Towards understanding wild boar Sus scrofa movement: a synthetic movement ecology approach

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Perceiving polarization with the naked eye: characterization of human polarization sensitivity

Like many animals, humans are sensitive to the polarization of light. We can detect the angle of polarization using an entoptic phenomenon called Haidinger''s brushes, which is mediated by dichroic carotenoids in the macula lutea. While previous studies have characterized the spectral sensitivity of Haidinger''s brushes, other aspects remain unexplored. We developed a novel methodology for presenting gratings in polarization-only contrast at varying degrees of polarization in order to measure the lower limits of human polarized light detection. Participants were, on average, able to perform the task down to a threshold of 56%, with some able to go as low as 23%. This makes humans the most sensitive vertebrate tested to date. Additionally, we quantified a nonlinear relationship between presented and perceived polarization angle when an observer is presented with a rotatable polarized light field. This result confirms a previous theoretical prediction of how uniaxial corneal birefringence impacts the perception of Haidinger''s brushes. The rotational dynamics of Haidinger''s brushes were then used to calculate corneal retardance. We suggest that psychophysical experiments, based upon the perception of polarized light, are amenable to the production of affordable technologies for self-assessment and longitudinal monitoring of visual dysfunctions such as age-related macular degeneration.     

Feasibility of remote magnetic navigation for epicardial ablation

Percutaneous epicardial mapping and ablation is an emerging method to treat ventricular tachycardias (VT), premature ventricular complexes (PVC), and accessory pathways. The use of a remote magnetic navigation system (MNS) could enhance precision and maintain safety. This multiple case history demonstrates the feasibility and safety of the MNS-guided epicardial approach in mapping and ablation of ischaemic VT, outflow tract PVCs, and a left-sided accessory pathway. All patients had previously undergone endocardial mapping for the same arrhythmia. MNS could present an advantage from more precise navigation for mapping and maintaining catheter stability during energy application.     

实时虚拟导航系统辅助超声引导下消融治疗肝癌患者疗效与安全性的系统评价

目的:系统评价实时虚拟导航系统辅助超声引导下射频消融治疗肝癌患者疗效与安全性,为临床治疗提供参考。方法:计算机检索Pubmed、EMbase、The Cochrane Library、Web of Science、WanFang Data、CNKI、CBM、VIP数据库,同时辅以其他检索,收集所有相关的临床对照试验,检索时限从各数据库建库起至2019年12月。由两位评价员分别独立根据纳入与排除标准对文献进行筛选、提取资料及质量评价,后采用RevMan 5.3软件进行分析。结果:共纳入6个队列研究,包括1845例患者。试验组为实时虚拟导航系统(Real-time Virtual Navigation System, RVS)辅助超声引导下(Ultrosound, US)/(Contrast Enhanced Ultrosound, CEUS)消融治疗肝癌组,即RVS+US/CEUS组,对照组为超声引导下消融治疗肝癌组,即US/CEUS组。分析结果显示:在提高肿瘤消融率方面,试验组显著优于对照组(P<0.05),在并发症发生率方面,试验组与对照组结局指标无统计学差异。结论:RVS辅助超声引导下射频消融治疗肝癌患者在提高肿瘤消融率方面优于传统超声引导下射频消融治疗。     

American Security and Law of the Sea

With the election of President Barack Obama and renewed interest in the Law of the Sea Convention inside the United States, this article pulls from obscurity the key U.S. declarations, understandings, and conditions of ratification to the Treaty, considers their context and meaning for U.S. security interests, and helps to place them into the lexicon of oceans law and policy that informs the greater dialogue of international security and strategy.     

Enhancing Port State Control in Polar Waters

Abstract

In recent years, the role of Port State Control (PSC) with respect to polar navigation has become increasingly important. However, international rules for PSC of fishing vessels plying polar waters are incomplete and uniform inspection guidelines have not yet been adopted, nor has a coordinated mechanism been created. This article argues that fishing vessels should be incorporated into the Polar Code and that at the practical level, states should promote the application of the Port State Control Officer Guidelines adopted under the Paris Memorandum of Understanding and encourage cooperation among the different PSC organizations that cover polar waters.     

Not just passengers: pigeons,Columba livia,can learn homing routes while flying with a more experienced conspecific

For animals that travel in groups, the directional choices of conspecifics are potentially a rich source of information for spatial learning. In this study, we investigate how the opportunity to follow a locally experienced demonstrator affects route learning by pigeons over repeated homing flights. This test of social influences on navigation takes advantage of the individually distinctive routes that pigeons establish when trained alone. We found that pigeons learn routes just as effectively while flying with a partner as control pigeons do while flying alone. However, rather than learning the exact route of the demonstrator, the paired routes shifted over repeated flights, which suggests that the birds with less local experience also took an active role in the navigational task. The efficiency of the original routes was a key factor in how far they shifted, with less efficient routes undergoing the greatest changes. In this context, inefficient routes are unlikely to be maintained through repeated rounds of social transmission, and instead more efficient routes are achieved because of the interaction between social learning and information pooling.     

磁场对蜜蜂行为影响的研究进展

地球内部存在着天然磁性现象,被称为地磁场。当今社会电子通讯发达,电磁波信号频繁,地球表面充满了电磁场。蜜蜂作为重要的授粉昆虫,其活动范围大部分都处于磁场环境中。目前研究者普遍认为蜜蜂能利用磁场进行导航,但环境中异常的磁场同样会影响蜜蜂的定位导航、飞行行为、采集活动和学习认知能力等。本文对前人的研究结果进行了综述,以期系统地了解磁场对蜜蜂行为特性的影响。     

On the trail of Vikings with polarized skylight: experimental study of the atmospheric optical prerequisites allowing polarimetric navigation by Viking seafarers

Between AD 900 and AD 1200 Vikings, being able to navigate skillfully across the open sea, were the dominant seafarers of the North Atlantic. When the Sun was shining, geographical north could be determined with a special sundial. However, how the Vikings could have navigated in cloudy or foggy situations, when the Sun's disc was unusable, is still not fully known. A hypothesis was formulated in 1967, which suggested that under foggy or cloudy conditions, Vikings might have been able to determine the azimuth direction of the Sun with the help of skylight polarization, just like some insects. This hypothesis has been widely accepted and is regularly cited by researchers, even though an experimental basis, so far, has not been forthcoming. According to this theory, the Vikings could have determined the direction of the skylight polarization with the help of an enigmatic birefringent crystal, functioning as a linearly polarizing filter. Such a crystal is referred to as 'sunstone' in one of the Viking's sagas, but its exact nature is unknown. Although accepted by many, the hypothesis of polarimetric navigation by Vikings also has numerous sceptics. In this paper, we summarize the results of our own celestial polarization measurements and psychophysical laboratory experiments, in which we studied the atmospheric optical prerequisites of possible sky-polarimetric navigation in Tunisia, Finland, Hungary and the high Arctic.