Search

Compared to traditional power grids, microgrids have a more flexible operating mode. There are various distributed power sources within the microgrid, and different types of distributed power sources have different control methods. Once a short-circuit fault occurs in the microgrid, these characteristics will increase the difficulty of microgrid fault diagnosis and reduce the accuracy of microgrid fault diagnosis. This paper proposes an error-correcting particle swarm optimization back propagation microgrid fault diagnosis method for the diagnosis of short-circuit faults in microgrids that identifies the accuracy of alarm signals, corrects unreasonable signals, and obtains the correct fault set of the microgrid through the temporal logic relationship between each protection. Using the particle swarm optimization back propagation (PSO-BP) neural network algorithm to train fault alarm signals, fast convergence can be achieved, and accurate diagnostic results can be obtained after the sixth generation training is completed. As this fault diagnosis algorithm is applied to line protection equipment, it can be used to diagnose all types of short-circuit faults. This algorithm is easy to implement and has a small data scale, which is conducive to efficient and concise fault diagnoses in microgrids.

Increasing evidences show that circRNAs are associated with some autoimmunity diseases either as a biomarker or therapeutic target. Exosomes containing nucleic acids and proteins are found in sera of series diseases and could serve as either diagnostic or therapeutic target. ANA serves as first common diagnostic test for autoimmunity disease, different ANA staining reflecting different types of autoimmunity disease. Till now, whether different ANA sera exosomes express different circRNAs and relevant ceRNA networks are still shortage of investigation. This study analyzed circRNAs, miRNAs, and their interaction networks in different ANA sera exosomes by high-throughput sequencing. It found no significant difference of total circRNAs and miRNAs amount across different ANA sera exosomes. However, significant differences were found of circRNAs, miRNA constituents, function analysis by KEGG and GO, and their ceRNA networks including miRNA-circRNA and miRNA-mRNA among different ANA sera exosomes, suggesting sera exosome circRNAs as either biomarker or mechanism of autoimmunity diseases.

In this paper, an improved dual neural network control method based on multi-agent system is proposed to solve the problem of rating the frequency deviation and voltage deviation of the microgrid system due to the uneven impedance distribution of the circuit. The microgrid multi-agent system control model is constructed; the microgrid operation problem is transformed into Markov decision-making process, and the frequency error model of distributed secondary control adjusting system is established. In the course of training, the priority experience replay mechanism is introduced to accelerate the training reward return by using the experience of high feedback reward, and the frequency and voltage bias of the microgrid system are reduced. The model of isolated island microgrid of distributed power supply communication topology is established, and the control strategy of double neural network is simulated. Compared with the traditional sagging control method, the double neural network algorithm proposed in this paper stabilizes the frequency of the grid at rated frequency and improves the convergence speed. Simulation results show that the proposed method is helpful to provide stable and high-quality power resources for enterprises.

According to the characteristics of ploughing extrusion forming and the theory of metal cutting, the wear and damage mechanism, common wear and damage forms and causes of multi-tooth tools in ploughing extrusion forming are analyzed. Then, the correctness of the analysis of tool wear and damage mechanism and common wear and damage forms is verified by field cutting experiments. At the same time, the phenomena and causes of workpiece stagnation and cracks in the process of ploughing and extrusion forming were obtained through experiments. Finally, the reasonable processing parameters of ploughing and extrusion forming multi-tooth cutting tool were obtained.

This paper introduces in detail the whole process of resin replacement of heavy water purification system in a reactor reconstruction project in Algeria, including old resin discharge, pipeline cleaning, new resin filling, new resin deuterization, water quality detection, heavy water storage and continuous operation of the system. By sorting out deuterization data and tracking and analyzing the water quality detection results, it is considered that the resin deuterization process of the heavy water purification system of a reactor is smooth. After deuterization, the effluent concentrations of the three resin columns of the heavy water purification system meet the operation requirements. The whole deuterization process tries to save precious high concentration heavy water for Algeria. After deuterization, the resin column is connected to the heavy water purification system. After continuous operation and sampling detection, it is determined that the purification effect is ideal and the pH value is not affected. The resin of the heavy water purification system is successfully replaced and can be put into use. At the same time, aiming at some problems in the deuterization process, this paper analyzes the causes in detail, summarizes the experience and lessons, and gives optimization suggestions and precautions in the deuterization process.

