Experimental Study on the Fracture Toughness of Bamboo Scrimber.

In the past decade, bamboo scrimber has developed rapidly in the field of building materials due to its excellent mechanical properties, such as high toughness and high tensile strength. However, when the applied stress exceeds the ultimate strength limit of bamboo scrimber, cracks occur, which affects the performance of bamboo scrimber in structural applications. Due to the propensity of cracks to propagate, it reduces the load-bearing capacity of the bamboo scrimber material. Therefore, research on the fracture toughness of bamboo scrimber contributes to determining the material's load-bearing capacity and failure mechanisms, enabling its widespread application in engineering failure analysis. The fracture toughness of bamboo scrimber was studied via the single-edge notched beam (SENB) experiment and compact compression (CC) method. Nine groups of longitudinal and transverse samples were selected for experimental investigation. The fracture toughness of longitudinal bamboo scrimber under tensile and compressive loadings was 3.59 MPa·m1/2 and 2.39 MPa·m1/2, respectively. In addition, the fracture toughness of transverse bamboo scrimber under tensile and compressive conditions was 0.38 MPa·m1/2 and 1.79 MPa·m1/2, respectively. The results show that, for this material, there was a significant distinction between longitudinal and transverse. Subsequently, three-point bending tests and simulations were studied. The results show that the failure mode and the force-displacement curve of the numerical simulation were highly consistent compared with the experimental results. It could verify the correctness of the test parameters. Finally, the flexural strength of bamboo scrimber was calculated to be as high as 143.16 MPa. This paper provides data accumulation for the numerical simulation of bamboo scrimber, which can further promote the development of bamboo scrimber parameters in all aspects of the application.

Experimental investigation on mechanical properties of aged bamboo fiber-reinforced composites under quasi-static loading.

Bamboo fiber-reinforced composites (BFRC) have gradually attracted the interest of researchers due to their excellent mechanical properties. However, the age factor can affect these composites' mechanical properties and weaken them. This study aims to explore the mechanical properties of BFRC subjected different aging tests. First, the BFRC is prepared from raw bamboo through a series of technological processes. Second, the BFRC sheets are processed into tensile and compressive samples with different directions. Third, the samples are treated with a cold-hot test and a UV dry-wet test, respectively. Finally, quasi-static experiments are carried out to study the mechanical properties of aged BFRC. The results reveal that the BFRC has significant anisotropy. The tensile strength of BFRC parallel with the axis of the reinforcing fiber is as high as 148.53 MPa. It is 26.47 times greater than the tensile strength of BFRC perpendicular to the axis of the reinforcing fiber. The mechanical responses and SEM images show that the UV dry-wet test significantly affects on the BFRC compared to the cold-hot test. It dramatically reduces the mechanical properties of the BFRC. The SEM images further indicate that cracks occur on the surface of BFRC samples under the UV dry-wet test. In addition, two aging tests have an interactive effect on BFRC, which can reduce the sensitivity of BFRC to a UV dry-wet environment. These results are expected to deepen the understanding of the mechanical properties of BFRC and provide guidance for its applicable conditions.

Plasticity in ventral pallidal cholinergic neuron-derived circuits contributes to comorbid chronic pain-like and depression-like behaviour in male mice.

Nucleus- and cell-specific interrogation of individual basal forebrain (BF) cholinergic circuits is crucial for refining targets to treat comorbid chronic pain-like and depression-like behaviour. As the ventral pallidum (VP) in the BF regulates pain perception and emotions, we aim to address the role of VP-derived cholinergic circuits in hyperalgesia and depression-like behaviour in chronic pain mouse model. In male mice, VP cholinergic neurons innervate local non-cholinergic neurons and modulate downstream basolateral amygdala (BLA) neurons through nicotinic acetylcholine receptors. These cholinergic circuits are mobilized by pain-like stimuli and become hyperactive during persistent pain. Acute stimulation of VP cholinergic neurons and the VP-BLA cholinergic projection reduces pain threshold in naïve mice whereas inhibition of the circuits elevated pain threshold in pain-like states. Multi-day repetitive modulation of the VP-BLA cholinergic pathway regulates depression-like behaviour in persistent pain. Therefore, VP-derived cholinergic circuits are implicated in comorbid hyperalgesia and depression-like behaviour in chronic pain mouse model.

Crash severity analysis of nighttime and daytime highway work zone crashes.

INTRODUCTION: Egypt's National Road Project is a large infrastructure project which presently aims to upgrade 2500 kilometers of road networks as well as construct 4000 kilometers of new roads to meet today's need. This leads to an increase in the number of work zones on highways and therefore a rise in hazardous traffic conditions. This is why highways agencies are shifting towards night construction in order to reduce the adverse traffic impacts on the public. Although many studies have investigated work zone crashes, only a few studies provide comparative analysis of the difference between nighttime and daytime work zone crashes. METHODS: Data from Egyptian long-term highway work zone projects between 2010 and 2016 are studied with respect to the difference in injury severity between nighttime and daytime crashes by using separate mixed logit models. RESULTS: The results indicate that significant differences exist between factors contributing to injury severity. Four variables are found significant only in the nighttime model and four other variables significant in the daytime model. The results show that older and male drivers, the number of lane closures, sidewise crashes, and rainy weather have opposite effects on injury severity in nighttime and daytime crashes. The findings presented in this paper could serve as an aid for transportation agencies in development of efficient measures to improve safety in work zones.