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Liaoning terminal and Beijing railway station are significant architectural heritage sites along the Peking–Mukden Railway. Their architectural styles do not only embody their cultural value but also serve as their carriers. This study explores the relationship between the architectural styles of these two stations and their geometric characteristics to uncover the origins and underlying principles of their styles, thereby contributing to their preservation and renovation. By analyzing the geometric systems, order of plans and elevations, and the visual complexity of their elevations, the study provides valuable insights. The classical attributes of these stations are manifested through the use of geometric proportion systems with a considerable fractal dimension, demonstrating continuity across different scales. Conversely, their modernity and national style are reflected in the intricate elevation elements, which exhibit varying fractal dimensions across different elevation layers. [ABSTRACT FROM AUTHOR]

Colony formation is a crucial trait that enhances the ability of Microcystis to withstand the complex and ever-changing aquatic environment. However, the cellular response within a colony has not been extensively investigated. This research gap can be attributed to the difficulty of isolating individual cells within the colony. In this study, we employed a colonial strain of Microcystis and devised a preliminary method framework known as the 'onion peeling method' to analyze the cell characteristics within different regions of the colony. The method demonstrated high efficiency by successfully isolating 34.8% of cells from the colony while causing minimal damage. Additionally, we conducted an application study using this method to examine the influence of external nutrient availability. The findings indicate that the peripheral Microcystis cells located near the colony's surface were more vulnerable to a decrease in external nutrient availability, resulting in a reduced frequency of cell division (from 0.27 to 0.11 – 0.12). On the other hand, the internal cells showed more stability, which could be attributed to the presence of the intra-colony phycosphere. The findings of the application study indicate the significant role of colony formation in minimizing the impact of adverse environmental conditions on internal cells. This could be one of the factors contributing to the prolonged occurrence of Microcystis blooms. Furthermore, our method framework study suggests a broader application potential, as comparing the cellular characteristics of Microcystis from different intra-colony regions may help uncover biological or ecological strategies. [ABSTRACT FROM AUTHOR]

Equivariant Euler characteristics are important numerical homotopy invariants for objects with group actions. They have deep connections with many other areas like modular representation theory and chromatic homotopy theory. They are also computable, especially for combinatorial objects like partition posets, buildings associated with finite groups of Lie types, etc. In this article, we make new contributions to concrete computations by determining the equivariant Euler characteristics for all subgroup complexes of symmetric groups Σ n when n is prime, twice a prime, or a power of two and several variants. There are two basic approaches to calculating equivariant Euler characteristics. One is based on a recursion formula and generating functions, and another on analyzing the fixed points of abelian subgroups. In this article, we adopt the second approach since the fixed points of abelian subgroups are simple in this case. [ABSTRACT FROM AUTHOR]

Colony formation of cyanobacteria is crucial for the formation of surface blooms in lakes. However, the underlying mechanisms of colony formation involving in physiological and cell surface characteristics remain to not well be established. Six cyanobacterial Microcystis strains (including both unicellular and colonial ones) were employed to estimate the influences of their physiological traits and the composition of extracellular polymeric substances (EPS) on colony or aggregate formation. Results show that raising the number of the photosynthetic reaction center and light-harvesting antenna in the PSII and reducing the growth rate were the major physiological strategies of Microcystis to produce excess EPS enhancing colony formation. Tightly bound EPS (T-EPS) was responsible for colony formation, which approximately accounted for 50% of the total amount of EPS. Five fluorescent components (protein-, tryptophan-, and tyrosine-like components and two humic-like components) were found in the T-EPS, although the amounts of these components varied with strains. Importantly, colonial strains contained much higher tyrosine-like substances than unicellular ones. We suggest that tyrosine-like substances might serve as a crosslinking agent to connect other polymers in EPS (e.g., proteins or polysaccharides) for colony formation. Our findings identified key physiological traits and chemical components of EPS for colony formation in Microcystis, which can contribute to a better understanding on the formation of Microcystis blooms. [ABSTRACT FROM AUTHOR]

Co-combustion characteristics and interactions of municipal solid waste (MSW) and low-rank coal semi-coke (LCSC) in O2/CO2 or air atmosphere are investigated by the thermogravimetric method, including analyses of thermodynamic, kinetic parameters and reaction mechanism function. Results indicated that addition of MSW and higher oxygen concentration improve the co-combustion performance of blends. There are three distinct peaks for co-combustion of blends in air atmosphere, while only two peaks in 30O2/70CO2 atmosphere. It indicates that the presence of CO2 in oxy-fuel atmosphere is conducive to semi-char burnout. Interactions of MSW and LCSC mainly occur between 260 °C and 650 °C, and the synergetic interaction is very obvious around the second peak region of combustion process. The average activation energies Ea show an upward trend with the increase in oxygen concentration, and the minimum value of Ea is obtained when the blend ratio of MSW is 50% which might be an optimal option for co-combustion of blends. Activation energy, enthalpy changes, Gibbs function and entropy changes for 50MSW50LCSC in 30O2/70CO2 atmosphere are 140.86 kJ mol−1, 138.33 kJ mol−1, 161.94 kJ mol−1 and − 41.44 J mol−1 K−1, respectively. In O2/CO2 atmospheres, F6 and F1 functions are more suitable to describe the starting and subsequent process of entail reaction. The results can provide a theoretical and practical guidance for the harmless disposal and resource utilization of MSW and LCSC. [ABSTRACT FROM AUTHOR]