In the process of wood surface processing, it is easy to cause safety accident. Therefore, it is very necessary to find a new and clean processing method instead. In this paper, the laser automatic processing method is used instead of manual work, exploring the ablation of milled wood surfaces with nanosecond pulse laser. Four commonly used kinds of wood were selected, and milled separately in three different directions. The generation mechanism of micro burrs was analyzed under different working conditions. Then, a laser ablation experimental platform was established, and used to ablate the milling-induced burrs on the four kinds of wood. The ablated surfaces were observed under a scanning electron microscope (SEM). Based on the observations, the interaction between laser and surface burrs was investigated, and laser ablation deburring was modelled on ABAQUS. On this basis, the authors discussed how laser ablation deburring is affected by multiple laser parameters. The results show that cross-grain milling leads to more burrs on wood surface than parallel-to-grain milling and against-grain milling; for nanosecond laser ablation of wood surface burrs, the ablation efficiency and ablated surface quality could be optimized, when the output power falls between 300 mJ and 400 mJ; when the other parameters of the laser remain unchanged, there exists an optimal power density that helps to remove the surface burrs, without greatly affecting the nearby areas. The research results shed important new light on the deburring of wood products with the aid of pulse laser. Finally, it is proved that the mode of laser machining instead of traditional manual operation is feasible.

Hepatitis B virus (HBV) specifically infects hepatocytes, which can cause progressive liver fibrosis and a significantly increased risk of liver cancer. Multiple studies indicated host genetic, virological, and immunological factors could affect the HBV infection. However, the underlying mechanism involved in HBV infection remained unclear. Based on the analysis of gene expression data of 124 HBV patients (GEO accession: GSE84044), molecular subgroups of patients infected with hepatitis B virus were identified in this study, including C1, C2, and C3 groups. The age, fiber, degree of chemical and inflammation, and gene expression difference were also compared among the three sampling groups. Furthermore, the liver index was calculated using 93 liver-specific genes. The liver-specific gene expression in different molecular subgroups of HBV patients was thoroughly analyzed and then was compared with fibrosis and inflammation levels. Results showed that the C2 group was the youngest and the C3 group had the highest degree of fibrosis and inflammation. Enrichment analysis showed that metabolism-related pathways were mainly expressed in the C1 and C2 groups, and inflammation-related pathways and proteoglycans in cancer were highly expressed in the C1 and C3 groups. The liver index was higher in the C2 group than in the C1 and C3 groups, and it was the lowest in the C3 group. Macrophage M1/M2 and neutrophils were significantly different in the three groups. M1 was mainly abundant in the C3 group, and M2 and neutrophils were mainly abundant in the C2 group. This study provides novel information to understand the mechanisms of HBV infection in chronic hepatitis B (CHB) patients.

Herein, hierarchical WO3 microflowers with tailored oxygen vacancies are newly fabricated by a facile chemical bath deposition integrating H2-reduction route and exhibit a remarkably boosted activity toward visible-light-driven photocatalytic dye degradation, such as that of rhodamine B and methyl orange. The origin of the remarkably boosted activity can be readily ascribed to the integrated factors of the unique hierarchical microflowers and oxygen vacancies that contribute to the enhanced visible-light absorbance, the narrowed band gap and the reduced photoelectron–hole recombination ability. In addition, this photocatalyst also presents an excellent recycling performance due to its robust hierarchical structure and stable crystal phase, showing significant potential for future applications. It is anticipated that this work can shed a bright light on developing highly efficient photocatalysts toward visible-light-driven photocatalytic pollutant cleaning.

Selective conversion of aromatic alcohols to value-added chemicals is becoming an emerging research hotspot in heterogeneous photocatalysis, but its critical challenge is how to construct highly efficient photocatalysts. Herein, mesoporous (001)-TiO2 nanocrystals with tailored Ti3+ and surface oxygen vacancies have been fabricated by a facile hydrothermal route, showing remarkably boosted photoactivity for selective conversion of aromatic alcohols to carbonyl compounds in water medium under visible-light irradiation. Results attest that the remarkably boosted photoactivity was mainly correlated with the strong synergetic effect of exposed (001) facets, Ti3+ self-doping, and surface oxygen vacancies, leading to the enhanced reactant (aromatic alcohols and O2) activation via the high surface energy of (001) facets, the improved visible-light absorbance via the intrinsic band gap narrowing, and the escalated photoelectron–hole separation efficiency via Ti3+ and surface oxygen vacancies acting as electron sinks. Meanwhile, a plausible photocatalytic mechanism for selective conversion of aromatic alcohols to carbonyl compounds has been elucidated in detail based on active species identified by capture experiments. It is hoped that this work can deliver some new insights into the rational design of highly efficient photocatalysts applied in future green organic selective transformation reactions.

