial represents an alternative approach to the development of gradient index lenses and similar optics that may be advantageous, especially at higher frequencies. In particular, the gradient index material we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated

Stress Fractures of the Elbow in the Throwing Athlete: A Systematic Review.

Background: Stress fractures of the elbow are rare in throwing athletes and present a challenge from both a management and rehabilitation perspective. Although the incidence of stress fractures of the elbow is increasing, there is a lack of data in the literature focused on throwers. Purpose: To evaluate studies regarding the management and outcomes of stress fractures of the elbow in throwing athletes. Study Design: Systematic review; Level of evidence, 4. Methods: A systematic review was conducted by searching the Scopus, PubMed, and Cochrane Library electronic databases to identify studies reporting on the management and outcomes of stress fractures in overhead-throwing athletes. Management data included nonoperative and operative modalities, and outcome data included return to play, encompassing the timing and level of activity. Studies were excluded if the stress fracture of the elbow was not a result of a sport injury attributed to throwing or if the study failed to report whether an athlete returned to play. Results: Fourteen studies met the inclusion criteria and were included in this analysis. There were 52 patients in total (50 male, 2 female) with a mean age of 19.7 years (range, 13-29.1 years). The olecranon was the most common location of the stress fracture (51 patients; 98.1%), followed by the distal humerus (1 patient; 1.9%). The majority of patients (n = 40; 76.9%) were treated operatively. Of the 40 patients who were treated surgically, 14 (35.0%) underwent a period of conservative treatment preoperatively that ultimately failed because of persistent nonunion or continued elbow pain. A total of 50 patients (96.2%) returned to sport either at or above their preinjury level. Of the 2 patients (3.8%) who did not return to sport, 1 did not return because of continued elbow pain postoperatively, and the other was lost to follow-up. Complications occurred in 9 patients (17.3%), all of whom were treated surgically. Conclusion: On the basis of this systematic review, the majority of elbow stress fractures were treated operatively and approximately one-third after a period of failed nonoperative management. The return-to-sport rate was high. Further, higher level studies are needed to optimize management and return-to-sport rates in this population

Computational simulation of human perception of spatially-dependent patterns modulated by degree and angle of linear polarization

Recent studies on polarization perception have shown that humans are sensitive to patterned stimuli modulated by either angle of linear polarization (AoP) or degree of polarization (DoP). Here, we present a model of human polarization sensitivity that incorporates both AoP and DoP as spatially dependent input variables. Applying the model to both sinusoidal- and square-wave-modulated DoP and AoP inputs, we demonstrate the theoretical similarities and differences generated by such inputs. Our model indicates the following: (i) edge boundaries between two adjacent areas of different linear polarization are preserved for both AoP- and DoP-modulated stimuli; and (ii) compared with DoP stimuli, AoP stimuli generate greater luminance changes at the photoreceptor level, suggesting that AoP-modulated patterns are potentially more salient than DoP patterns. The computational model is supported experimentally with an optical test of the model comprising a radial diattenuating polarizing filter and modified liquid crystal displays generating DoP- and AoP-modulated outputs. Psychophysical measures of human sensitivity confirm the increased salience of AoP- relative to DoP-modulated stimuli. These findings have practical application to the selection of DoP- and AoP-modulated stimuli for the investigation of macular function and macular pigment density in healthy and diseased eyes

Polarization perception in humans: on the origin of and relationship between Maxwell’s spot and Haidinger’s brushes

Under specific conditions of illumination and polarization, differential absorption of light by macular pigments is perceived as the entoptic phenomena of Maxwell’s spot (MS) or Haidinger’s brushes (HB). To simulate MS and HB, an existing computational model of polarization-dependent properties of the human macula was extended by incorporating neuronal adaptation to stabilized retinal images. The model predicted that polarized light modifies the appearance of MS leading to the perception of a novel phenomenon. The model also predicted a correlation between the observed diameters of MS and HB. Predictions were tested psychophysically in human observers, whose measured differences in the diameters of each entoptic phenomenon generated with depolarized and linearly polarized light were consistent with the model simulations. These findings support a common origin of each phenomenon, and are relevant to the clinical use of polarization stimuli in detecting and monitoring human eye disorders, including macular degeneration. We conclude: (i) MS and HB both result from differential light absorption through a radial diattenuator, compatible with the arrangement of macular pigments in Henle fibres; (ii) the morphology of MS is dependent on the degree of linear polarization; (iii) perceptual differences between MS and HB result from different states of neural adaptation

