Discrete Ornstein-Uhlenbeck process in a stationary dynamic enviroment

The thesis is devoted to the study of solutions to the following linear recursion: \beq X_{n+1}=\gamma X_n+ \xi_n, \feq where $\gamma \in (0,1)$ is a constant and (\xi_n)_{n\in\zz} is a stationary and ergodic sequence of normal variables with \emph{random} means and variances. More precisely, we assume that \beq \xi_n=\mu_n+\sigma_n\veps_n, \feq where (\veps)_{n\in\zz} is an i.i.d. sequence of standard normal variables and (\mu_n,\sigma_n)_{n\in\zz} is a stationary and ergodic process independent of (\veps_n)_{n\in\zz}, which serves as an exogenous dynamic environment for the model. This is an example of a so called SV (stands for stochastic variance or stochastic volatility) time-series model. We refer to the stationary solution of this recursion as a discrete Ornstein-Uhlenbeck process in a stationary dynamic environment. \par The solution to the above recursion is well understood in the classical case, when $\xi_n$ form an i.i.d. sequence. When the pairs mean and variance form a two-component finite-state Markov process, the recursion can be thought as a discrete-time analogue of the Langevin equation with regime switches, a continuous-time model of a type which is widely used in econometrics to analyze financial time series. \par In this thesis we mostly focus on the study of general features, common for all solutions to the recursion with the innovation/error term $\xi_n$ modulated as above by a random environment $(\mu_n,\sigma_n),$ regardless the distribution of the environment. In particular, we study asymptotic behavior of the solution when $\gamma$ approaches $1.$ In addition, we investigate the asymptotic behavior of the extreme values $M_n=\max_{1\leq k\leq n} X_k$ and the partial sums $S_n=\sum_{k=1}^n X_k.$ The case of Markov-dependent environments will be studied in more detail elsewhere. \par The existence of general patterns in the long-term behavior of $X_n,$ independent of a particular choice of the environment, is a manifestation of the universality of the underlying mathematical framework. It turns out that the setup allows for a great flexibility in modeling yet maintaining tractability, even when is considered in its full generality. We thus believe that the model is of interest from both theoretical as well as practical points of views; in particular, for modeling financial time series

Pragmatic Communication in Multi-Agent Collaborative Perception

Collaborative perception allows each agent to enhance its perceptual abilities by exchanging messages with others. It inherently results in a trade-off between perception ability and communication costs. Previous works transmit complete full-frame high-dimensional feature maps among agents, resulting in substantial communication costs. To promote communication efficiency, we propose only transmitting the information needed for the collaborator's downstream task. This pragmatic communication strategy focuses on three key aspects: i) pragmatic message selection, which selects task-critical parts from the complete data, resulting in spatially and temporally sparse feature vectors; ii) pragmatic message representation, which achieves pragmatic approximation of high-dimensional feature vectors with a task-adaptive dictionary, enabling communicating with integer indices; iii) pragmatic collaborator selection, which identifies beneficial collaborators, pruning unnecessary communication links. Following this strategy, we first formulate a mathematical optimization framework for the perception-communication trade-off and then propose PragComm, a multi-agent collaborative perception system with two key components: i) single-agent detection and tracking and ii) pragmatic collaboration. The proposed PragComm promotes pragmatic communication and adapts to a wide range of communication conditions. We evaluate PragComm for both collaborative 3D object detection and tracking tasks in both real-world, V2V4Real, and simulation datasets, OPV2V and V2X-SIM2.0. PragComm consistently outperforms previous methods with more than 32.7K times lower communication volume on OPV2V. Code is available at github.com/PhyllisH/PragComm.Comment: 18 page

Comparative metagenomic analysis of microbial community compositions and functions in cage aquaculture and its nearby non-aquaculture environments

In the context of burgeoning global aquaculture, its environmental repercussions, particularly in marine ecosystems, have gained significant attentions. Cage aquaculture, a prominent method, has been observed to significantly influence marine environments by discharging substantial amounts of organic materials and pollutants. It is also one of the important reasons for water eutrophication. This study investigated the impacts of cage aquaculture on microbial diversity and functional potential using metagenomics. Specifically, a comparison was made of the physicochemical indicators and microbial diversity between three grouper aquaculture cage nets in Lingshui Xincun Port and three nearby non-aquaculture area surface waters. We found that compared to non-aquaculture areas, the eutrophication indicators in aquaculture environments significantly increased, and the abundances of Vibrio and Pseudoalteromonas in aquaculture environments significantly rose. Additionally, microbial functional genes related to carbon, nitrogen, and sulfur metabolisms were also found to be significantly affected by aquaculture activities. The correlation analysis between microbial populations and environmental factors revealed that the abundances of most microbial taxa showed positive correlations with dissolved inorganic nitrogen, soluble reactive phosphorus, NH4+, and negative correlations with dissolved oxygen. Overall, this study elucidated the significant impacts of aquaculture-induced eutrophication on the diversity and functions of planktonic bacterial communities

Phycobiliproteins: Molecular Structure, Production, Applications, and Prospects

Phycobiliproteins (PBPs) are the main component of light-harvesting complexes in cyanobacteria and red algae. In addition to their important role in photosynthesis, PBPs have many potential applications in foods, cosmetics, medical diagnosis and treatment of diseases. However, basic researches and technological innovations are urgently needed for exploring those potentials, such as structure and function, their biosynthesis as well as downstream purification. For medical use and application, mechanisms underlying their therapeutic effects must be elucidated. Focusing on these issues, this article gives a critical review on the current status on PBPs, including their structures and functions, preparation processes and applications. In addition, key technical challenges and possible solutions are prospected

Čimbenik prirodne obnove vrste Platycladus orientalis (L.) Franco u Guilinu, Kina

