Biodiversity shapes tree species aggregations in tropical forests

Spatial patterns of conspecific trees are considered as the consequences of biological interactions and environmental influences. They also reflect species interactions in plant communities. However, biological attributes are often neglected while deliberating the factors shaping species distributions. As rising attentions are paid to spatial patterns of tropical forest trees, we noticed that seven Center of Tropical Forest Sites and four Forest Dynamic Plots in Asia and America have presented analogously high proportions of species with aggregated conspecific individuals coincidently. This phenomenon is distinctive and repudiates fundamental ecology hypotheses which suggested dispersed distributions of conspecific tropical trees due to intensive density and natural enemy pressures in tropical forests. We believe that similar aggregation patterns shared by these tropical forests implies the existence of structuring forces in biogeographical scale instead of habitat heterogeneity in local community scales as scientists have considered. To approach the factors contributing to this cross-continent spatial pattern of trees, we obtained and reviewed ecosystem attributes, including topography, temperature, precipitation, biodiversity, density, and biomass, of these forests. Here we show that the proportions of aggregated species are actually constants independent of any ecosystem attributes regardless the nature of these tropical forests. However, local biodiversity are the major factor determining the number of aggregated species and the aggregation of large individuals of these forests. Aggregation of large trees declines along rising biodiversity, while the numbers of aggregated species increase permanently along lifting biodiversity. We propose a possible equilibrium and saturated status of the tropical forests in accommodating aggregated species. Furthermore, the tight correlations of biodiversity and species aggregation strongly imply the importance of overlooked biological interactions in shaping the spatial patterns in the tropical forests

Two-Way Training for Discriminatory Channel Estimation in Wireless MIMO Systems

This work examines the use of two-way training to efficiently discriminate the channel estimation performances at a legitimate receiver (LR) and an unauthorized receiver (UR) in a multiple-input multiple-output (MIMO) wireless system. This work improves upon the original discriminatory channel estimation (DCE) scheme proposed by Chang et al where multiple stages of feedback and retraining were used. While most studies on physical layer secrecy are under the information-theoretic framework and focus directly on the data transmission phase, studies on DCE focus on the training phase and aim to provide a practical signal processing technique to discriminate between the channel estimation performances at LR and UR. A key feature of DCE designs is the insertion of artificial noise (AN) in the training signal to degrade the channel estimation performance at UR. To do so, AN must be placed in a carefully chosen subspace based on the transmitter's knowledge of LR's channel in order to minimize its effect on LR. In this paper, we adopt the idea of two-way training that allows both the transmitter and LR to send training signals to facilitate channel estimation at both ends. Both reciprocal and non-reciprocal channels are considered and a two-way DCE scheme is proposed for each scenario. {For mathematical tractability, we assume that all terminals employ the linear minimum mean square error criterion for channel estimation. Based on the mean square error (MSE) of the channel estimates at all terminals,} we formulate and solve an optimization problem where the optimal power allocation between the training signal and AN is found by minimizing the MSE of LR's channel estimate subject to a constraint on the MSE achievable at UR. Numerical results show that the proposed DCE schemes can effectively discriminate between the channel estimation and hence the data detection performances at LR and UR.Comment: 1

Efficiency of Digital Technology Use in Schools

Digital technologies in education are increasingly garnering much interest. Teachers and instructors play a fundamental role in ensuring that student-centered learning is the highlight of the application of digital technologies. The research focuses on the efficiency of digital technology in schools, with teachers as a mediating factor. Through the Technological Pedagogical and Content Knowledge (TPACK) framework, teachers\u27 competence and engagement play a critical role in technology application and digital technologies\u27 overall efficiency. In the study, we will conduct a quantitative research on the efficiency of digital technology use in schools

Light people: professor Martin Booth spoke about adaptive optics and its applications

Adaptive optics (AO), a technique originally introduced by astronomers to correct for optical distortions when looking at distant stars, now benefits the entire optics and photonics society. Prof. Martin Booth, who leads his research lab at the University of Oxford where he started his career, was one of the first people to take advantage of AO for microscopy. Since then, he has been continuously promoting the wide application of AO in all aspects of biological research and material science. As one of the few people who has witnessed the growth of AO in various communities, Prof. Martin Booth talks about their major differences, as well as their current challenges and future development. He discusses how AO can benefit emerging areas and the key challenges that may be faced. Prof. Martin Booth has also been making continuous efforts in removing the barriers of AO so that it can be promoted towards the wider community. Finally, he shares his experience from actively taking up different roles in education and in various societies and provides valuable advice to all early career researchers on the wisdom of being successful in their future careers. It is an honour for us to invite Prof. Martin Booth on this issue, and to learn from his inspirations, enthusiasm, and dedication

2-(4-Fluoro­phen­yl)-4-(4-meth­oxy­phen­yl)-5-(piperidin-1-ylmeth­yl)thia­zole

In the title compound, C22H23FN2OS, the piperidine ring shows chair confirmation and the two benzene rings make a dihedral angle of 17.0 (6)°. The thia­zole fragment is essentially planar with an r.m.s. deviation of 0.004 (2) Å and a maximum deviation of 0.006 (2) Å.. In the crystal, inter­molecular C—H⋯π inter­actions lead to the formation of a layer structure