Extracellular polysaccharide (EPS) can be distinguished into soluble or bound types and significantly contributes to colony formation in Microcystis. Depending on the binding strength with cells, the bilayer structure of bound EPS contains loosely or tightly bound EPS (LB-EPS or TB-EPS) and their roles in shaping the size and tightness of Microcystis colonies deserve further investigation. In this study, the influences of two types of bound EPS on the size and tightness of Microcystis colonies were investigated after a series of pretreatment to obtain LB-EPS retaining or stripped samples. Results showed that cells with LB-EPS formed large and loose colonies. Furthermore, the ratios of LB-EPS to TB-EPS, which indicate the size and tightness of the colonies, were higher in the retaining groups than in the stripped groups. Our findings also provide evidence that calcium enrichment is conducive to colony formation in Microcystis. This study provides new insights into the formation and enlargement of Microcystis colonies, which contributes to a better understanding on the role of EPS in Microcystis aggregation and morphology changes. [ABSTRACT FROM AUTHOR]

In lakes, suspended inorganic particles and dissolved substance are able to absorb or scatter different light wavelengths, leading to the changes of underwater light spectra which are highly related to the water quality. In turn, such changes could form environmental filtering for phytoplankton community to select particular algal populations via intensive competition for light resources. As an example, eutrophic lakes where underwater light spectra changed dramatically have a result of cyanobacterial blooms. In this study, in order to test the effect of light spectrum on growth and competition of green algae and cyanobacteria, Chlorella pyrenoidosa (a common green alga) and Microcystis aeruginosa (a bloom-forming cyanobacterium) grew and competed under three light colors: white (400–700 nm), red (620–700 nm), and blue (410–490 nm) light. Mono- and co-cultured systems were designed and population dynamics of the two species were monitored. The Lotka-Volterra model was used to quantify interspecific competition. Moreover, their photosynthetic activities were measured in mono-cultures. Results showed that in mono-cultures, red light was more favorable for M. aeruginosa, while blue light promoted the growth of C. pyrenoidosa. In co-cultures, M. aeruginosa won in red light and white light, while C. pyrenoidosa dominated under blue light. Light color mainly affected the absorption flux of reaction center (ABS/RC) in photosynthetic system II (PSII) and its potential photosynthetic capacity (Fv/Fm). Fv/Fm of M. aeruginosa in red light (or C. pyrenoidosa in blue light) was significantly enhanced. This study revealed that light color showed a significant influence on interspecific competition between green algae and cyanobacteria, which offers new insights into the dominance establishment and bloom formation of Microcystis. [ABSTRACT FROM AUTHOR]

Pico-cyanobacteria and micro-cyanobacteria coexist ubiquitously in many lakes. Differences in cell size and abilities to utilize nutrients may influence their distribution patterns. In this study, Synechococcus sp. and Microcystis aeruginosa were chosen as pico- and micro-cyanobacteria, respectively. Gradient phosphorus treatments (0.002, 0.01, 0.05, and 0.25 mg P L−1) were designed in mono- and co-cultures. Growth curves were recorded and fitted by the Monod equation. Moreover, the interspecific competition was analyzed by the Lotka-Volterra model. When mono-cultured in lower P conditions (≤ 0.01 mg P L−1), Synechococcus sp. obtained much higher biomass than M. aeruginosa. But, M. aeruginosa grew faster than Synechococcus sp. in higher P groups (≥ 0.05 mg P L−1) (p < 0.05). Synechococcus sp. has abilities to thrive in low-phosphorus environments, whereas M. aeruginosa favored high-phosphorus conditions. In co-cultures, Synechococcus sp. strongly inhibited M. aeruginosa at each P treatment. [ABSTRACT FROM AUTHOR]

