Search Results (2)

This study investigates the structural behavior of bahareque earth walls, a traditional construction system commonly used in rural areas of northern South America. Bahareque (wattle and daub) walls, consisting of guadua (a bamboo-like material) or wooden frames filled with soil mixes, have demonstrated considerable resilience in seismic zones due to their lightweight and flexible nature. Despite their widespread use in these communities, limited scientific data exist on their seismic performance under in-plane pseudo-static horizontal loading. This research addresses this gap by experimentally evaluating the seismic behavior of five wall models with different combinations of guadua, wood, and earth filling materials. The methodology included four main phases, namely field visits to document traditional construction techniques, material characterization, prototype testing under pseudo-static loads, and an analysis of mechanical behavior. Key material properties, including compressive strength and Young’s modulus, were determined, alongside the mechanical and physical properties of the infill material, which incorporated natural fibers. Pseudo-static tests were conducted on five wall prototypes, featuring various configurations of guadua and wood frameworks, both with and without soil infill. The walls were subjected to horizontal in-plane loads to assess their deformation capacity, energy dissipation, and failure mechanisms. The results indicated that walls with soil mixture infill—specifically the GSHS (guadua frame with horizontal guadua strips and soil mixture infill) and TSHS (wood frame with horizontal guadua strips and soil mixture infill) configurations—demonstrated the best seismic performance, with maximum displacements reaching up to 166 mm and strengths ranging from 6.4 to 8.4 kN. The study concludes that bahareque walls, particularly those incorporating soil mixes and horizontal guadua strips, exhibit high resilience under seismic conditions and provide a sustainable construction alternative for rural regions. The scope of this study is limited by the exclusion of dynamic seismic simulations, which could offer additional insights into the behavior of bahareque walls under real earthquake conditions. The novelty of this research lies in the direct evaluation of the seismic performance of traditional bahareque configurations, specifically comparing walls constructed with guadua and wooden frameworks, while emphasizing the critical role of soil infill and guadua strips in structural performance. Full article

The Crested Ibis (Nipponia nippon) has long fascinated ornithologists with its enigmatic plumage color change. After more than a century of curiosity, the mystery was finally unraveled in the 1970s, unveiling the mechanism behind this remarkable transformation. Unlike other bird species, the Crested Ibis achieves its nuptial plumage coloration through a unique daubing behavior. After a water-bathing, it applies a sticky black substance secreted by a patch of skin in the neck and throat region. However, the chemical components of this black substance have not been studied in detail until now. To address this issue, we conducted a study to detect the components of the black substance and explore the relationship between sex hormone levels and the secretion of the black substance. We used enzyme-linked immunosorbent assay (ELISA) to measure the monthly changes in steroid hormone levels (estradiol E2, testosterone T, and progesterone PROG) levels in feces. We also analyzed the correlation between sex hormone levels and daubing behavior. The results showed that the sex hormone levels are closely related to the secretion and application of the black substance. In addition, we qualitatively analyzed the chemical components of the black substance using gas chromatography–mass spectrometry (GC-MS), uncovering the presence of 117 distinct chemical components. We assume that the black coloration results from the polymerization of selected chemical constituents among these components. These findings provide a groundwork for further exploration into the biological significance of the black substance. Overall, our study detected components in the black substance and studied how sex hormone levels relate to its secretion. Understanding the hormone effects on coloration helps in precise habitat management, like wetland preservation, crucial for Crested Ibis survival. Implementing hormone-boosting measures during breeding seasons enhances reproduction and health, vital for their conservation. Full article