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Over the past few years, modular buildings have become an important form of environmentally friendly architecture. Prefabricated construction methods have gained a lot of attention because they produce less construction waste and require less labor and water. However, the seismic performance of modular buildings needs to be improved. This paper proposes a prefabricated steel module with a suspended floor, which is based on a multi-tuned mass damped floor system. This paper also derives the form of a motion equation which is unified with the construction process of modular buildings, which can describe the change law of the mass, stiffness, and damping matrix of the structure in the processes of connecting the main structure with the suspended floor slab and of joining different floors. Since the performances of tuned mass damping devices are closely related to the dynamic characteristics of the structure, this paper uses ABAQUS for numerical analysis and mathematical induction (MI) to propose and verify a simplified method for calculating the lateral stiffness of the entire story from a single module’s lateral stiffness. Based on the principle of reducing the stiffness difference in the structure along different directions, a standard scheme of the horizontal extension of the module building is also specified. The results show that the simplified calculation method is reasonable and that the lateral stiffness of the structure increases linearly with the number of modules. Finally, the recommended values for the tuned frequency ratio and tuned damping ratio are given by investigating the dynamic response of the structure under Gaussian white noise excitation. The results show that the recommended tuning frequency ratio and damping ratio ranges in modular buildings are close to those for FIS buildings.

A novel class II 5-enoylpyruvylshikimate-3-phosphate synthase (EPSPS) was identified from Pseudomonas stutzeri A1501 by complementation of an Escherichia coli auxotrophic aroA mutant. The single amino acid substitution of serine (Ser) for asparagine (Asn)-130 of the A1501 EPSPS enhanced resistance to 200 mM glyphosate. The mutated EPSPS had a 2.5-fold increase for IC50 [glyphosate] value, a 2-fold increase for K i [glyphosate] value, but a K m [PEP] value similar to that of wild type. The effect of the single residue mutation on glyphosate resistance was also analyzed using a computer-based three-dimensional model. [ABSTRACT FROM AUTHOR]

Glyphosate, a powerful nonselective herbicide, acts as an inhibitor of the activity of the enzyme 5-enoylpyruvylshikimate-3-phosphate synthase (EPSPS) encoded by the aroA gene involved in aromatic amino acid biosynthesis. An Escherichia coli mutant AKM4188 was constructed by insertion a kanamycin cassette within the aroA coding sequence. The mutant strain is an aromatic amino acids auxotroph and fails to grow on M9 minimal media due to the inactive aroA. A DNA metagenomic library was constructed with samples from a glyphosate-polluted area and was screened by using the mutant AKM4188 as recipient. Three plasmid clones, which restored growth to the aroA mutant in M9 minimal media supplemented with chloramphenicol, kanamycin, and 50 m M glyphosate, were obtained from the DNA metagenomic library. One of them, which conferred glyphosate tolerance up to 150 m M, was further characterized. The cloned fragment encoded a polypeptide, designated RD, sharing high similarity with other Class II EPSPS proteins. A His-tagged RD fusion protein was produced into E. coli to characterize the enzymatic properties of the RD EPSP protein. [ABSTRACT FROM AUTHOR]