evolutionary mechanism
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2021 ◽  
Vol 9 (12) ◽  
pp. 1338
Author(s):  
Hongran Chen ◽  
Mengyang Zhai ◽  
Lei Xue

The recession of a coast can destabilize coastal cliffs. The stability of a cliff is controlled by a rock bridge. Identifying the volume-expansion point of rock bridges is crucial to assess cliff stability, but currently there are few identifying methods. Using a numerical analytical tool, we investigate the acoustic emission characteristics during shear tests on rock bridges. Acoustic emission events with a high energy level, i.e., characteristic events which occur at the volume-expansion point of rock bridges, can indicate this point. The characteristic events, the mainshock (the maximum event corresponding to rock-bridge rupture), and the smaller events between them constitute a special activity pattern, as the micro-seismicity during the evolutionary process of a coastal cliff collapse in Mesnil-Val, NW France showed. This pattern arises in rock bridges with different mechanical properties and geometry, or under different loading conditions. Although the energy level of characteristic events and mainshocks changes with the variation of the conditions, the difference of their energy level is approximately constant. The spatial distribution of characteristic events and mainshocks can indicate the location of rock bridges. These findings help to better understand the evolutionary mechanism of collapses and provide guidelines for monitoring the stability of coastal cliffs.


Author(s):  
Robert N. Spengler

AbstractOver the past decade, niche construction theory (NCT) has been one of the fastest-growing theories or scholarly approaches in the social sciences, especially within archaeology. It was proposed in the biological sciences 25 years ago and is often referred to as a neglected evolutionary mechanism. Given its rapid acceptance by the archaeological community, it is important that scholars consider how it is being applied and look for discrepancies between applications of the concept. Many critical discussions of NCT have already been published, but most of them are in biology journals and may be overlooked by scholars in the social sciences. In this manuscript, my goal is to synthesis the criticisms of NCT, better allowing archaeologists to independently evaluate its usefulness. I focus on the claims of novelty and differences between NCT and other approaches to conceptualizing anthropogenic ecosystem impacts and culture-evolution feedbacks. I argue that the diverse concepts currently included in the wide-reaching purview of NCT are not new, but the terminology is and may be useful to some scholars. If proponents of the concept are able to unify their ideas, it may serve a descriptive function, but given that lack of a testable explanatory mechanism, it does not have a clear heuristic function.


2021 ◽  
Author(s):  
Fulai Liu ◽  
Jialiang Xu ◽  
Lijie Zhang ◽  
Ruiyan Du ◽  
Zhibo Su ◽  
...  

Abstract Intrusion detection is a crucial technology in the communication network security field. In this paper, a dynamic evolutionary sparse neural network (DESNN) is proposed for intrusion detection, named as DESNN algorithm. Firstly, an ensemble neural network model is constructed, which is processed by a dynamic pruning rule and further divided into advantage subnetworks and disadvantage subnetworks. The dynamic pruning rule can effectively reduce the subnetworks weight parameters, thereby increasing the speed of the subnetworks intrusion detection. Then considering the subnetworks performance loss caused by the dynamic pruning rule, a novel evolutionary mechanism is proposed to optimize the training process of the disadvantage subnetworks. The weight of the disadvantage subnetworks approach the weight of the advantage subnetworks by the evolutionary mechanism, such that the performance of the ensemble neural network can be improved. Finally, an optimal subnetwork is selected from the ensemble neural network, which is used to detect multiple types of intrusion. Experiments show that the proposed DESNN algorithm improves intrusion detection speed without causing significant performance loss compare with other fully-connected neural network models.


Entropy ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 681
Author(s):  
Peng Niu ◽  
Jianhua Zhu ◽  
Yanming Sun

To explore the cooperative evolutionary mechanism among top management support, employees’ technical ability, and informatization performance in the process of the “integration of informatization and industrialization (IOII)” in manufacturing enterprises, this study established a three-dimensional dynamic model of informatization development, obtained the model parameters by the expert scoring method of case companies, and analyzed the time series of the dynamic model. After adjusting those parameters of the evolutionary process that do not meet the expectations of the enterprise, combined with management practice, the dynamic system is finally stable at the expected value. For a special state in the evolutionary process, the maximum Lyapunov exponent is used to identify the chaotic characteristics of the system, and a linear controller is designed to manage and control the chaotic system so that it evolves toward the expected value. The results of the case analysis verify the rationality of the model and the effectiveness of the control method, reveal the internal evolutionary mechanism of the informatization development of manufacturing enterprises, and explain the influence of chaos on enterprise management so as to help managers to use and control chaos.


mBio ◽  
2021 ◽  
Vol 12 (3) ◽  
Author(s):  
Sankhya Bommana ◽  
Naraporn Somboonna ◽  
Gracie Richards ◽  
Maryam Tarazkar ◽  
Deborah Dean

