In order to enhance the efficiency of radio frequency identification (RFID) and lower system computational complexity, this paper proposes three novel tag anticollision protocols for passive RFID systems. The three proposed protocols are based on a binary tree slotted ALOHA (BTSA) algorithm. In BTSA, tags are randomly assigned to slots of a frame and if some tags collide in a slot, the collided tags in the slot will be resolved by binary tree splitting while the other tags in the subsequent slots will wait. The three protocols utilize a dynamic, an adaptive, and a splitting method to adjust the frame length to a value close to the number of tags, respectively. For BTSA, the identification efficiency can achieve an optimal value only when the frame length is close to the number of tags. Therefore, the proposed protocols efficiency is close to the optimal value. The advantages of the protocols are that, they do not need the estimation of the number of tags, and their efficiency is not affected by the variance of the number of tags. Computer simulation results show that splitting BTSA's efficiency can achieve 0.425, and the other two protocols efficiencies are about 0.40. Also, the results show that the protocols efficiency curves are nearly horizontal when the number of tags increases from 20 to 4,000.Index Terms-RFID, anticollision, ALOHA, estimation of the number of tags, passive Ç

The high cost of pixel-level annotations makes it appealing to train saliency detection models with weak supervision. However, a single weak supervision source usually does not contain enough information to train a wellperforming model. To this end, we propose a unified framework to train saliency detection models with diverse weak supervision sources. In this paper, we use category labels, captions, and unlabelled data for training, yet other supervision sources can also be plugged into this flexible framework. We design a classification network (CNet) and a caption generation network (PNet), which learn to predict object categories and generate captions, respectively, meanwhile highlight the most important regions for corresponding tasks. An attention transfer loss is designed to transmit supervision signal between networks, such that the network designed to be trained with one supervision source can benefit from another. An attention coherence loss is defined on unlabelled data to encourage the networks to detect generally salient regions instead of task-specific regions. We use CNet and PNet to generate pixel-level pseudo labels to train a saliency prediction network (SNet). During the testing phases, we only need SNet to predict saliency maps. Experiments demonstrate the performance of our method compares favourably against unsupervised and weakly supervised methods and even some supervised methods.

Rapid phenotypic changes in traits of adaptive significance are crucial for organisms to thrive in changing environments. How such phenotypic variation is achieved rapidly, despite limited genetic variation in species that experience a genetic bottleneck is unknown.Capsella rubella, an annual and inbreeding forb (Brassicaceae), is a great system for studying this basic question. Its distribution is wider than those of its congeneric species, despite an extreme genetic bottleneck event that severely diminished its genetic variation. Here, we demonstrate that transposable elements (TEs) are an important source of genetic variation that could account for its high phenotypic diversity. TEs are (i) highly enriched inC. rubellacompared with its outcrossing sister speciesCapsella grandiflora, and (ii) 4.2% of polymorphic TEs inC. rubellaare associated with variation in the expression levels of their adjacent genes. Furthermore, we show that frequent TE insertions atFLOWERING LOCUS C (FLC)in natural populations ofC. rubellacould explain 12.5% of the natural variation in flowering time, a key life history trait correlated with fitness and adaptation. In particular, we show that a recent TE insertion at the 3′ UTR ofFLCaffects mRNA stability, which results in reducing its steady-state expression levels, to promote the onset of flowering. Our results highlight that TE insertions can drive rapid phenotypic variation, which could potentially help with adaptation to changing environments in a species with limited standing genetic variation.

BackgroundPentatricopeptide-repeat proteins (PPRs) are characterized by tandem arrays of a degenerate 35-amino-acid (PPR motifs), which can bind RNA strands and participate in post-transcription. PPR proteins family is one of the largest families in land plants and play important roles in organelle RNA metabolism and plant development. However, the functions of PPR genes involved in biotic and abiotic stresses of rice (Oryza sativa L.) remain largely unknown.ResultsIn the present study, a comprehensive genome-wide analysis of PPR genes was performed. A total of 491 PPR genes were found in the rice genome, of which 246 PPR genes belong to the P subfamily, and 245 genes belong to the PLS subfamily. Gene structure analysis showed that most PPR genes lack intron. Chromosomal location analysis indicated that PPR genes were widely distributed in all 12 rice chromosomes. Phylogenetic relationship analysis revealed the distinct difference between the P and PLS subfamilies. Many PPR proteins are predicted to target chloroplasts or mitochondria, and a PPR protein (LOC_Os10g34310) was verified to localize in mitochondria. Furthermore, three PPR genes (LOC_Os03g17634,LOC_Os07g40820,LOC_Os04g51350) were verified as corresponding miRNA targets. The expression pattern analysis showed that many PPR genes could be induced under biotic and abiotic stresses. Finally, seven PPR genes were confirmed with their expression patterns under salinity or drought stress.ConclusionsWe found 491 PPR genes in the rice genome, and our genes structure analysis and syntenic analysis indicated that PPR genes might be derived from amplification by retro-transposition. The expression pattern present here suggested that PPR proteins have crucial roles in response to different abiotic stresses in rice. Taken together, our study provides a comprehensive analysis of the PPR gene family and will facilitate further studies on their roles in rice growth and development.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-5088-9) contains supplementary material, which is available to authorized users.

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