Search Results (31)

Variations in damper configuration strategies have a direct impact on the seismic damage patterns of long-span deck-type concrete-filled steel tube (CFST) arch bridges. This study developed an analysis and evaluation framework to identify the damage category, state, and progression sequence of structural components. The framework aims to investigate the influence of viscous dampers on the seismic response and damage patterns of long-span deck-type CFST arch bridges under near-fault pulse-like ground motions. The effects of different viscous damper configuration strategies and design parameters on seismic responses of long-span deck-type CFST arch bridges were systematically investigated, and the preferred configuration and parameter set were identified. The influence of preferred viscous damper configurations on seismic damage patterns of long-span deck-type CFST arch bridges was systematically analyzed through the established analysis and evaluation frameworks. The results indicate that a relatively optimal reduction in bridge response can be achieved when viscous dampers are simultaneously installed at both the abutments and the approach piers. Minimum seismic responses were attained at a damping exponent α = 0.2 and damping coefficient C = 6000 kN/(m/s), demonstrating stability in mitigating vibration effects on arch rings and bearings. In the absence of damper implementation, the lower chord arch foot section is most likely to experience in-plane bending failure. The piers, influenced by the coupling effect between the spandrel construction and the main arch ring, are more susceptible to damage as their height decreases. Additionally, the end bearings are more prone to failure compared to the central-span bearings. Implementation of the preferred damper configuration strategy maintains essentially consistent sequences in seismic-induced damage patterns of the bridge, but the peak ground motion intensity causing damage to the main arch and spandrel structure is significantly increased. This strategy enhances the damage-initiation peak ground acceleration (PGA) for critical sections of the main arch, while concurrently reducing transverse and longitudinal bending moments in pier column sections. The proposed integrated analysis and evaluation framework has been validated for its applicability in capturing the seismic damage patterns of long-span deck-type CFST arch bridges. Full article

Urban parks are essential public resources that contribute significantly to residents’ well-being. However, disparities in the spatial distribution and social benefits of urban parks remain a pressing issue. This study focuses on the central urban area of Shanghai, a representative high-density megacity, and its findings hold significant reference value for similar cities, systematically evaluating urban park services from the perspectives of accessibility, spatial equity, and social equity. Leveraging multi-source big data and enhanced analytical methods, this study examines disparities and spatial mismatches in park services. By incorporating dynamic data, such as actual visitor attendance and residents’ travel preferences, and improving analytical models, such as an enhanced Gaussian two-step floating catchment area method and spatial lag regression models, this research significantly improves the accuracy and reliability of its findings. Key findings include (1) significant variations in accessibility exist across different types of parks, with regional and city parks offering better accessibility compared to pocket parks and community parks. (2) Park resources are unevenly distributed, with neighborhoods within the inner ring exhibiting relatively low overall accessibility. (3) A spatial mismatch is observed between park accessibility and housing prices, highlighting equity concerns. The dual spatial-social imbalance phenomenon reveals the prevalent contradiction in rapidly urbanizing areas where public service provision lags behind land development. Based on these results, this study proposes targeted recommendations for optimizing urban park layouts, including increasing the supply of small parks in inner-ring areas, enhancing the multifunctionality of parks, and strengthening policy support for disadvantaged communities. These findings contribute new theoretical insights into urban park equity and fine-grained governance while offering valuable references for urban planning and policymaking. Full article

In this study, novel focusing performances of high-numerical-aperture (NA) micro-Fresnel zone plates (FZPs) with selective occlusion are identified and investigated through numerical calculations based on vectorial angular spectrum (VAS) theory, and further rigorously validated using the finite-difference time-domain (FDTD) method. The central occlusion of a standard micro-FZP can significantly extend the depth of focus while keeping the lateral size of the focusing spot essentially unchanged. When a standard micro-FZP only retains two separated transparent rings and all other rings are obstructed, it will result in multi-focus phenomena; at the same time, the number of focal points is equal to the difference in number between the two separated transparent rings. Furthermore, a focusing light needle can be generated by combining the central occlusion and wavelength shift of a standard micro-FZP. This study not only provides new ideas for the design and optimization of micro-FZPs but also provides reference for the expansion of practical applications of FZPs. Full article