Cypress (Platycladus orientalis (L.) Franco) is one of the important evergreen trees for afforestation in barren mountains, soil consolidation, and water conservation, but natural regeneration of cypress is complex and slow. An understanding of the influence mechanism of the natural regeneration of cypresses is essential for elevating survival and regeneration. This study aimed to clarify the relationship between stand factors, environmental factors, and regeneration of cypress plantations. A total of 42 cypress sample plots in Guilin, China, were selected to evaluate the impact of various stand factors and environmental factors on the regeneration of cypresses using survey statistics and Pearson and Spearmanrank correlation analysis. In this study, cypress has the highest frequency and density of regeneration among all the seedlings in the 18 surveyed forests, but the height structure of cypress seedlings distributes in uneven mode and mainly Grade I (height < 30 cm) seedlings. Low-density herbs and high-density moss mulching had a directly positive effect on the number of cypress regeneration seedlings. Larger soil stone content and gap area can promote cypress regeneration, which is appropriate for cypresses in the seedling stage. In conclusion, timely weeding, proper soil loosening, and improving light transmittance contribute to promoting the regeneration of cypresses.Obična azijska tuja (Platycladus orientalis (L.) Franco) je jedno od važnih zimzelenih stabala za pošumljavanje u neplodnim planinama, za konsolidaciju tla i očuvanje vode, ali prirodna regeneracija obične azijske tuje je složena i spora. Razumijevanje mehanizma utjecaja na prirodnu regeneraciju obične azijske tuje bitno je za poticanje preživljavanja i regeneraciju. Cilj ovog istraživanja je objasniti odnos između šumskih sastojina, okolišnih čimbenika i regeneracije nasada obične azijske tuje. Ukupno 42 uzorka čempresa u Guilinu, Kina, odabrane su za procjenu utjecaja različitih čimbenika sastojine i okolišnih čimbenika na regeneraciju čempresa korištenjem statistike ankete i korelacijske analize Pearson i Spearmanrank. U ovoj studiji, obična azijska tuja ima najveću učestalost i gustoću regeneracije među svim sadnicama ( 18 ) u istraživanoj šumi, ali je visinska struktura sadnica obične azijske tuje raspoređena neravnomjerno, a radi se uglavnom o sadnicama I klase (visina < 30 cm). Bilje niske gustoće i malčiranje mahovine velike gustoće, imali su izravan pozitivan učinak na broj sadnica za regeneraciju obične azijske tuje. Veći sadržaj kamena u tlu i opustošenih površina mogu potaknuti regeneraciju obične azijske tuje, ali je to prikladnije za obične azijske tuje u fazi sadnice. Zaključno, pravodobno plijevljenje korova, pravilno rahljenje tla i poboljšanje propusnosti svjetla mogli bi potaknuti regeneraciju obične azijske tuje

Novel genetic reassortants in H9N2 influenza A viruses and their diverse pathogenicity to mice

<p>Abstract</p> <p>Background</p> <p>H9N2 influenza A viruses have undergone extensive reassortments in different host species, and could lead to the epidemics or pandemics with the potential emergence of novel viruses.</p> <p>Methods</p> <p>To understand the genetic and pathogenic features of early and current circulating H9N2 viruses, 15 representative H9N2 viruses isolated from diseased chickens in northern China between 1998 and 2010 were characterized and compared with all Chinese H9N2 viruses available in the NCBI database. Then, the representative viruses of different genotypes were selected to study the pathogenicity in mice with the aim to investigate the adaptation and the potential pathogenicity of the novel H9N2 reassortants to mammals.</p> <p>Results</p> <p>Our results demonstrated that most of the 15 isolates were reassortants and generated four novel genotypes (B62-B65), which incorporated the gene segments from Eurasian H9N2 lineage, North American H9N2 branch, and H5N1 viruses. It was noteworthy that the newly identified genotype B65 has been prevalent in China since 2007, and more importantly, different H9N2 influenza viruses displayed a diverse pathogenicity to mice. The isolates of the 2008-2010 epidemic (genotypes B55 and B65) were lowly infectious, while two representative viruses of genotypes B0 and G2 isolated from the late 1990s were highly pathogenic to mice. In addition, Ck/SD/LY-1/08 (genotype 63, containing H5N1-like NP and PA genes) was able to replicate well in mouse lungs with high virus titers but caused mild clinical signs.</p> <p>Conclusion</p> <p>Several lines of evidence indicated that the H9N2 influenza viruses constantly change their genetics and pathogenicity. Thus, the genetic evolution of H9N2 viruses and their pathogenicity to mammals should be closely monitored to prevent the emergence of novel pandemic viruses.</p

An application of Pixel Interval Down-sampling (PID) for dense tiny microorganism counting on environmental microorganism images

This paper proposes a novel pixel interval down-sampling network (PID-Net) for dense tiny objects (yeast cells) counting tasks with higher accuracy. The PID-Net is an end-to-end CNN model with encoder to decoder architecture. The pixel interval down-sampling operations are concatenated with max-pooling operations to combine the sparse and dense features. It addresses the limitation of contour conglutination of dense objects while counting. Evaluation was done using classical segmentation metrics (Dice, Jaccard, Hausdorff distance) as well as counting metrics. Experimental result shows that the proposed PID-Net has the best performance and potential for dense tiny objects counting tasks, which achieves 96.97% counting accuracy on the dataset with 2448 yeast cell images. By comparing with the state-of-the-art approaches like Attention U-Net, Swin U-Net and Trans U-Net, the proposed PID-Net can segment the dense tiny objects with clearer boundaries and fewer incorrect debris, which shows the great potential of PID-Net in the task of accurate counting tasks