Evaluating Outer Segment Length as A Surrogate Measure of Peak Foveal Cone Density

Adaptive optics (AO) imaging tools enable direct visualization of the cone photoreceptor mosaic, which facilitates quantitative measurements such as cone density. However, in many individuals, low image quality or excessive eye movements precludes making such measures. As foveal cone specialization is associated with both increased density and outer segment (OS) elongation, we sought to examine whether OS length could be used as a surrogate measure of foveal cone density. The retinas of 43 subjects (23 normal and 20 albinism; aged 6–67 years) were examined. Peak foveal cone density was measured using confocal adaptive optics scanning light ophthalmoscopy (AOSLO), and OS length was measured using optical coherence tomography (OCT) and longitudinal reflectivity profile-based approach. Peak cone density ranged from 29,200 to 214,000 cones/mm2(111,700 ± 46,300 cones/mm2); OS length ranged from 26.3 to 54.5 μm (40.5 ± 7.7 μm). Density was significantly correlated with OS length in albinism (p \u3c 0.0001), but not normals (p = 0.99). A cubic model of density as a function of OS length was created based on histology and optimized to fit the albinism data. The model includes triangular cone packing, a cylindrical OS with a fixed volume of 136.6 μm3, and a ratio of OS to inner segment width that increased linearly with increasing OS length (R2 = 0.72). Normal subjects showed no apparent relationship between cone density and OS length. In the absence of adequate AOSLO imagery, OS length may be used to estimate cone density in patients with albinism. Whether this relationship exists in other patient populations with foveal hypoplasia (e.g., premature birth, aniridia, isolated foveal hypoplasia) remains to be seen

Forensic Science in Legal Education

In criminal cases, forensic science reports and expert testimony play an increasingly important role in adjudication. More states now follow a federal reliability standard, following Daubert v. Merrell Dow Pharmaceuticals and Rule 702, which calls upon judges to assess the reliability and validity of such scientific evidence. Little is known about what education law schools provide regarding forensic and scientific evidence or what types of specialized training they receive on scientific methods or evidence. Whether law schools have added forensic science courses to their curricula in recent years was not known. To better understand the answers to those questions, in late 2019 and spring 2020, we conducted searches to identify course offerings in forensic sciences at U.S. law schools and then surveyed their instructors, asking for syllabi and information concerning how the courses are offered, how regularly, and with what coverage. We identified just forty-three courses at law schools and received responses with more detailed information from twenty-two instructors. In this Article, we describe our findings, and situate them in the offerings of law schools regarding evidence, science, and quantitative methods. We suggest that forensic science will necessarily be a specialty subject at law schools that can and should be further taught in continuing education programs, but also that quantitative methods courses in law school may help provide the foundation for such continuing education

Wolbachia in the Drosophila yakuba Complex: Pervasive Frequency Variation and Weak Cytoplasmic Incompatibility, but No Apparent Effect on Reproductive Isolation

Three hybridizing species—the clade [(Drosophila yakuba, D. santomea), D. teissieri]—comprise the yakuba complex in the D. melanogaster subgroup. Their ranges overlap on Bioko and São Tomé, islands off west Africa. All three species are infected with Wolbachia—maternally inherited, endosymbiotic bacteria, best known for manipulating host reproduction to favor infected females. Previous analyses reported no cytoplasmic incompatibility (CI) in these species. However, we discovered that Wolbachia from each species cause intraspecific and interspecific CI. In D. teissieri, analyses of F1 and backcross genotypes show that both host genotype and Wolbachia variation modulate CI intensity. Wolbachia-infected females seem largely protected from intraspecific and interspecific CI, irrespective of Wolbachia and host genotypes. Wolbachia do not affect host mating behavior or female fecundity, within or between species. The latter suggests little apparent effect of Wolbachia on premating or gametic reproductive isolation (RI) between host species. In nature, Wolbachia frequencies varied spatially for D. yakuba in 2009, with 76% (N = 155) infected on São Tomé, and only 3% (N = 36) infected on Bioko; frequencies also varied temporally in D. yakuba and D. santomea on São Tomé between 2009 and 2015. These temporal frequency fluctuations could generate asymmetries in interspecific mating success, and contribute to postzygotic RI. However, the fluctuations in Wolbachia frequencies that we observe also suggest that asymmetries are unlikely to persist. Finally, we address theoretical questions that our empirical findings raise about Wolbachia persistence when conditions fluctuate, and about the stable coexistence of Wolbachia and host variants that modulate Wolbachia effects