Pumiceous deposits, commonly found in volcanic regions such as the Ring of Fire and the Alpide Belt, pose significant engineering challenges due to the presence of highly crushable and compressible grains in their matrix. These deposits exhibit complex geotechnical characteristics and are frequently linked to natural events like landslides and earthquakes. Research in countries such as New Zealand, Japan, Indonesia, Italy, and Central and South America aims to better understand the mechanical behaviour of these materials. Key influencing factors include geological properties, microstructure, shearing characteristics, and the impact of particle breakage. Comparative studies have identified similarities in specific gravity, void ratio, particle size distribution, and shearing mechanisms across regions. However, notable differences appear when compared to hard-grained sands including higher void ratios, variations in relative density due to crushable grains, and increased angularity. Some responses of pumiceous deposits, such as strain softening, liquefaction resistance depending on gradation, and apparent cohesion from grain interlocking, mirror those of hard sands; however, particle crushing plays a crucial role in the behaviour. Accurate numerical modelling, which simulates crushing under different conditions, is essential for characterising pumiceous deposits in situ, providing engineers with a better understanding of these materials across diverse site conditions. Full article

In the fullerene cone HIV-1 capsid, the central channels of the hexameric and pentameric capsomers each contain a ring of arginine (Arg18) residues that perform essential roles in capsid assembly and function. In both the hexamer and pentamer, the Arg18 rings coordinate inositol hexakisphosphate, an assembly and stability factor for the capsid. Previously, it was shown that amino-acid substitutions of Arg18 can promote pentamer incorporation into capsid-like particles (CLPs) that spontaneously assemble in vitro under high-salt conditions. Here, we show that these Arg18 mutant CLPs contain a non-canonical pentamer conformation and distinct lattice characteristics that do not follow the fullerene geometry of retroviral capsids. The Arg18 mutant pentamers resemble the hexamer in intra-oligomeric contacts and form a unique tetramer-of-pentamers that allows for incorporation of an octahedral vertex with a cross-shaped opening in the hexagonal capsid lattice. Our findings highlight an unexpected degree of structural plasticity in HIV-1 capsid assembly. Full article

Tropical maar lakes are distinct ecosystems with unique ecological features. To comprehend, manage, and conserve these lakes, it is essential to understand their water sources, particularly groundwater, and the hydrogeochemical processes shaping their water chemistry. This research focuses on the maar lake Alchichica in central Mexico, known for harboring 18 new and endemic species and a ring of stromatolites. With groundwater discharge as the primary source, concerns arise over anthropic extraction impacts on water levels and stromatolite survival. Sampling six wells and one piezometer revealed major ion (Ca²⁺, Mg²⁺, K⁺, Na⁺, Cl⁻, HCO₃⁻, SO₄²⁻) and trace element (Fe, Al³⁺, SiO₂) concentrations. Geochemical evolution was explored through diagrams, geological sections, and inverse geochemical models using the PHREEQC code. Findings indicate groundwater evolving along controlled flow paths, and influencing chemical composition through water–rock interactions. The lake’s unique conditions, resulting from the mixing of two flows, enable stromatolite formation. Water level reduction appears unrelated to evaporation at the sampled sites, suggesting a need for a broader study in a larger area. Analyzing the maar lake’s hydrochemistry provides valuable insights into unique characteristics supporting high endemism in this ecosystem. This research enhances our understanding of groundwater’s geochemical processes and hydrogeochemical evolution in maar lakes, with potential applications worldwide. Full article

Tumor necrosis factor receptor-associated factors (TRAFs) are a protein family with a wide variety of roles and binding partners. Among them, TRAF6, a ubiquitin ligase, possesses unique receptor binding specificity and shows diverse functions in immune system regulation, cellular signaling, central nervous system, and tumor formation. TRAF6 consists of an N-terminal Really Interesting New Gene (RING) domain, multiple zinc fingers, and a C-terminal TRAF domain. TRAF6 is an important therapeutic target for various disorders and structural studies of this protein are crucial for the development of next-generation therapeutics. Here, we presented a TRAF6 N-terminal structure determined at the Turkish light source “Turkish DeLight” to be 3.2 Å resolution at cryogenic temperature (PDB ID: 8HZ2). This structure offers insight into the domain organization and zinc-binding, which are critical for protein function. Since the RING domain and the zinc fingers are key targets for TRAF6 therapeutics, structural insights are crucial for future research. Separately, we rationally designed numerous new compounds and performed molecular docking studies using this template (PDB ID:8HZ2). According to the results, 10 new compounds formed key interactions with essential residues and zinc ion in the N-terminal region of TRAF6. Molecular dynamic (MD) simulations were performed for 300 ns to evaluate the stability of three docked complexes (compounds 256, 322, and 489). Compounds 256 and 489 was found to possess favorable bindings with TRAF6. These new compounds also showed moderate to good pharmacokinetic profiles, making them potential future drug candidates as TRAF6 inhibitors. Full article