ABSTRACT The obligate intracellular pathogen Chlamydia trachomatis (Ct) is the leading cause of bacterial sexually transmitted infections and blindness globally. To date, Ct urogenital strains are considered tryptophan prototrophs, utilizing indole for tryptophan synthesis within a closed-conformation tetramer comprised of two α (TrpA)- and two β (TrpB)-subunits. In contrast, ocular strains are auxotrophs due to mutations in TrpA, relying on host tryptophan pools for survival. It has been speculated that there is strong selective pressure for urogenital strains to maintain a functional operon. Here, we performed genetic, phylogenetic, and novel functional modeling analyses of 595 geographically diverse Ct ocular, urethral, vaginal, and rectal strains with complete operon sequences. We found that ocular and urogenital, but not lymphogranuloma venereum, TrpA-coding sequences were under positive selection. However, vaginal and urethral strains exhibited greater nucleotide diversity and a higher ratio of nonsynonymous to synonymous substitutions [Pi(a)/Pi(s)] than ocular strains, suggesting a more rapid evolution of beneficial mutations. We also identified nonsynonymous amino acid changes for an ocular isolate with a urogenital backbone in the intergenic region between TrpR and TrpB at the exact binding site for YtgR—the only known iron-dependent transcription factor in Chlamydia—indicating that selective pressure has disabled the response to fluctuating iron levels. In silico effects on protein stability, ligand-binding affinity, and tryptophan repressor (TrpR) affinity for single-stranded DNA (ssDNA) measured by calculating free energy changes (ΔΔG) between Ct reference and mutant tryptophan operon proteins were also analyzed. We found that tryptophan synthase function was likely suboptimal compared to other bacterial tryptophan prototrophs and that a diversity of urogenital strain mutations rendered the synthase nonfunctional or inefficient. The novel mutations identified here affected active sites in an orthosteric manner but also hindered α- and β-subunit allosteric interactions from distant sites, reducing efficiency of the tryptophan synthase. Importantly, strains with mutant proteins were inclined toward energy conservation by exhibiting an altered affinity for their respective ligands compared to reference strains, indicating greater fitness. This is not surprising as l-tryptophan is one of the most energetically costly amino acids to synthesize. Mutations in the tryptophan repressor gene (trpR) among urogenital strains were similarly detrimental to function. Our findings indicate that urogenital strains are evolving more rapidly than previously recognized with mutations that impact tryptophan operon function in a manner that is energetically beneficial, providing a novel host-pathogen evolutionary mechanism for intracellular survival. IMPORTANCE Chlamydia trachomatis (Ct) is a major global public health concern causing sexually transmitted and ocular infections affecting over 130 million and 260 million people, respectively. Sequelae include infertility, preterm birth, ectopic pregnancy, and blindness. Ct relies on available host tryptophan pools and/or substrates to synthesize tryptophan to survive. Urogenital strains synthesize tryptophan from indole using their intact tryptophan synthase (TS). Ocular strains contain a trpA frameshift mutation that encodes a truncated TrpA with loss of TS function. We found that TS function is likely suboptimal compared to other tryptophan prototrophs and that urogenital stains contain diverse mutations that render TS nonfunctional/inefficient, evolve more rapidly than previously recognized, and impact operon function in a manner that is energetically beneficial, providing an alternative host-pathogen evolutionary mechanism for intracellular survival. Our research has broad scientific appeal since our approach can be applied to other bacteria that may explain evolution/survival in host-pathogen interactions.


2021 ◽  
Author(s):  
Kazutaka Katoh ◽  
Daron M. Standley

Abstract The ability to predict emerging variants of SARS-CoV-2 would be of enormous value, as it would enable proactive design of vaccines in advance of such emergence. Based on molecular evolutionary analysis of the S protein, we found a significant correspondence in the location of amino acid substitutions between SARS-CoV-2 variants recently emerging and their relatives that infected bat and pangolin before the pandemic. This observation suggests that a limited number of sites in this protein are repeatedly substituted in different lineages of this group of viruses. It follows, therefore, that the sites of future emerging mutations in SARS-CoV-2 can be predicted by analyzing their relatives (outgroups) that have infected non-human hosts. We discuss a possible evolutionary mechanism behind these substitutions and provide a list of frequently substituted sites that potentially include future emerging variants in SARS-CoV-2.


2021 ◽  
Author(s):  
Kazutaka Katoh ◽  
Daron M. Standley

Abstract The ability to predict emerging variants of SARS-CoV-2 would be of enormous value, as it would enable proactive design of vaccines in advance of such emergence. Based on molecular evolutionary analysis of the S protein, we found a significant correspondence in the location of amino acid substitutions between SARS-CoV-2 variants recently emerging and their relatives that infected bat and pangolin before the pandemic. This observation suggests that a limited number of sites in this protein are repeatedly substituted in different lineages of this group of viruses. It follows, therefore, that the sites of future emerging mutations in SARS-CoV-2 can be predicted by analyzing their relatives (outgroups) that have infected non-human hosts. We discuss a possible evolutionary mechanism behind these substitutions and provide a list of frequently substituted sites that potentially include future emerging variants in SARS-CoV-2.


2021 ◽  
Author(s):  
Kazutaka Katoh ◽  
Daron M. Standley

Abstract The ability to predict emerging variants of SARS-CoV-2 would be of enormous value, as it would enable proactive design of vaccines in advance of such emergence. Based on molecular evolutionary analysis of S protein, we found a significant correspondence in the location of amino acid substitutions between SARS-CoV-2 variants recently emerging and their relatives that infected bat and pangolin before the pandemic. This observation suggests that a limited number of sites in this protein are repeatedly substituted in independent lineages of this group of viruses. It follows, therefore, that the sites of future emerging mutations in SARS-CoV-2 can be predicted by analyzing their relatives (outgroups) that have infected non-human hosts. We discuss a possible evolutionary mechanism behind these substitutions and provide a list of frequently substituted sites that potentially include future emerging variants in SARS-CoV-2.


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