Molecular self-assembly offers a ‘bottom-up’ route to fabrication with subnanometre precision of complex structures from simple components. DNA has proved to be a versatile building block for programmable construction of such objects, including two-dimensional crystals, nanotubes, and three-dimensional wireframe nanopolyhedra. Templated self-assembly of DNA into custom two-dimensional shapes on the megadalton scale has been demonstrated previously with a multiple-kilobase ‘scaffold strand’ that is folded into a flat array of antiparallel helices by interactions with hundreds of oligonucleotide ‘staple strands’. Here we extend this method to building custom three-dimensional shapes formed as pleated layers of helices constrained to a honeycomb lattice. We demonstrate the design and assembly of nanostructures approximating six shapes—monolith, square nut, railed bridge, genie bottle, stacked cross, slotted cross—with precisely controlled dimensions ranging from 10 to 100 nm. We also show hierarchical assembly of structures such as homomultimeric linear tracks and heterotrimeric wireframe icosahedra. Proper assembly requires week-long folding times and calibrated monovalent and divalent cation concentrations. We anticipate that our strategy for self-assembling custom three-dimensional shapes will provide a general route to the manufacture of sophisticated devices bearing features on the nanometre scale.
This study aims to identify how individual-level and neighborhood-level factors are associated with residential satisfaction in urban regeneration areas. We conducted a survey of 281 adult residents recruited on-site at six urban regeneration community facilities (URCFs) that had been in operation for at least one year in Daegu, South Korea, and constructed neighborhood-level built environment factors using GIS. Multilevel regression analysis was applied to simultaneously examine how individual-level (level 1) and neighborhood-level (level 2) factors are associated with residential satisfaction. The results indicated that residents who participated more actively in urban regeneration activities reported higher levels of residential satisfaction, and that age integration was also significantly associated with greater satisfaction. Among neighborhood-level built environment factors, a lower proportion of old housing and higher levels of normalized difference vegetation index (NDVI) and water area were related to higher residential satisfaction. These findings indicate that residential satisfaction in urban regeneration areas can be better understood when individual-level characteristics and neighborhood-level built environmental conditions are considered together, highlighting the importance of a multilevel approach that accounts for both levels simultaneously.
P Selvaraju, Rathinavel Nidhya, K Mohanasundaram
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The research work presented an environmentally sustainable ternary geopolymer composite, which uses fly ash, waste foundry sand, and construction and demolition waste C&D as its base materials. The main goal of the study is to develop construction materials that effectively use energy- saving technologies during all building operations. In this study, six mix designs were developed with desired material combinations after testing different WFS and C&D material ratios while keeping fly ash levels constant to assess material strength and durability. The study also used statistical models to examine dry density, water absorption, compressive strength, impact resistance, and abrasion loss. The optimum mix consisted of 30% C&D waste (M3) on various parameters, such as the highest compressive strength of 38 MPa, the lowest water absorption of 7.2%, and increased impact resistance of 15%. The performance enhancement occurred due to the formation of N-A-S-H and C-A-S-H gels. The development occurred through the combination of silica obtained from waste foundry sand, together with calcium derived from C&D fines. The research demonstrates an effective multi-waste valorisation method that creates an environmentally sustainable production process while promoting circular economy principles through its efficient resource usage and low-carbon material production.
Currently, there are difficulties in dealing with higher construction requirements and standards in subway construction management. Therefore, a multi-objective optimization model was constructed based on building information management technology, and an improved non-dominated sorting genetic algorithm III was introduced to optimize the model solution. And experimental verification was conducted. These experiments confirmed that the average HV of the improved algorithm was 0.67, which was higher than the original algorithm’s 0.65, indicating that it had higher convergence and reliability. The solution results of the non-dominated sorting genetic algorithm II showed that the optimized cost was 185.1899 million yuan. The cost of optimizing the original non-dominated sorting genetic algorithm III was 184.6469 million yuan. The total cost of optimizing the research algorithm was 184.1165 million yuan. In addition, the research algorithm had the shortest construction period, ideal cost, and significantly higher quality and safety levels than the comparison algorithms. And its time consumption was only 20 seconds, significantly lower than the comparison algorithms. And its cost was between 183 million to 187.5 million yuan, with higher stability and relatively concentrated distribution of solutions. Overall, the subway construction optimization model based on building information management and non-dominated sorting genetic algorithm III has high effectiveness and can be effectively applied in practical construction management.
We prove that a Poisson boundary of any regular thick Euclidean building, as well as lattices thereof is the space of chambers at infinity of the building with the harmonic measure class. We then use this result to generalize rigidity results of Guirardel-Horbez-Lécureux on morphisms and cocycles from lattices in buildings to groups with negative curvature properties.
We show that building blocks for open- and closed-string amplitudes on AdS are generated by the Drinfeld and Deligne associator, respectively. Our formalism lifts the known associator recursions for flat-space string amplitudes to the AdS picture. This delivers another proof that the AdS building blocks admit low-energy expansions with (single-valued) multiple zeta values as coefficients and provides all-order relations for the integral expressions.