The expansion of renewable energy sources and sustainable infrastructures for the generation of electrical and thermal energies and fuels increasingly requires efforts to develop efficient technological solutions and holistically balanced systems to ensure a stable energy supply with high energy utilization. For investigating such systems, a research infrastructure was established within the nationally funded project Energy Lab 2.0 including essential components for generation, conversion and storage of different energy sources. One element includes a thermal energy storage (TES) system based on solid materials, which was supplemented by an electrically heated storage component. Hereby, the overall purpose is to efficiently generate and store high-temperature heat from electrical energy with high specific powers during the charging period and provide thermal energy during the discharging period. Today’s solutions focus on convective electrical heating elements, creating, however, two major challenges for large-scale systems: limited load gradients due to existing systemic inertias and limited operating temperatures of 700 °C in the MW scale. To overcome such restrictions, a novel electrically heated storage component with dual operating modes was developed. The central component of this solution is a ring-shaped honeycomb body based on an SiC ceramic with electrical heating registers on the inside and outside. This configuration allows, in storage operation, instantaneous direct heating of the honeycomb body via thermal radiation. At the end of systemic start-up procedures, an operational change toward a convective heating system takes place, whereby the high-temperature heat previously stored is transferred to downstream components. The simulation studies performed for such a component show, for both operating modes, high operating temperatures of over 800 °C with simultaneous high electrothermal efficiencies of up to 90%. Experimental investigations on a 100 kW scale at the DLR test facility HOTREG in Stuttgart confirmed the feasibility, performance and good agreement with simulation results for a selected honeycomb geometry with a mass of 181 kg. With its successful testing and good scalability, the developed component opens up high use case potentials in future Power-to-Heat-to-Power applications, particularly for Brayton process-based Carnot batteries and adiabatic compressed air energy storage systems. Full article

As the challenges of globalization and climate change intensify, the importance of urban resilience in city planning is becoming increasingly evident. To adapt to this trend, innovations and improvements are essential in traditional urban land-use patterns to better fulfill the requirements of resilient urban development. In this context, this study constructs an urban resilience evaluation index system from four perspectives: social resilience, engineering resilience, ecological resilience, and security resilience to evaluate the urban resilience of Changsha City. A thorough assessment of the resilience mechanisms in Changsha’s urban layout was conducted, employing the SD-FLUS model. A resilient urban scenario is also established to restrict the conversion of high-resilience land into other land types and to predict urban land-use structures under a resilience-oriented directive. The findings indicate that areas with high ecological and safety resilience in Changsha are primarily located in the western Weishan mountain system, along with eastern mountain systems like Jiuling, Lianyun, and Mufu, forming the “green veins”. The central areas are characterized by “blue veins”, mainly represented by rivers such as the Xiangjiang, Weishui, Longwanggang, Jinjiang, Liuyang, and Laodao. Within the central urban area, high-resilience regions are primarily distributed along a framework consisting of “one ring (the city’s three-ring line), two mains (Xiangjiang and Liuyang rivers), one heart (urban green core), and six wedges”, specifying various green corridors. Under the resilience-oriented scenario, the model predicts that by 2025, the total built-up area in Changsha will be 1416.79 km². Areas with high social and engineering resilience are mainly concentrated in the central urban areas of Changsha, as well as Ningxiang and Liuyang, aligning closely with the objectives of Changsha’s latest round of national spatial planning. The built-up area layout should complement Changsha’s topography and water systems, expanding in a wedge-like manner. Overall, Changsha’s planning has successfully integrated social, engineering, ecological, and safety resilience, enhancing its adaptability and long-term sustainability. This research proposes a land-use simulation method guided by the concept of urban resilience, providing valuable insights for resilience-oriented city planning in Changsha and other cities facing similar challenges. Full article