Chandra Discovery of 10 New X-Ray Jets Associated With FR II Radio Core-Selected AGNs in the MOJAVE Sample

The Chandra X-ray observatory has proven to be a vital tool for studying high-energy emission processes in jets associated with Active Galactic Nuclei (AGN).We have compiled a sample of 27 AGN selected from the radio flux-limited MOJAVE (Monitoring of Jets in AGN with VLBA Experiments) sample of highly relativistically beamed jets to look for correlations between X-ray and radio emission on kiloparsec scales. The sample consists of all MOJAVE quasars which have over 100 mJy of extended radio emission at 1.4 GHz and a radio structure of at least 3" in size. Previous Chandra observations have revealed X-ray jets in 11 of 14 members of the sample, and we have carried out new observations of the remaining 13 sources. Of the latter, 10 have Xray jets, bringing the overall detection rate to ~ 78%. Our selection criteria, which is based on highly compact, relativistically beamed jet emission and large extended radio flux, thus provides an effective method of discovering new X-ray jets associated with AGN. The detected X-ray jet morphologies are generally well correlated with the radio emission, except for those displaying sharp bends in the radio band. The X-ray emission mechanism for these powerful FR II (Fanaroff-Riley type II) jets can be interpreted as inverse Compton scattering off of cosmic microwave background (IC/CMB) photons by the electrons in the relativistic jets. We derive viewing angles for the jets, assuming a non-bending, non-decelerating model, by using superluminal parsec scale speeds along with parameters derived from the inverse Compton X-ray model. We use these angles to calculate best fit Doppler and bulk Lorentz factors for the jets, as well as their possible ranges, which leads to extreme values for the bulk Lorentz factor in some cases. When both the non-bending and non-decelerating assumptions are relaxed [abridged]Comment: 38 Pages, 4 Figures, 5 Tables, accepted for publication in Ap

Isopods Failed to Acclimate Their Thermal Sensitivity of Locomotor Performance During Predictable or Stochastic Cooling

Most organisms experience environments that vary continuously over time, yet researchers generally study phenotypic responses to abrupt and sustained changes in environmental conditions. Gradual environmental changes, whether predictable or stochastic, might affect organisms differently than do abrupt changes. To explore this possibility, we exposed terrestrial isopods (Porcellio scaber) collected from a highly seasonal environment to four thermal treatments: (1) a constant 20 degrees C; (2) a constant 10 degrees C; (3) a steady decline from 20 degrees to 10 degrees C; and (4) a stochastic decline from 20 degrees to 10 degrees C that mimicked natural conditions during autumn. After 45 days, we measured thermal sensitivities of running speed and thermal tolerances (critical thermal maximum and chill-coma recovery time). Contrary to our expectation, thermal treatments did not affect the thermal sensitivity of locomotion; isopods from all treatments ran fastest at 33 degrees to 34 degrees C and achieved more than 80% of their maximal speed over a range of 10 degrees to 11 degrees C. Isopods exposed to a stochastic decline in temperature tolerated cold the best, and isopods exposed to a constant temperature of 20 degrees C tolerated cold the worst. No significant variation in heat tolerance was observed among groups. Therefore, thermal sensitivity and heat tolerance failed to acclimate to any type of thermal change, whereas cold tolerance acclimated more during stochastic change than it did during abrupt change

