Performance analysis of typical linear augmented observers for a class of MIMO systems with nonlinear uncertainty.

To estimate the states and the uncertainties for multi-input-multi-output (MIMO) systems is significant in control engineering. The paper investigates the estimating performance of a widely-used linear augmented observer (LAO) by quantitatively analyzing the biased term of estimation error, which generalizes the previous studies. Then the necessary and sufficient condition for unbiased estimation of LAO is thoroughly discussed. More importantly, by investigating the observability of MIMO uncertain systems, the paper proves that the estimation of LAO is unbiased if and only if the states and the uncertainties of MIMO uncertain systems are observable. The presented theoretical analysis can help practitioners evaluate the feasibility of estimating the specific uncertainties via LAO in practical systems. Finally, even if the estimation of LAO is biased, the design procedure of extended state observer is presented, which offers the unbiased estimation of total disturbance and the derivatives of output.

The source and transport of bioaerosols in the air: A review.

Recent pandemic outbreak of the corona-virus disease 2019 (COVID-19) has raised widespread concerns about the importance of the bioaerosols. They are atmospheric aerosol particles of biological origins, mainly including bacteria, fungi, viruses, pollen, and cell debris. Bioaerosols can exert a substantial impact on ecosystems, climate change, air quality, and public health. Here, we review several relevant topics on bioaerosols, including sampling and detection techniques, characterization, effects on health and air quality, and control methods. However, very few studies have focused on the source apportionment and transport of bioaerosols. The knowledge of the sources and transport pathways of bioaerosols is essential for a comprehensive understanding of the role microorganisms play in the atmosphere and control the spread of epidemic diseases associated with them. Therefore, this review comprehensively summarizes the up to date progress on the source characteristics, source identification, and diffusion and transport process of bioaerosols. We intercompare three types of diffusion and transport models, with a special emphasis on a widely used mathematical model. This review also highlights the main factors affecting the source emission and transport process, such as biogeographic regions, land-use types, and environmental factors. Finally, this review outlines future perspectives on bioaerosols.

Vertical variations in the concentration and community structure of airborne microbes in PM2.5.

With the recent rapid development of urbanization, severe air pollution events frequently occur in China. Subsequently, variations of bioaerosols during air pollution events have attracted increasing attention in recent years. However, most published studies on bioaerosols mainly focus on the characteristics of airborne bacteria and fungi at a certain height near the ground surface. The vertical variations in microbial aerosols at different heights are not well understood. In this study, PM2.5 samples at three heights (1.5 m, 100 m and 229.5 m) were collected from September 2019 to January 2020 in Xi'an, China. The samples were then analyzed by a fluorescence staining and high-throughput sequencing to explore the vertical variations in the concentration and community structure of the airborne bacteria. The results show that the microbial concentration in PM2.5 decreased with increasing height on polluted days, while there was no significant difference at different heights on non-polluted days (p > 0.05). The bacterial community structures were similar at different heights on polluted days; however, on non-polluted days, the bacterial community structure at 229.5 m was significantly different from that at the other heights. Importantly, meteorological factors had more significant effects on the bacterial community at 229.5 m than at 1.5 m and 100 m. The present results can improve the understanding of vertical distribution of bioaerosols and their diffusion process.

[Characteristics and Sources of Microbial Aerosols in Urban and Mountainous Areas in Autumn and Winter in Xi'an, China].

To explore the bioaerosol composition characteristics and sources in urban areas and mountains, three sample sites were selected in urban (urban, suburban) and southern mountainous areas in Xi'an, and air, soil, and leaf samples were simultaneously collected. The fungi and bacteria community structures at different sampling sites were analyzed through a high-throughput sequencing method, and their spatio-temporal variations were also examined. Moreover, a source track technique was used to identify the source of microorganisms in the air. The results showed that the fungi and bacteria at different sampling sites were significantly different, indicating that the geographical location has a significant influence on the community structure of microorganisms in the air. In winter, more potential fungal pathogens and bacterial pathogens were detected in urban areas with high relative abundance and diversity. In addition, the results showed that the main local source of fungi and bacteria was the leaf surface, of which the contribution rate of bacteria in the air fine particles was up to (55±30)%. This study can provide a scientific basis for understanding the characteristics of microbial pollution in the atmosphere, and for air environment quality evaluation and disease prevention in China.

Temporal-spatial variations of fungal composition in PM2.5 and source tracking of airborne fungi in mountainous and urban regions.