The degree of coordination between the supply and demand for urban green spaces serves as a vital metric for evaluating urban ecological development and the well-being of residents. An essential principle in assessing this coordination is the precise quantification of both the demand and supply of green spaces, as well as the differential representation of their spatiotemporal structures. This study utilizes the entropy weight method (EWM) and principal component analysis (PCA) to comprehensively measure supply indicators for green space quantity and quality in the central urban area of Shenyang, China. To establish reliable and quantifiable demand indicators, mobile signaling spatial-temporal data are corrected by incorporating static population cross-sectional data. The Gaussian two-step floating catchment area method (Ga2SFCA) is employed to calculate the accessibility of green spaces in each community with ArcGIS 10.2 software, while the Gini coefficient is utilized to assess the equity of green space distribution within the study area. This study employs location entropy to determine the levels of supply and demand for green spaces in each subdistrict. Furthermore, the priority of community-scale green space regulation is accurately determined by balancing vulnerable areas of green space supply and replenishing green space resources for the ageing population. The findings suggest a Gini coefficient of 0.58 for the supply and demand of green spaces in Shenyang’s central metropolitan region, indicating a relatively low level of equalization in overall green space allocation. Based on location entropy, the classification of supply and demand at the street level yields the following outcomes: balanced areas comprise 21.98%, imbalanced areas account for 26.37%, and highly imbalanced regions represent 51.65%. After eliminating the balanced regions, the distribution of the elderly population is factored in, highlighting the spatial distribution and proportions of communities with distinct regulatory priorities: Level 1 (S1) constitutes 7.4%, Level 2 (S2) accounts for 60.9%, and Level 3 (S3) represents 31.7%. Notably, the communities in the S1 category exhibit spatial distribution characteristics of aggregation within the inner ring and the northern parts of the third ring. This precise identification of areas requiring urgent regulation and the spatial distribution of typical communities can provide reliable suggestions for prioritizing green space planning in an age-friendly city. Full article

Escherichia albertii is an emerging, enteric pathogen of significance. It was first isolated in 2003 from a pediatric diarrheal sample from Bangladesh. In this study, a comprehensive in silico strategy was followed to first list out antibiotic-resistant genes from core, accessory and unique genome fractions of 95 available genomes of E. albertii. Then, 56 drug targets were identified from the core essential genome. Finally, ZipA, an essential cell division protein that stabilizes the FtsZ protofilaments by cross-linking them and serves as a cytoplasmic membrane anchor for the Z ring, was selected for further downstream processing. It was computationally modeled using a threading approach, followed by virtual screening of two phytochemical libraries, Ayurvedic (n = 2103 compounds) and Traditional Chinese Medicine (n = 36,043 compounds). ADMET profiling, followed by PBPK modeling in the central body compartment, in a population of 250 non-diseased, 250 cirrhotic and 250 renally impaired people was attempted. ZINC85624912 from Chinese medicinal library showed the highest bioavailability and plasma retention. This is the first attempt to simulate the fate of natural products in the body through PBPK. Dynamics simulation of 20 ns for the top three compounds from both libraries was also performed to validate the stability of the compounds. The obtained information from the current study could aid wet-lab scientists to work on the scaffold of screened drug-like compounds from natural resources and could be useful in our quest for therapy against antibiotic-resistant E. albertii. Full article

The adsorption of helium on charged hexabenzocoronene (Hbc, C₄₂H₁₈), a planar polycyclic aromatic hydrocarbon (PAH) molecule of D_6h symmetry, was investigated by a combination of high-resolution mass spectrometry and classical and quantum computational methods. The ion abundance of He_nHbc⁺ complexes versus size n features prominent local anomalies at n = 14, 38, 68, 82, and a weak one at 26, indicating that for these “magic” sizes, the helium evaporation energies are relatively large. Surprisingly, the mass spectra of anionic He_nHbc⁻ complexes feature a different set of anomalies, namely at n = 14, 26, 60, and 62, suggesting that the preferred arrangement of the adsorbate atoms depends on the charge of the substrate. The results of our quantum calculations show that the adsorbate layer grows by successive filling of concentric rings that surround the central benzene ring, which is occupied by one helium atom each on either side of the substrate. The helium atoms are fairly localized in filled rings and they approximately preserve the D_6h symmetry of the substrate, but helium atoms in partially filled rings are rather delocalized. The first three rings contain six atoms each; they account for magic numbers at n = 14, 26, and 38. The size of the first ring shrinks as atoms are filled into the second ring, and the position of atoms in the second ring changes from hollow sites to bridge sites as atoms are filled into the third ring. Beyond n = 38, however, the arrangement of helium atoms in the first three rings remains essentially frozen. Presumably, another ring is filled at n = 68 for cations and n = 62 for anions. The calculated structures and energies do not account for the difference between charge states, although they agree with the measurements for the cations and show that the first solvation shell of Hbc^± is complete at n = 68. Beyond that size, the adsorbate layer becomes three-dimensional, and the circular arrangement of helium changes to hexagonal. Full article

