Coulomb engineering of two-dimensional Mott materials.

Two-dimensional materials can be strongly influenced by their surroundings. A dielectric environment screens and reduces the Coulomb interaction between electrons in the two-dimensional material. Since in Mott materials the Coulomb interaction is responsible for the insulating state, manipulating the dielectric screening provides direct control over Mottness. Our many-body calculations reveal the spectroscopic fingerprints of such Coulomb engineering: we demonstrate eV-scale changes to the position of the Hubbard bands and show a Coulomb engineered insulator-to-metal transition. Based on our proof-of-principle calculations, we discuss the (feasible) conditions under which our scenario of Coulomb engineering of Mott materials can be realized experimentally.

Pre-participation Vision Screening and Comprehensive Eye Care in National Collegiate Athletic Association Athletes.

SIGNIFICANCE: Pre-participation physical evaluation and its vision screenings have been the mainstay of medical clearance for competitive play for decades. The ability of screening to address athlete's sports-specific vision needs is unknown. METHODS: Fifty-eight intercollegiate football players consented to participate in a comprehensive, sports-specific eye examination in addition to the standard pre-participation vision screening. Sensitivity, specificity, and positive and negative predictive values were determined for screening's ability to detect athletes whose vision might improve with correction, athletes who had significant ocular findings that impact safety, and either of the two conditions together. The effect no recent eye examination added to pre-participation vision screening results was evaluated for change in screening yield. Descriptive statistics of the cohort and associations with no recent comprehensive eye examination were generated. RESULTS: The pre-participation vision screening was able to identify three athletes not meeting visual acuity requirements for medical clearance to play without a comprehensive assessment. A failed screening was poorly able to identify athletes who might benefit from improved acuity (sensitivity, 9.1%; specificity, 100%), have sports-specific significant ocular findings (sensitivity, 10.5%; specificity, 97.3%), or have either together (sensitivity, 7.5%; specificity, 100%). Sixty percent (33/55) of athletes reported never having a comprehensive examination or one within the last 10 years. Fifty-eight percent (34/58) had improved best-corrected visual acuity after comprehensive examination, and 81% (47/58) had improved acuity or a sports-specific significant finding. CONCLUSIONS: The pre-participation vision screening was largely able to identify athletes meeting the minimum visual acuity requirement for athlete clearance. It poorly identified those who might benefit from improved vision with refractive correction and those in whom sport-specific significant eye findings were noted. Comprehensive eye care had a clear benefit for the majority of athletes tested. This benefit needs to be balanced with the potential added costs and time constraints to players and athletic department staff.

Objective Vision-related Indications for Clear and Tinted Football Helmet Visors.

SIGNIFICANCE: Football helmet visors are popular among players and may increase safety. However, they may also be costly or impractical, or impair the evaluation of head and neck injury. Determining an objective list of vision-related clinical conditions may help meet risk-benefit ratios while increasing access to care to athletes with special needs. PURPOSE: The purpose of this study was to determine an objective list of vision-related conditions that may benefit from clear and tinted football helmet visor use in athletes. METHODS: After comprehensive dilated eye examinations on 58 Division I collegiate football players at the University of Alabama at Birmingham between February 2017 and June 2018, an expert panel in vision care, sports medicine, and football equipment convened to determine vision-related conditions most important for clear or tinted football helmet visor use. RESULTS: In August 2018, the list drafted by the expert vision and sports medical panel in which a clear football helmet visor might be justified included conditions associated with retinal detachment and unilateral or binocular vision loss as well as high refractive error, refractive surgery, corneal compromise, and other conditions, which would necessitate additional eye protection. Of the 58 players examined, 3 (5%) were determined to have eye conditions that would require a clear visor as deemed by the expert panel, and 3 (5%) were determined to have eye conditions for which a clear visor was recommended. No players met indications for a tinted visor including congenital eye conditions that limit useful vision in daylight or bright-light environments, acquired conditions that may increase light sensitivity, and light-induced systemic conditions. CONCLUSIONS: This objective list of eye and vision-related systemic conditions is intended to mitigate the risk of long-term eye damage and/or vision deprivation. Clear and especially tinted football helmet visors require the sports medicine team to evaluate factors that will maximize the vision, head, and neck health of the athlete while increasing accessibility to sports for individuals with unique abilities.

Osmates on the Verge of a Hund's-Mott Transition: The Different Fates of NaOsO_{3} and LiOsO_{3}.

We clarify the origin of the strikingly different spectroscopic properties of the chemically similar compounds NaOsO_{3} and LiOsO_{3}. Our first-principle, many-body analysis demonstrates that the highly sensitive physics of these two materials is controlled by their proximity to an adjacent Hund's-Mott insulating phase. Although 5d oxides are mildly correlated, we show that the cooperative action of intraorbital repulsion and Hund's exchange becomes the dominant physical mechanism in these materials if their t_{2g} shell is half filled. Small material specific details hence result in an extremely sharp change of the electronic mobility, explaining the surprisingly different properties of the paramagnetic high-temperature phases of the two compounds.