This paper is aimed at investigating the problem of mixed time/event-triggered finite-time non-fragile filtering for nonlinear networked control systems with delay. First, a fuzzy nonlinear networked control system model is established by interval type-2 (IT2) Takagi-Sugeno (T-S) fuzzy model, the designed non-fragile filter resolves the filter parameter uncertainties and uses different membership functions from the IT2 T-S fuzzy model. Second, a novel mixed time/event-triggered transmission mechanism is proposed, which decreases the waste of network resources. Next, Bernoulli random variables are used to describe the cases of random switching mixed time/event-triggered transmission mechanism. Then, the error filtering system is designed by considering a Lyapunov function and a sufficient condition of finite-time boundedness. In addition, the existence conditions for the finite-time non-fragile filter are given by the linear matrix inequalities (LMIs). Finally, two simulation results are presented to prove the effectiveness of the obtained method.

The modelling problem of nonlinear control system is studied, and a higher generality nonlinear U model is established. Based on the nonlinear U model, RBF neural network and PD parallel control algorithm are proposed. The difference between the control input value and the output value of the neural network is taken as the learning target by using the online learning ability of the neural network. The gradient descent method is used to adjust the PD output value, and ultimately track the ideal output. The Newton iterative algorithm is used to complete the transformation of the nonlinear model, and the nonlinear characteristic of the plant is reduced without loss of modelling precision, consequently, the control performance of the system is improved. The simulation results show that RBF neural network and PD parallel control system can control the nonlinear system. Moreover, the control system with Newton iteration can improve the control effect and anti-interference performance of the system.

The overall objective of this study is to design the nonlinear U-model-based radial basis function neural network model reference adaptive control system, through research into a class of complex time-varying nonlinear plants. First, the ideal nonlinear plant is adopted as the reference model and transformed into the U-model representation. In the process, the authors establish the corresponding relationship between the degrees of the reference nonlinear model and the controlled nonlinear plants, and carry out research into the corresponding coefficient relationship between the reference nonlinear model and the controlled nonlinear plants. Also, the impact of the adjusting amplitude and tracking speed of the model on the system control accuracy is analyzed. Then, according to the learning error index of the neural network, the paper designs the adaptive algorithm of the radial basis function neural network, and trains the network by the error variety. With the weight coefficients and network parameters automatically updated and the adaptive controller adjusted, the output of controlled nonlinear plants can track the ideal output completely. The simulation results show that the model reference adaptive control system based on RBF neural network has better control effect than the nonlinear U-model adaptive control system based on the gradient descent method.

An increasing number of studies have supported the critical regulatory actions of long noncoding RNAs (lncRNAs) in osteosarcoma (OS). However, the detailed roles of adipogenesis regulatory factor-antisense RNA 1 (ADIRF-AS1) in OS have not been comprehensively described. Hence, we first detected ADIRF-AS1 expression in OS and evaluated its clinical significance. Functional experiments were then performed to determine the modulatory role of ADIRF-AS1 in OS progression. ADIRF-AS1 was found to be overexpressed in OS, and the overall survival of patients with OS who had high ADIRF-AS1 levels was shorter than that of those with low levels. ADIRF-AS1 knockdown led to restricted proliferation, migration, and invasiveness of OS cells and increased apoptosis. Additionally, ADIRF-AS1 downregulation impeded tumor growth in vivo. Mechanistically, ADIRF-AS1 acted as a competitive endogenous RNA for microRNA-761 (miR-761) that siphoned miR-761 away from its target, namely insulin receptor substrate 1 (IRS1), leading to IRS1 overexpression. Rescue experiments showed that low levels of miR-761 or restoration of IRS1 could neutralize the effects of ADIRF-AS1 ablation in OS cells. In summary, ADIRF-AS1 exacerbates the oncogenicity of the OS cells by targeting the miR-761/IRS1 axis. Our findings may aid in the advancement of lncRNA-directed therapeutics for OS.