Fungi are ubiquitous in air and their composition is potentially important for human health. Exposure to fungal allergens has been considered as a significant risk factor due to the prevalence and severity of asthma in humans. However, temporal-spatial variations and potential sources of airborne fungi aerosol have been poorly understood. In this study, 48 PM2.5 samples were collected at two sampling sites in Xi'an from April 2018 to January 2019. High-throughput sequencing technology was used to determine the diversity and abundance of fungal composition in all samples. Microbial samples were also collected from leaf-surface and soil to identify the potential sources of fungal aerosols. Results showed that the species richness of fungi in summer and autumn inclined to be higher than that in spring and winter in mountainous and urban regions. Airborne fungal species richness and diversity at Mt. Qinling sampling site were significantly higher compared to Yanta urban sampling site, except in winter. These variations in fungal composition were significantly related to season and location. The influence of atmospheric pollutants (PM2.5, ozone, sulfur dioxide and carbon monoxide) on the richness and diversity of airborne fungal composition was higher than meteorological factors (temperature, relative humidity and wind speed). Moreover, it was observed that the leaf-surface was the primary local source of airborne fungi during all seasons at both sampling sites. Back trajectories arriving at both sampling sites showed that a considerable part of airborne fungi might have come from other regions by medium or long-range airflow. This study will provide an important reference for studying the source and temporal-spatial variations of fungal aerosols and further provide basic background data for human health exposure assessment.

Calmodulin binds to maize lipid transfer protein and modulates its lipids binding ability.

Although plant non-specific lipid transfer proteins (ns-LTPs) are characterized by their ability to bind and transfer a broad range of hydrophobic ligands in vitro, their biological functions in vivo remain unclear. Recently, it has been proposed that ns-LTPs may play a key role in plant defense mechanisms, particularly during the induction of systemic acquired resistance, however, very little is known about the regulation in this process. We report that the binding of maize non-specific lipid transfer protein (Zm-LTP) to calmodulin (CaM) is in a calcium-independent manner. To better understand the interaction mechanism between Zm-LTP and CaM, the CaM-binding site of Zm-LTP was mapped to the region of amino acids 46-60. Point mutations indicate that four amino acid residues, R46, R47, K54 and R58, in this region are crucial for binding. Furthermore, we tested the effects of CaM on the lipid-binding activity of Zm-LTP in the presence of Ca(2+), EGTA, N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide and trifluoperazine respectively. We also investigated the structural features of CaM-binding motifs in LTPs from different species and strong differences were observed. Taken together, our results suggest that the interaction with CaM could be a common feature of plant LTPs. The identification and characterization of CaM-binding domain of LTPs should provide new insights into the mechanism by which the physiological functions of LTPs are regulated.

[The effects of calmodulin on the lipid-binding activity of CaM-binding protein-10 and maize non-specific lipid transfer protein].

Fluorescence-marked lipid binding experiment shows that CaMBP-10 has typical lipid binding feature of non-specific lipid transfer protein (nsLTP). We have compared the effects of calmodulin (CaM) on the lipid-binding activity of CaMBP-10 and maize nsLTP. Different influences were found in the presence of either Ca(2+) or EGTA. W-7 and TFP could abolish the influence of CaM. Therefore, it is suggested that CaM could interact specifically with both CaMBP-10 and maize nsLTP. Probably, there are different CaM regulatory mechanisms between CaMBP-10 and maize nsLTP.

[Cloning and expression of cDNA for maize nonspecific lipid transfer protein as well as calmodulin-binding activity analysis of the expression product].

Maize nonspecific lipid transfer protein (Zm-nsLTP) was cloned and expressed to investigate its CaM-binding activity. The cDNA of Zm-nsLTP was amplified using RT-PCR (Fig.1), and then inserted into the vector pET32a(+). The recombinant vector pET-Zm-nsLTP was expressed in E. coli BL21(DE3)trxB(-). Results of CaM-gel overlay assays (Fig.2) and CaM-sepharose pull-down experiments (Fig.3) indicated that recombinant Zm-nsLTP was bound to CaM in a Ca(2+)-independent manner, which is in accordance with the way that CaMBP-10 and Arabidopsis non-specific lipid transfer protein-1 (At-nsLTP1) are bound to CaM. The CaM-binding domain in Zm-nsLTP was mapped to the region of 47-60 amino acids (Fig.3), and online sequence analysis using Predict Protein program predicted that it has a BAA structure (Fig.4,5).