Unveiling the mechanisms of solid-state dewetting in Solid Oxide Cells with novel 2D electrodes

During the operation of Solid Oxide Cell (SOC) fuel electrodes, the mobility of nickel can lead to significant changes in electrode morphology, with accompanying degradation in electrochemical performance. In this work, the dewetting of nickel films supported on yttriastabilized zirconia (YSZ), hereafter called 2D cells, is studied by coupling in-situ environmental scanning electron microscopy (E-SEM), image analysis, cellular automata simulation and electrochemical impedance spectroscopy (EIS). Analysis of experimental E-SEM images shows that Ni dewetting causes an increase in active triple phase boundary (aTPB) length up to a maximum, after which a sharp decrease in aTPB occurs due to Ni de-percolation. This microstructural evolution is consistent with the EIS response, which shows a minimum in polarization resistance followed by a rapid electrochemical degradation. These results reveal that neither evaporation-condensation nor surface diffusion of Ni are the main mechanisms of dewetting at 560-800 °C. Rather, the energy barrier for pore nucleation within the dense Ni film appears to be the most important factor. This sheds light on the relevant mechanisms and interfaces that must be controlled to reduce the electrochemical degradation of SOC electrodes induced by Ni dewetting

The Reliability of Parafoveal Cone Density Measurements

Background Adaptive optics scanning light ophthalmoscopy (AOSLO) enables direct visualisation of the cone mosaic, with metrics such as cone density and cell spacing used to assess the integrity or health of the mosaic. Here we examined the interobserver and inter-instrument reliability of cone density measurements. Methods For the interobserver reliability study, 30 subjects with no vision-limiting pathology were imaged. Three image sequences were acquired at a single parafoveal location and aligned to ensure that the three images were from the same retinal location. Ten observers used a semiautomated algorithm to identify the cones in each image, and this was repeated three times for each image. To assess inter-instrument reliability, 20 subjects were imaged at eight parafoveal locations on one AOSLO, followed by the same set of locations on the second AOSLO. A single observer manually aligned the pairs of images and used the semiautomated algorithm to identify the cones in each image. Results Based on a factorial study design model and a variance components model, the interobserver study\u27s largest contribution to variability was the subject (95.72%) while the observer\u27s contribution was only 1.03%. For the inter-instrument study, an average cone density intraclass correlation coefficient (ICC) of between 0.931 and 0.975 was calculated. Conclusions With the AOSLOs used here, reliable cone density measurements can be obtained between observers and between instruments. Additional work is needed to determine how these results vary with differences in image quality

Patterns of Population Structure and Introgression Among Recently Differentiated \u3ci\u3eDrosophila melanogaster\u3c/i\u3e Populations

Despite a century of genetic analysis, the evolutionary processes that have generated the patterns of exceptional genetic and phenotypic variation in the model organism Drosophila melanogaster remains poorly understood. In particular, how genetic variation is partitioned within its putative ancestral range in Southern Africa remains unresolved. Here, we study patterns of population genetic structure, admixture, and the spatial structuring of candidate incompatibility alleles across a global sample, including 223 new accessions, predominantly from remote regions in Southern Africa. We identify nine major ancestries, six that primarily occur in Africa and one that has not been previously described. We find evidence for both contemporary and historical admixture between ancestries, with admixture rates varying both within and between continents. For example, while previous work has highlighted an admixture zone between broadly defined African and European ancestries in the Caribbean and southeastern USA, we identify West African ancestry as the most likely African contributor. Moreover, loci showing the strongest signal of introgression between West Africa and the Caribbean/southeastern USA include several genes relating to neurological development and male courtship behavior, in line with previous work showing shared mating behaviors between these regions. Finally, while we hypothesized that potential incompatibility loci may contribute to population genetic structure across the range of D. melanogaster; these loci are, on average, not highly differentiated between ancestries. This work contributes to our understanding of the evolutionary history of a key model system, and provides insight into the partitioning of diversity across its range