The important functions of long non-coding RNAs in the malignancy of non-small cell lung cancer (NSCLC) has been increasingly highlighted. However, whether LINC01748 functions in a crucial regulatory role still requires further research. The aim of the present study was to investigate the biological roles of LINC01748 in NSCLC. Furthermore, different experiments were utilized to investigate the mechanism of action of LINC01748 in 2 NSCLC cell lines. Reverse transcription-quantitative PCR was used to measure mRNA expression levels. Cell Counting Kit-8 assay, flow cytometry analysis and Transwell and Matrigel assays were also used to analyze, cell viability, apoptosis, and migration and invasion, respectively. A tumor xenograft model was used for in vivo experiments. RNA immunoprecipitation experiments, luciferase reporter assays and rescue experiments were used to investigate the mechanisms involved. Data from The Cancer Genome Atlas dataset and patients recruited into the present study showed that LINC01748 was overexpressed in NSCLC. Patients with high LINC01748 mRNA expression level had shorter overall survival rate compared with that in patients with low LINC01748 mRNA expression level. Then, knockdown of LINC01748 mRNA expression level reduced cell proliferation, migration and invasion, but increased cell apoptosis in vitro. Knockdown of LINC01748 also reduced tumor growth in vivo. Mechanistically, LINC01748 could act as a competing endogenous (ce)RNA to sponge microRNA(miR)-520a-5p, to increase the expression level of the target gene, high mobility group AT-hook 1 (HMGA1) in the NSCLC cell lines. Furthermore, rescue experiments illustrated that the functions exerted by LINC01748 knockdown were negated by miR-520a-5p inhibition or HMGA1 overexpression. In summary, LINC01748 acted as a ceRNA by sponging miR-520a-5p, leading to HMGA1 overexpression, thus increasing the aggressiveness of the NSCLC cells. Accordingly, targeting the LINC01748/miR-520a-5p/HMGA1 pathway may benefit NSCLC therapy.

Exploration algorithms based on the Boustrophedon path seldom consider the impacts of a robot turning at corners on the exploration time. This paper proposes the Forecast-Island and Bidding A*-Euclidean Selecting Boustrophedon Coordination (FIBA*ESBC) algorithm to calculate the turning time at corners in the overall exploration time and introduces a method to estimate the walking time in the Boustrophedon paths in order to determine the directions for path execution. Typically, in bidding-based exploration tasks, the cost is the Euclidean distance between the current position of the robot and the target point. When there is an obstacle between two points, the cost is set to infinity. Therefore, the selected target point is sometimes not optimal. The FIBA*ESBC algorithm is based on the exploration cost of a combination of the Euclidean distance and A* algorithm walking path, which can effectively solve this problem. Because the bidding is based on a greedy algorithm, the robot has a small unexplored island in the later exploration stage; therefore, full exploration is not possible or requires a long time with several repeated paths. The FIBA*ESBC algorithm prioritizes the exploration and estimation of hidden and existing unexplored islands. It can realize complete exploration and decrease the exploration time. Through simulation experiments conducted using Gazebo and RViz, the feasibility of the FIBA*ESBC algorithm is verified. Moreover, a simulation experiment is conducted in MATLAB for comparison with other algorithms. The analysis of the experimental data shows that the proposed algorithm has a relatively short exploration time.

Compared with other materials, high-volume fraction aluminum-based silicon carbide composites (hereinafter referred to as SiCp/Al) have many advantages, including high strength, small change in the expansion coefficient due to temperature, high wear resistance, high corrosion resistance, high fatigue resistance, low density, good dimensional stability, and thermal conductivity. SiCp/Al composites have been widely used in aerospace, ordnance, transportation service, precision instruments, and in many other fields. In this study, the ABAQUS/explicit large-scale finite element analysis platform was used to simulate the milling process of SiCp/Al composites. By changing the parameters of the tool angle, milling depth, and milling speed, the influence of these parameters on the cutting force, cutting temperature, cutting stress, and cutting chips was studied. Optimization of the parameters was based on the above change rules to obtain the best processing combination of parameters. Then, the causes of surface machining defects, such as deep pits, shallow pits, and bulges, were simulated and discussed. Finally, the best cutting parameters obtained through simulation analysis was the tool rake angle γ0 = 5°, tool clearance angle α0 = 5°, corner radius r = 0.4 mm, milling depth ap = 50 mm, and milling speed vc = 300 m/min. The optimal combination of milling parameters provides a theoretical basis for subsequent cutting.

