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Abstract In smart cities, the Internet-of-Thing (IoT) provides an enabling communication infrastructure to support tremendous amount of data exchange. Most IoT applications, e.g., wireless local area network, Bluetooth and so forth, utilize the channel-hopping scheme to suppress the transmission security threats. In this paper, to reduce the mutual interference and external jamming attacks, multiple novel channel-hopping patterns, i.e., traditional no-hit-zone (NHZ) hopping pattern and generalized NHZ hopping pattern, are introduced to suit to IoT networks. Particularly the design of probabilistic hopping pattern is first proposed, which has the various usage probabilities with regard to various channels. The properties of these hopping patterns are investigated by the step-to-step examples. Then, the error-rate performance of the multi-node IoT systems adopting these hopping patterns in the presence of jamming attacks is comprehensively analyzed. The extensive simulations show that the traditional/generalized NHZ hopping patterns are in favor of combating the mutual interference but with the limited capability of reducing jamming attacks, while the probabilistic hopping pattern possesses the opposite feature, that is, it has the predominant merit in suppressing jamming attacks. Thus, the novel channel-hopping pattern-based IoT could provide the secure transmission for communication applications in smart cities. Note that, as the physical-layer security technique, the channel-hopping patterns investigated in this paper are convenient to integrate with the security policies implemented in upper layers (e.g., encryption, authentication and so forth).

Abstract Background The large family of pentatricopeptide repeat (PPR) proteins is widely distributed among land plants. Such proteins play vital roles in intron splicing, RNA editing, RNA processing, RNA stability and RNA translation. However, only a small number of PPR genes have been identified in rice. Results In this study, we raised a mutant from tissue-culture-derived plants of Oryza sativa subsp. japonica ‘Zhonghua 11’, which exhibited a lethal chlorosis phenotype from germination to the third-leaf stage. The mutant was designated seedling-lethal chlorosis 1 (slc1). The slc1 mutant leaves showed extremely low contents of photosynthetic pigments and abnormal chloroplast development, and were severely defective in photosynthesis. Map-based cloning of OsSLC1 revealed that a single base (G) deletion was detected in the first exon of Os06g0710800 in the slc1 mutant, which caused a premature stop codon. Knockout and complementation experiments further confirmed that OsSLC1 is responsible for the seedling-lethal chlorosis phenotype in the slc1 mutant. OsSLC1 was preferentially expressed in green leaves, and encoded a chloroplast-localized PPR protein harboring 12 PPR motifs. Loss-of-function of OsSLC1 affected the intron splicing of multiple group II introns, and especially precluded the intron splicing of rps16, and resulted in significant increase in the transcript levels of 3 chloroplast ribosomal RNAs and 16 chloroplast development-related and photosynthesis-related genes, and in significant reduction in the transcript levels of 1 chloroplast ribosomal RNAs and 2 chloroplast development-related and photosynthesis-related genes. Conclusion We characterized a novel chloroplast-localized PPR protein, OsSLC1, which plays a vital role in the intron splicing of multiple group II introns, especially the rps16 intron, and is essential for early chloroplast development and seedling survival in rice.

Abstract The WSe2nanorods were synthesized via solid-state reaction method and characterized by X-ray diffractometer, TEM, and HRTEM. The results indicated the WSe2compounds had rod-like structures with diameters of 10–50 nm and lengths of 100–400 nm, and the growth process of WSe2nanorods was discussed on the basis of the experimental facts. The tribological properties of WSe2nanorods as additives in HVI500 base oil were investigated by UMT-2 multispecimen tribotester. Under the determinate conditions, the friction coefficient of the base oil containing WSe2nanorods was lower than that of the base oil, and decreased with increasing mass fraction of WSe2nanorods when it was 2nanorods as additives.

Abstract This letter addresses the problem of spectrum sensing over fading channel, in which a licensee and multiple unlicensed users coexist and operate in the licensed channel in a local area. We derive the overall average probabilities of detection and false alarm by jointly taking the fading and the location of SUs into account and employing the energy detection as the underlying detection scheme. Furthermore, we develop a statistical model of cumulate interference by the help of the overall average probabilities of detection. Based on the cumulate interference, we also obtain a closed-form expression of outage probability at the primary user's receiver according to a specific distribution of the fading.

This paper initiatively puts forward a novel synthesis design for generating UWB narrow pulse by using CI (Carrier Interference) subcarrier waveform synthesis and Bessel function expansion. Through adaptively adjusting the initial phases of multiple sub-carriers according to the location information, CI (Carrier Interference) sub-carrier waveform synthesis signal could achieve better performance. More specifically, when the carrier arrives at the receiver with a particular phase, the dynamic change of this signal amplitude can be significantly reduced by introducing sinusoidal frequency modulation signals. The method has significance for improving the overall performance of UWB communication system. This paper gives theoretical analysis and computer simulation results as well as the functional block diagram.