Given its remarkable property to easily switch between different oxidative states, iron is essential in countless cellular functions which involve redox reactions. At the same time, uncontrolled interactions between iron and its surrounding milieu may be damaging to cells and tissues. Heme—the iron-chelated form of protoporphyrin IX—is a macrocyclic tetrapyrrole and a coordination complex for diatomic gases, accurately engineered by evolution to exploit the catalytic, oxygen-binding, and oxidoreductive properties of iron while minimizing its damaging effects on tissues. The majority of the body production of heme is ultimately incorporated into hemoglobin within mature erythrocytes; thus, regulation of heme biosynthesis by iron is central in erythropoiesis. Additionally, heme is a cofactor in several metabolic pathways, which can be modulated by iron-dependent signals as well. Impairment in some steps of the pathway of heme biosynthesis is the main pathogenetic mechanism of two groups of diseases collectively known as porphyrias and congenital sideroblastic anemias. In porphyrias, according to the specific enzyme involved, heme precursors accumulate up to the enzyme stop in disease-specific patterns and organs. Therefore, different porphyrias manifest themselves under strikingly different clinical pictures. In congenital sideroblastic anemias, instead, an altered utilization of mitochondrial iron by erythroid precursors leads to mitochondrial iron overload and an accumulation of ring sideroblasts in the bone marrow. In line with the complexity of the processes involved, the role of iron in these conditions is then multifarious. This review aims to summarise the most important lines of evidence concerning the interplay between iron and heme metabolism, as well as the clinical and experimental aspects of the role of iron in inherited conditions of altered heme biosynthesis. Full article

Understanding the water-use strategy of human-planted species used in response to climate change is essential to optimize afforestation programs in dry regions. Since 2000, trees on the central Loess Plateau have experienced a shift from strengthening drought to weakening drought. In this study, we combined tree-ring δ¹³C and δ¹⁸O records from Pinus tabuliformis (syn. tabulaeformis) Carr. (a tree) and Sophora viciifolia Hance (a shrub) on the central Loess Plateau to investigate species-specific responses to rising atmospheric CO₂ (C_a) and drought. We found summer relative humidity controlled the fractionation of tree-ring δ¹⁸O, but the magnitude of the climate influence on δ¹³C differed between the species. The intrinsic water-use efficiency (iWUE) trends of both species suggested a strongly active response to maintain constant intercellular CO₂ concentrations as C_a rose. The tree-ring δ¹³C and δ¹⁸O of both species using first-difference data were significantly and positively correlated, with stronger relationships for the shrub. This indicated the dominant regulation of iWUE by stomatal conductance in both species, but with greater stomatal control for the shrub. Moreover, the higher mean iWUE value of S. viciifolia indicated a more conservative water-use strategy than P. tabuliformis. Based on our commonality analysis, the main driver of the increased iWUE was the joint effect of C_a and vapor-pressure deficit (25.51%) for the tree, while it was the joint effect of C_a and the self-calibrated Palmer drought severity index (39.13%) for the shrub. These results suggest S. viciifolia will be more drought-tolerant than P. tabuliformis and as C_a continually rises, we should focus more on the effects of soil drought than atmospheric drought on the water-use strategy of S. viciifolia. Full article

Electrochemical machining (ECM) is an essential method for machining miniature bearing outer rings on the high-temperature-resistant nickel-based alloy GH4169. However, the influence of electrolyte temperature distribution and bubble rate distribution on electrolyte conductivity in the ECM area could not be fully considered, resulting in the simulation model not being able to accurately predict the machining accuracy of the outer ring of the miniature bearing, making it challenging to model and predict the optimal process parameters. In this paper, a multiphysics field coupled simulation model of electric, flow, and temperature fields during the ECM of the miniature bearing outer ring is established based on the gas–liquid two-phase turbulent flow model. The simulation analyzed the distribution of electrolyte temperature, bubble rate, flow rate, and current density in the machining area, and the profile change of the outer ring of the miniature bearing during the machining process. The analysis of variance and significance of machining voltage, electrolyte concentration, electrolyte inlet flow rate, and interaction on the mean error of the ECM miniature bearing outer rings was derived from the central composite design. The regression equation between the average error and the process parameters was established, and the optimal combination of process parameters for the average error was predicted, i.e., the minimum value of 0.014 mm could be achieved under the conditions of a machining voltage of 16.20 V, an electrolyte concentration of 9.29%, and an electrolyte inlet flow rate of 11.84 m/s. This is important to improve the machining accuracy of the outer ring of the ECM miniature bearing. Full article