This paper is aimed at investigating the problem of mixed-triggered filter design for interval type-2 (IT2) fuzzy nonlinear Markovian jump systems (MJSs) with randomly occurring packet dropouts. First, an IT2 fuzzy nonlinear MJSs model with parameter uncertainties is established by using IT2 fuzzy model, and the fuzzy filter is designed with different premise variables. Second, a novel mixed-triggered scheme is addressed, which can reduce the needless waste of network resources. Then, two Bernoulli stochastic variables are employed, one to randomly switch the different modes of the mixed-triggered scheme, the other to describe the randomly occurring packet dropouts. Next, in order to ensure that IT2 fuzzy filtering error system is asymptotically stable, sufficient conditions are presented. Moreover, the existence conditions for the fuzzy filter are given by the linear matrix inequalities. Finally, simulation results are given to verify the validity of the proposed method.

AIM To investigate the association between work-family conflicts and career development with resilience among nurses. BACKGROUND Nurses tend to have high levels of work-family conflict. Resilience may affect their individual career development, the stability of the nursing team and the quality of nursing care. METHODS A cross-sectional survey using correlational design was conducted in mainland China. Data were collected using demographic and career development questionnaire, work-family conflict and resilience scale. RESULTS A total of 70,932 nurses were included. The total score for work-family conflict was relatively high (38.37 ± 12.82). Work-family conflict of nurses had a significant negative correlation with career development (r = -0.35, p

Photocatalytic hydrogenation of nitrobenzenes to anilines has become a rising research hotspot in the field of heterogeneous catalysis; however, its bottleneck is the design of high-activity photocatalysts. In this work, mesoporous (101)-TiO2 nanocrystals with tailored Ti3+ and surface oxygen vacancies have been prepared through a combined facile hydrothermal and post-reduction approach, and exhibit significantly enhanced activity for photocatalytic hydrogenation of nitrobenzenes to anilines in water medium under visible-light irradiation. Experimental results show that the significantly enhanced activity of the prepared photocatalysts is mainly attributed to the strong synergetic effect of the exposed (101) facets, Ti3+ self-doping, and surface oxygen vacancies, distinctly resulting in enhanced photoelectron-enrichment on the (101) facet by the accumulated reduction sites, an improved visible-light harvesting ability by energy band gap narrowing, and a boosted photoelectron–hole separation ability by Ti3+ and surface oxygen vacancies acting as electron sinks. Meanwhile, a plausible reaction mechanism for photocatalytic hydrogenation of nitrobenzenes to anilines has been proposed and elucidated in detail based on active species capturing experiments. It's expected that this work can stimulate increasing interest in designing high-activity photocatalysts for future green and sustainable organic synthesis.

Inner staminodes are widespread in Magnoliales and present in Anaxagorea and Xylopia, but were lost in the other genera of Annonaceae and have no counterparts in derived angiosperms. The coexistence of normal stamens, modified stamens and inner staminodes in Anaxagorea javanica is essential to understand the homology and pollination function of the inner staminodes. Anaxagorea javanica was subjected to an anatomical study by light and scanning electron microscopy, and the chemistry of secretions was evaluated by an amino acid analyser. Inner staminodes have a secretory apex, but do not have thecae. They bend towards either tepals or carpels at different floral stages, and function as a physical barrier preventing autogamy and promoting outcrossing. At the pistillate phase, the exudates from the inner staminodes have high concentration of amino acid, and provide attraction to pollinating insects; while abundant proline was only detected in stigmas exudates, and supply for pollen germination. Modified stamens have a secretory apex and one or two thecae, which are as long as or shorter than that of the normal stamens. As transitional structures, modified stamens imply a possible degeneration progress from normal stamens to inner staminodes: generating a secretory apex first, shortening of the thecae length next and then followed by the loss of thecae. The presence of modified stamens together with the floral vasculature and ontogeny imply that the inner staminodes are homologous with stamens., Inner staminodes are widespread in Magnoliales and present in Anaxagorea and Xylopia, but were lost in the other genera of Annonaceae and have no counterparts in derived angiosperms. This paper demonstrates that the inner staminodes are homologous with stamens in Anaxagorea by documenting the existence of modified stamens with reduced thecae and secretory structures, and similar vasculature and phyllotactic continuity of stamens and staminodes as well. This paper also provides original data on floral phenology and chemical exudates of the staminodes and stigmas, which confirm the function of the staminodes during pollination in preventing autogamy.

