Study on Sludge and Dissolved Oxygen Distribution in a Full-Scale A2/O Oxidation Ditch

The distribution of velocity, sludge, and dissolved oxygen in a full-scale anaerobic-anoxic-oxic (A2/O) oxidation ditch was numerically simulated under three rotation speed scenarios. The viscosity and settling rate of activated sludge were defined through a user-defined function (UDF), and the sludge phase was calculated using the mixture multiphase flow model. Dissolved oxygen (DO) was set as a user-defined source (UDS) and its generation and consumption rates were defined with UDFs. The relationship between velocity and sludge concentration was found to be contradictory, with dead zones leading to large sludge concentrations at the bottom of the oxidation ditch (OD), but not at the middle-curved wall of the anoxic pool. The flow rate of the reflux slot and aerator oxygenation rate were checked and correlated with DO concentrations in the anaerobic pool. The majority of the large sludge concentrations were concentrated in the biological selection pool and these remained constant with bed height. With reduced propeller and agitator rotation speed, the sludge concentrations reduced in the biological selection pool, but increased in the anaerobic and anoxic pools.

Bionic design of the tower for wind turbine

The study obtains a methodology for the bionic design of the tower for wind turbines. To verify the rationality of the biological selection, the Analytic Hierarchy Procedure (AHP) is applied to calculate the similarity between the bamboo and the tower. Creatively, a bionic bamboo tower (BBT) is presented, which is equipped with four reinforcement ribs and five flanges. Further, finite element analysis is employed to comparatively investigate the performance of the BBT and the original tower (OT) in the static and dynamic. Through the investigation, it is suggested that the maximum deformation and maximum stress can be reduced by 5.93 and 13.75% of the BBT. Moreover, this approach results in 3% and 1.1% increase respectively in the First two natural frequencies and overall stability.

Proust's Genies: In Search of Lost Time and Population Biology

Whether identified as “genies,” “little men,” or simply “les moi,” a vast horde of personified mental faculties populates In Search of Lost Time, responsible for behaviors too instantaneous or too ingrained to come under conscious control. Representing automatic neural subroutines as self-interested beings allows Proust to apply the principles of biological selection to these psychological entities, imagining the mind as an ecosystem in which great personal upheavals—for instance, Marcel's loss of Albertine—figure as extinction events that wipe out large populations of narrowly specialized, slow-to-adapt “genies.” Since genies are optimized for highly specific micro-environments, the same “species” of genie may form in any two individuals who share such a micro-environment, with this indifference to the boundaries of the person making it possible for a shared genie-type to define an ad hoc social category: homosexuals, snobs, members of the Guermantes set. In this essay, I unpack Search's model of the mind as a population of simple homunculi and explore its effect on Proust's understanding of interpersonal collectives, from intellectual coteries to social classes. The construct of the genie, I suggest, not only allows Proust to suture together sub-individual and supra-individual scales of analysis but also enables a model of change—both psychological and historical—that is neither simply agentic nor simply deterministic. Rather, the shifting demographics of mental homunculi constitute a quantitative, probabilistic, and nonsychronous form of change, creating new adaptive niches while permitting the partial survival of prior forms of life.

Comprehensive Essentiality Analysis of the Mycobacterium tuberculosis Genome via Saturating Transposon Mutagenesis

ABSTRACT For decades, identifying the regions of a bacterial chromosome that are necessary for viability has relied on mapping integration sites in libraries of random transposon mutants to find loci that are unable to sustain insertion. To date, these studies have analyzed subsaturated libraries, necessitating the application of statistical methods to estimate the likelihood that a gap in transposon coverage is the result of biological selection and not the stochasticity of insertion. As a result, the essentiality of many genomic features, particularly small ones, could not be reliably assessed. We sought to overcome this limitation by creating a completely saturated transposon library in Mycobacterium tuberculosis . In assessing the composition of this highly saturated library by deep sequencing, we discovered that a previously unknown sequence bias of the Himar1 element rendered approximately 9% of potential TA dinucleotide insertion sites less permissible for insertion. We used a hidden Markov model of essentiality that accounted for this unanticipated bias, allowing us to confidently evaluate the essentiality of features that contained as few as 2 TA sites, including open reading frames (ORF), experimentally identified noncoding RNAs, methylation sites, and promoters. In addition, several essential regions that did not correspond to known features were identified, suggesting uncharacterized functions that are necessary for growth. This work provides an authoritative catalog of essential regions of the M. tuberculosis genome and a statistical framework for applying saturating mutagenesis to other bacteria. IMPORTANCE Sequencing of transposon-insertion mutant libraries has become a widely used tool for probing the functions of genes under various conditions. The Himar1 transposon is generally believed to insert with equal probabilities at all TA dinucleotides, and therefore its absence in a mutant library is taken to indicate biological selection against the corresponding mutant. Through sequencing of a saturated Himar1 library, we found evidence that TA dinucleotides are not equally permissive for insertion. The insertion bias was observed in multiple prokaryotes and influences the statistical interpretation of transposon insertion (TnSeq) data and characterization of essential genomic regions. Using these insights, we analyzed a fully saturated TnSeq library for M. tuberculosis , enabling us to generate a comprehensive catalog of in vitro essentiality, including ORFs smaller than those found in any previous study, small (noncoding) RNAs (sRNAs), promoters, and other genomic features.

Entropy and Selection: Life as an Adaptation for Universe Replication

Natural selection is the strongest known antientropic process in the universe when operating at the biological level and may also operate at the cosmological level. Consideration of how biological natural selection creates adaptations may illuminate the consequences and significance of cosmological natural selection. An organismal trait is more likely to constitute an adaptation if characterized by more improbable complex order, and such order is the hallmark of biological selection. If the same is true of traits created by selection in general, then the more improbably ordered something is (i.e., the lower its entropy), the more likely it is to be a biological or cosmological adaptation. By this logic, intelligent life (as the least-entropic known entity) is more likely than black holes or anything else to be an adaptation designed by cosmological natural selection. This view contrasts with Smolin’s suggestion that black holes are an adaptation designed by cosmological natural selection and that life is the by-product of selection for black holes. Selection may be the main or only ultimate antientropic process in the universe/multiverse; that is, much or all observed order may ultimately be the product or by-product of biological and cosmological selection.