Quarantine Mothering and Working at Home: How Institutions of Higher Education Supported (or Failed to Support) Academic Mothers

This mixed methods study explores whether and how explicit policies, implicit practices, and internal communication from university administrators about aca-demic mothers’ work lives and expectations were impacted by the 2020 COVID-19 quarantine protocols. As this was a large study focussing on university policies addressing the presence of children on campus and the ways in which their enforcement or nonenforcement affected the personal and professional lives of faculty, we used purposive sampling (Palys) and snowball sampling (Patton) to distribute a survey in academic social media groups and to professional organization listservs (Palys). Among other things, the survey asked participants to report how well they thought their university was handling the COVID-19 pandemic and invited them to participate in an in-depth interview. As a result of the survey responses, we subsequently interviewed nineteen academic mothers from a range of academic disciplines, ages, and types of institutions, until we reached theoretical saturation (Strauss and Corbin). The semi-structured interview protocol included questions about the impact of COVID-19-related policies, practices, and messaging regarding children on participants’ job satisfaction, mental and physical health, as well as work-life balance. We used open and axial coding (Strauss and Corbin) and the constant comparative method (Glaser and Strauss) to analyze the data. We then triangulated the data by comparing interview and survey findings, engaging multiple researchers in the analysis, and conducting peer debriefings (Denzin and Lincoln; Lincoln and Guba). Findings highlight institutional policies and practices that serve or fail to serve faculty in terms of supporting their professional advancement in teaching, research, and service

Large bubble rupture sparks fast liquid jet

This Letter presents the novel experimental observation of long and narrow jets shooting out in disconnecting large elongated bubbles. We investigate this phenomenon by carrying out experiments with various viscosities, surface tensions, densities and nozzle radii. We propose a universal scaling law for the jet velocity, which unexpectedly involves the bubble height to the power 3/2. This anomalous exponent suggests an energy focusing phenomenon. We demonstrate experimentally that this focusing is purely gravity-driven and independent of the pinch-off singularity

Squidpops: A Simple Tool to Crowdsource a Global Map of Marine Predation Intensity

We present a simple, standardized assay, the squidpop, for measuring the relative feeding intensity of generalist predators in aquatic systems. The assay consists of a 1.3-cm diameter disk of dried squid mantle tethered to a rod, which is either inserted in the sediment in soft-bottom habitats or secured to existing structure. Each replicate squidpop is scored as present or absent after 1 and 24 hours, and the data for analysis are proportions of replicate units consumed at each time. Tests in several habitats of the temperate southeastern USA (Virginia and North Carolina) and tropical Central America (Belize) confirmed the assay’s utility for measuring variation in predation intensity among habitats, among seasons, and along environmental gradients. In Belize, predation intensity varied strongly among habitats, with reef\u3eseagrass = mangrove\u3eunvegetated bare sand. Quantitative visual surveys confirmed that assayed feeding intensity increased with abundance and species richness of fishes across sites, with fish abundance and richness explaining up to 45% and 70% of the variation in bait loss respectively. In the southeastern USA, predation intensity varied seasonally,being highest during summer and declining in late autumn. Deployments in marsh habitats generally revealed a decline in mean predation intensity from fully marine to tidal freshwater sites. The simplicity, economy, and standardization of the squidpop assay should facilitate engagement of scientists and citizens alike, with the goal of constructing high-resolution maps of how top-down control varies through space and time in aquatic ecosystems, and addressing a broad array of long-standing hypotheses in macro- and community ecolog