While the single ant colony algorithm and the fish swarm algorithm have many advantages, they also have various shortcomings. After analyzing the advantages and disadvantages of the ant colony algorithm and the fish swarm algorithm, this paper uses the complementary principle of the two algorithms to effectively fuse the two population intelligent algorithms. The improved swarm intelligence algorithm is applied to the well-considered protein folding prediction problem, and the simplified protein structure Toy model is verified, and the ideal results are obtained. The improved algorithm enhances the search ability, and the computational efficiency is greatly improved, ensuring the accuracy of the operation.

Simulated annealing algorithm (SA) has the performance of jumping out of local extremum and good global convergence. This algorithm can solve many multidimensional problems well. Based on the basic principle, process and characteristics of the simulated annealing algorithm, this paper analyzed and discussed the influencing factors of the algorithm, and emphatically analyzed the selection principles of the simulation annealing algorithm’s Metropolis criteria and cooling schedule parameters. In this paper, the annealing process of the object is simulated to solve the problem, that is, the value of the parameter is adjusted, and the appropriate parameter value is finally selected. It is of great significance to the selection of the parameter of the simulated annealing algorithm in solving the multi-dimensional problem.

Constructing visible-light-driven photocatalysts with outstanding performances for selective alcohol oxidation has become a research frontier in the field of heterogeneous photocatalysis. Herein, simultaneously generating Bi quantum dot and oxygen vacancy on Bi2MoO6 nanosheets, facilely achieved through a hydrothermal combining post-reduction route, has been developed to catalyze selective alcohol oxidation in D.I. H2O medium via visible-light-driven heterogeneous photocatalysis, actually presenting the remarkably boosted photoactivity and excellent reusability. Experimental results reveal that the remarkably boosted photoactivity can be intrinsically credited to the synergetic effect of oxygen vacancy and Bi quantum dot, strikingly leading to the narrowed band gap, the improved visible-light absorbance as well as the escalated photocharge separation capability. Impressively, its excellent reusability can be mainly correlated with Bi quantum dot strongly interacting with robust Bi2MoO6 nanosheet that not only inhibits the structural collapse of Bi2MoO6 nanosheet but also the leaching of Bi quantum dot, demonstrating its promising potential in future sustainable organic synthesis.

Pollen of angiosperms may be either binucleate or trinucleate at maturity. According to Schurhoff–Brewbaker law, the binucleate state is pleisomorphic occuring in about 70% of all angiosperms, while the trinucleate state is advanced occurring in about 30% of the angiosperms. The derivation of trinucleate pollen from binucleate pollen is irreversible, thus trinucleate or mixed pollen was considered uncommon in early lineage. In the present work, using conventional paraffin section method, the coexistence of both binucleate and trinucleate pollen in the same intact anther were observed in Mitrephora macclurei, a species belonging to the eumagnoliid family Annonaceae. The increasing number of plants with trinucleate or mixed pollen discovered in early lineages, as well as climatic introduced changes in nuclear number challenge analyses of ancestral state and evolution of pollen nuclear number in angiosperms.

In basal angiosperms, there are several types of permanent tetrad but their formation pattern remains elusive. Pseuduvaria trimera has five types of tetrads and is the species with the most abundant tetrad types in Annonaceae. In order to interpret the formation pattern of different tetrad types, pollen development was investigated from the microspore mother cell stage to the bicellular pollen stage and the ultrastructure of pollen wall in the five tetrad types using light microscopy, transmission electron microscopy, and confocal laser scanning microscopy. Both successive and intermediate cytokinesis were observed within the same anther. The nucleus location of the microspores together with cytokinesis determine the number and the spatial arrangement of callose plates, and further have an effect on the tetrad types. The anthers with or without septation and the arrangement of microsporocytes might be also related to the tetrad type. The individual pollen grains within the tetrads are connected with each other by crosswall cohesion and cytoplasmic channels at localized points in the proximal walls. The various types of tetrads, cytokinesis, and cohesion in P. trimera reflect the high diversity in pollen development, which enhances the dramatic variety in pollen morphology in this family. Our observations of the development of tetrads provided some new insights for interpreting the factors influencing the types of tetrads, and reported the existence of a cytoplasmic channel in Annonaceae for the first time.