Ultrasound can be used to induce cell resonance and cavitation to inhibit cyanobacterial growth, but it can also lead to increase in dissolved nutrients because of cell disruption. This study investigated the process from cell inactivation to disruption of Microcystis aeruginosa. Algal cells were sonicated (at 35 kHz) under various intensities and durations. Results showed that chlorophyll a content and Fv/Fm values decreased slightly within the first 5 min. Superoxide dismutase activity was stimulated and its peak value appeared at the fifth minute. After 20 min, considerable number of ruptured cells were observed and the concentrations of dissolved nitrogen and phosphorus increased rapidly. Finally, ammonia and nitrate merely composed a small portion of dissolved nitrogen. This study demonstrated that excessive ultrasound treatment can significantly rupture algal cells and lead to the release of cellular inclusions, which may cause ecological issues or public health problems. Based on our findings, ultrasonic intensity controlled at 0.035 W/mL and applied for a duration of 20 min delivers the optimal result in effectively inhibiting physiological activities of Microcystis aeruginosa without marked cell disruption. This will ultimately help to achieve algal control, while conserving energy and preserving the environment and human health. [ABSTRACT FROM AUTHOR]

Ultrasonication has drawn an increasing attention as one of cell disruption methods for extracting cellular compounds or controlling algal blooms. However, the effects of biological and physical properties of microalgae on cell disruption were not well understood. In this work, cell disruption of six microalgae, namely, Chlamydomonas reinhardtii, Chlorella pyrenoidosa, Microcystis aeruginosa (three strains: PCC 7806, FACHB 469, and FACHB 1343), and Synechococcus elongatus, was compared mutually based on their characteristics induced by a low-frequency ultrasound (35 kHz, 0.043 W mL). Results showed that the most sensitive strain was C. reinhardtii which has a hydroxyproline-rich-glycoproteins cell wall and a larger cell size (normally 10 μm in diameter). More than 80% of the cells of C. reinhardtii were ruptured after sonication for 5 min. In comparison, C. pyrenoidosa, a cellulose-rich-wall algal species with a medium size of 4-6 μm, and M. aeruginosa FACHB 1343, a peptidoglycan-wall species with a smaller average size of 2.3 μm, were highly resistant to ultrasound. Only 7.5 and 7.7% of cell disruption were achieved for C. pyrenoidosa and M. aeruginosa FACHB 1343, respectively, when they were sonicated for 60 min. Declumping effect was dominant in these strains. This suggested that cellulose-rich-wall algal species might be much more resistant than hydroxyproline-rich glycoproteins, and peptidoglycan-wall species to sonication. It also revealed that the larger cell size was more susceptible to sonication the cell would be. This research provides useful insights into choosing the low-cost microalgae for extraction or controlling specific microalgal blooms in water systems using ultrasound. [ABSTRACT FROM AUTHOR]

This paper significantly extends previous studies to the transition regime by employing the second-order slip boundary conditions. A simple analytical model with second-order slip boundary conditions for a normalized Poiseuille number is proposed. The model can be applied to either rarefied gas flows or apparent liquid slip flows. The developed simple models can be used to predict the Poiseuille number, mass flow rate, tangential momentum accommodation coefficient, pressure distribution of gaseous flow in noncircular microchannels and nanochannels by the research community for the practical engineering design of microchannels and nanochannels. The developed second-order models are preferable since the difficulty and 'investment' is negligible compared with the cost of alternative methods such as molecular simulations or solutions of Boltzmann equation. Navier-Stokes equations with second-order slip models can be used to predict quantities of engineering interest such as the Poiseuille number, tangential momentum accommodation coefficient, mass flow rate, pressure distribution, and pressure drop beyond its typically acknowledged limit of application. The appropriate or effective second-order slip coefficients include the contribution of the Knudsen layers in order to capture the complete solution of the Boltzmann equation for the Poiseuille number, mass flow rate, and pressure distribution. It could be reasonable that various researchers proposed different second-order slip coefficients because the values are naturally different in different Knudsen number regimes. It is analytically shown that the Knudsen's minimum can be predicted with the second-order model and the Knudsen value of the occurrence of Knudsen's minimum depends on inlet and outlet pressure ratio. The compressibility and rarefaction effects on mass flow rate and the curvature of the pressure distribution by employing first-order and second-order slip flow models are analyzed and compared. The condition of linear pressure distribution is given. [ABSTRACT FROM AUTHOR]

Microscale fluid dynamics has received intensive interest due to the emergence of Micro-Electro-Mechanical Systems (MEMS) technology. When the mean free path of the gas is comparable to the channel’s characteristic dimension, the continuum assumption is no longer valid and a velocity slip may occur at the duct walls. Non-circular cross sections are common channel shapes that can be produced by microfabrication. The non-circular microchannels have extensive practical applications in MEMS. Slip flow in non-circular microchannels has been examined and a simple model is proposed to predict the friction factor and Reynolds product fRe for slip flow in most non-circular microchannels. Through the selection of a characteristic length scale, the square root of cross-sectional area, the effect of duct shape has been minimized. The developed model has an accuracy of 10% for most common duct shapes. The developed model may be used to predict mass flow rate and pressure distribution of slip flow in non-circular microchannels. [ABSTRACT FROM AUTHOR]

Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body. [ABSTRACT FROM AUTHOR]