XLVII.— On new forms of South-American birds

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Terrorism: The Case of Donbas and Ukraine

In 2014, the Crimean Peninsula was pseudo-legally annexed by the Russian Federation after months of internal turmoil (the “Euromaidan crisis”) that ousted then-President Viktor Yanukovych. This crisis, which began in November 2013, would turn into the most intense conflict in Eastern Europe since the Russian Federation was formed in the aftermath of the fall of the Soviet Union. The annexation, along with the declaration of independence by the oblasts of Donetsk and Lugansk would see several non-state actors (notably the People’s Republic of Donetsk, the People’s Republic of Lugansk, and Cossack Separatists) rise in opposition to the pro-Western forces in Ukraine. The sum result is a complex, multiparty conflict essentially frozen in a ceasefire declared in 2015 as a result of the Minsk Protocol (II)

A new R package and web application for detecting bilateral asymmetry in parasitic infections.

When parasites invade paired structures of their host non-randomly, the resulting asymmetry may have both pathological and ecological significance. To facilitate the detection and visualisation of asymmetric infections we have developed a free software tool, Analysis of Symmetry of Parasitic Infections (ASPI). This tool has been implemented as an R package (https://cran.r-project.org/package=aspi) and a web application (https://wayland.shinyapps.io/aspi). ASPI can detect both consistent bias towards one side, and inconsistent bias in which the left side is favoured in some hosts and the right in others. Application of ASPI is demonstrated using previously unpublished data on the distribution of metacercariae of species of Diplostomum von Nordmann, 1832 in the eyes of ruffe Gymnocephalus cernua (Linnaeus). Invasion of the lenses appeared to be random, with the proportion of metacercariae in the left and right lenses showing the pattern expected by chance. However, analysis of counts of metacercariae from the humors, choroid and retina revealed asymmetry between eyes in 38% of host fish

Adaptive division of growth and development between hosts in helminths with two‐host life cycles

Parasitic worms (helminths) with complex life cycles divide growth and development between successive hosts. Using data from 597 species of acanthocephalans, cestodes, and nematodes with two‐host life cycles, we found that helminths with larger intermediate hosts were more likely to infect larger, endothermic definitive hosts, although some evolutionary shifts in definitive host mass occurred without changes in intermediate host mass. Life‐history theory predicts parasites to shift growth to hosts in which they can grow rapidly and/or safely. Accordingly, helminth species grew relatively less as larvae and more as adults if they infected smaller intermediate hosts and/or larger, endothermic definitive hosts. Growing larger than expected in one host, relative to host mass/endothermy, was not associated with growing less in the other host, implying a lack of cross‐host trade‐offs. Rather, some helminth orders had both large larvae and large adults. Within these taxa, however, size at maturity in the definitive host was unaffected by changes to larval growth, as predicted by optimality models. Parasite life‐history strategies were mostly (though not entirely) consistent with theoretical expectations, suggesting that helminths adaptively divide growth and development between the multiple hosts in their complex life cycles.Peer Reviewe

A 'dipper' function for texture discrimination based on orientation variance

We measured the just-noticeable difference (JND) in orientation variance between two textures ( Figure 1) as we varied the baseline (pedestal) variance present in both textures. JND's first fell as pedestal variance increased and then rose, producing a ‘dipper’ function similar to those previously reported for contrast, blur, and orientation-contrast discriminations. A dipper function (both facilitation and masking) is predicted on purely statistical grounds by a noisy variance-discrimination mechanism. However, for two out of three observers, the dipper function was significantly better fit when the mechanism was made incapable of discriminating between small sample variances. We speculate that a threshold nonlinearity like this prevents the visual system from including its intrinsic noise in texture representations and suggest that similar thresholds prevent the visibility of other artifacts that sensory coding would otherwise introduce, such as blur

Perceived pattern regularity computed as a summary statistic: implications for camouflage

Why do the equally spaced dots in figure 1 appear regularly spaced? The answer ‘because they are’ is naive and ignores the existence of sensory noise, which is known to limit the accuracy of positional localization. Actually, all the dots in figure 1 have been physically perturbed, but in the case of the apparently regular patterns to an extent that is below threshold for reliable detection. Only when retinal pathology causes severe distortions do regular grids appear perturbed. Here, we present evidence that low-level sensory noise does indeed corrupt the encoding of relative spatial position, and limits the accuracy with which observers can detect real distortions. The noise is equivalent to a Gaussian random variable with a standard deviation of approximately 5 per cent of the inter-element spacing. The just-noticeable difference in positional distortion between two patterns is smallest when neither of them is perfectly regular. The computation of variance is statistically inefficient, typically using only five or six of the available dots

Education Reform for the Digital Era

Will the digital-learning movement repeat the mistakes of the charter-school movement? How much more successful might today's charter universe look if yesterday's proponents had focused on the policies and practices needed to ensure its quality, freedom, and resources over the long term? What mistakes might have been avoided? Damaging scandals forestalled? Missed opportunities seized