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Visual place recognition (VPR) is considered among the most challenging problems due to the extreme variations in appearance and viewpoint. Essentially, appearance-based VPR can be considered as an image retrieval task, thus the key is to accurately and efficiently describe the images. Recently, global descriptor methods have attracted substantial attention from the VPR community, which has contributed to numerous important outcomes. Despite the growing number of global descriptors presented, little attention has been paid to the comparison and evaluation of these methods and so it remains difficult for researchers to disentangle the factors that led to better performance. This study provided comprehensive insight into global descriptors from a practical application perspective. We present a systematic evaluation that integrates 15 commonly used global descriptors, 6 benchmark datasets, and 5 evaluation metrics, and subsequently extended this evaluation to discuss the key factors impacting the matching performance and computational efficiency. We also report practical suggestions for constructing promising CNN descriptors, based on the experimental conclusions. Our analysis reveals both advantages and limitations of three different types of global descriptors, including handcrafted features-based ones, off-the-shelf CNN-based ones, and customized CNN-based ones. Finally, we evaluate the practicality of reported global descriptors to mediate the trade-offs between matching performance and computational efficiency. [ABSTRACT FROM AUTHOR]

Aims Icariin ( ICA), a flavonoid isolated from epimedii, has been reported to have potential protective effects on the cardiovascular system. This study is to investigate the effect and the underlying mechanisms of ICA on ischemia/reperfusion (I/R) injury. Methods Wister rat hearts were subjected to I/R using Langendorff perfusion system. Cardiac function, myocardial infarct size, lactate dehydrogenase ( LDH), and creatine kinase- MB ( CK- MB) activities in coronary effluent, and superoxide dismutase ( SOD) and malondialdehyde ( MDA) content in heart tissue and cardiomyocyte apoptosis were assayed. Results Compared with the I/R group, ICA treatment significantly improved cardiac function, decreased myocardial infarct size, enzyme activity, oxidative stress, and apoptosis. In addition, ICA treatment lead to an increased p-Akt level, which was partially reversed by LY294002, a PI3 K pathway inhibitor. Conclusion Our study suggests that ICA has a cardioprotective effect against I/R injury, which is associated with its antioxidative and anti-apoptotic effect, at least partially, through the activation of PI3 K-Akt signaling pathway. [ABSTRACT FROM AUTHOR]