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  • Color-coordinate system from a 13th-century account of rainbows.

    1 March 2018

    We present a new analysis of Robert Grosseteste's account of color in his treatise De iride (On the Rainbow), dating from the early 13th century. The work explores color within the 3D framework set out in Grosseteste's De colore [see J. Opt. Soc. Am. A29, A346 (2012)], but now links the axes of variation to observable properties of rainbows. We combine a modern understanding of the physics of rainbows and of human color perception to resolve the linguistic ambiguities of the medieval text and to interpret Grosseteste's key terms.

  • Ongoing neurogenesis in the adult dentate gyrus mediates behavioral responses to ambiguous threat cues.

    12 December 2017

    Fear learning is highly adaptive if utilized in appropriate situations but can lead to generalized anxiety if applied too widely. A role of predictive cues in inhibiting fear generalization has been suggested by stress and fear learning studies, but the effects of partially predictive cues (ambiguous cues) and the neuronal populations responsible for linking the predictive ability of cues and generalization of fear responses are unknown. Here, we show that inhibition of adult neurogenesis in the mouse dentate gyrus decreases hippocampal network activation and reduces defensive behavior to ambiguous threat cues but has neither of these effects if the same negative experience is reliably predicted. Additionally, we find that this ambiguity related to negative events determines their effect on fear generalization, that is, how the events affect future behavior under novel conditions. Both new neurons and glucocorticoid hormones are required for the enhancement of fear generalization following an unpredictably cued threat. Thus, adult neurogenesis plays a central role in the adaptive changes resulting from experience involving unpredictable or ambiguous threat cues, optimizing behavior in novel and uncertain situations.

  • The group II metabotropic glutamate receptor agonist LY354740 and the D2 receptor antagonist haloperidol reduce locomotor hyperactivity but fail to rescue spatial working memory in GluA1 knockout mice.

    26 February 2018

    Group II metabotropic glutamate receptor agonists have been suggested as potential anti-psychotics, at least in part, based on the observation that the agonist LY354740 appeared to rescue the cognitive deficits caused by non-competitive N-methyl-d-aspartate receptor (NMDAR) antagonists, including spatial working memory deficits in rodents. Here, we tested the ability of LY354740 to rescue spatial working memory performance in mice that lack the GluA1 subunit of the AMPA glutamate receptor, encoded by Gria1, a gene recently implicated in schizophrenia by genome-wide association studies. We found that LY354740 failed to rescue the spatial working memory deficit in Gria1-/-mice during rewarded alternation performance in the T-maze. In contrast, LY354740 did reduce the locomotor hyperactivity in these animals to a level that was similar to controls. A similar pattern was found with the dopamine receptor antagonist haloperidol, with no amelioration of the spatial working memory deficit in Gria1-/-mice, even though the same dose of haloperidol reduced their locomotor hyperactivity. These results with LY354740 contrast with the rescue of spatial working memory in models of glutamatergic hypofunction using non-competitive NMDAR antagonists. Future studies should determine whether group II mGluR agonists can rescue spatial working memory deficits with other NMDAR manipulations, including genetic models and other pharmacological manipulations of NMDAR function.

  • Calling Dunbar's numbers

    12 March 2018

    © 2016 The Authors The social brain hypothesis predicts that humans have an average of about 150 relationships at any given time. Within this 150, there are layers of friends of an ego, where the number of friends in a layer increases as the emotional closeness decreases. Here we analyse a mobile phone dataset, firstly, to ascertain whether layers of friends can be identified based on call frequency. We then apply different clustering algorithms to break the call frequency of egos into clusters and compare the number of alters in each cluster with the layer size predicted by the social brain hypothesis. In this dataset we find strong evidence for the existence of a layered structure. The clustering yields results that match well with previous studies for the innermost and outermost layers, but for layers in between we observe large variability.

  • Comment: Respecifying Emotional Influence.

    16 March 2018

    To what extent does the level of overlap between social appraisal and social referencing depend upon the particular definitions adopted when following different research agendas? I argue that processes of both kinds fall under the more inclusive heading of relation alignment. Relation alignment also covers emotional influence that is not mediated by the communication of appraisal. Similarities, interdependences, and distinctions between these various relation-alignment processes warrant further investigation.

  • The role of organizational factors in achieving reliability in the design and manufacture of subsea equipment

    27 October 2017

    Failures of equipment used in deepwater oil and gas production are potentially hazardous, difficult and costly to rectify, and damaging to the environment; a high degree of reliability over many years of continuous operation is therefore an essential requirement of subsea systems. Although technical issues have been widely investigated, less is known about the organizational factors that promote high reliability in the design, manufacture, and installation of these systems. This review draws on studies of high-reliability manufacturing and process industries to examine the roles of intraorganizational factors (particularly organizational culture) that may promote or detract from the achievement of high reliability in subsea systems. External factors, such as supply chain coordination, are also considered. Studies of organizational change designed to enhance the reliability of design and manufacturing processes are rare in the subsea industry, but relevant issues arising from change initiatives in other organizational settings are discussed. Finally, several areas are identified in which systematic industry-based research could contribute to identifying critical elements in the development and operation of subsea systems and, hence, reduce the risk of failures. © 2011 Wiley Periodicals, Inc. © 2011 Wiley Periodicals, Inc., A Wiley Company.