The microstructures ofAtrina pectinata and freshwater mussel shells are investigated by optical microscopy and scanning electron microscopy. The mechanical properties of these shells are ...characterized by nanoindentation and three-point bending tests. Results show that both shells possess a prismatic microstructure mainly composed of columnar crystals and an organic matrix. The fracture toughness of the prismatic structure of Atrina pectinata and freshwater mussel are approximately 1.15 MPa.m1/2 and 0.87 MPa.m1/2, respectively, while the fracture toughness of natural calcite is approximately 0.2 MPa.m1/2. Calculated results from indentations agree with those obtained from the three-point bending tests. The columnar crystal material shows excellent fracture toughness due to grain refinement. In addition, the organic matrix of the prismatic layer can arrest cracks, and thereby improves the fracture toughness.
Highlights • On-treatment HCV RNA monitoring may be useful in difficult-to-treat patients who receive DAA-based therapies. • Most DAA approval studies used the HPS/CTM assay for HCV RNA testing, ...whereas the CAP/CTM assay is more widely used in clinical practice. • We observed different HCV RNA kinetics with the two assays in our study. • HCV RNA was below the limit of quantification according to both assays at treatment week 8. • On-treatment HCV RNA was not predictive of SVR with either assay.
Cavefish, with sensitive lateral lines, can swim freely and locate preys in invisible and complex cave environments, though their eyes are greatly degenerated. Investigations on the morphology and ...distribution characteristics of their lateral line systems would benefit our understanding of the high-sensitivity mechanism of the fish. In this study, the arrangement and morphology of the lateral lines are described for two species ofSinocyclocheilus： S. macrophthalmus and S. microphthalmus, which live in the karst caves in Guangxi, China. The behavior experiments indicate that the lateral line system of the S. macrophthalmus is more sensitive at a low vibration frequency range from 20 Hz to 70 Hz. The cephalic and trunk lateral line systems both contribute to the efficient object-locating capability. For both of the two species of cavefish, the diameter of the lateral canal nearby the neuromasts is narrower than that nearby the canal pores. This variation can increase the normal pressure to the surface of the cupula, and increase the sensitivity of the canal lateral line system.
Commercial sex is believed to play a role in the steadily increasing heterosexual transmission of HIV in China, but little attention has been paid to female sex workers working in the entertainment ...industry. From October to December 2000, we conducted a cross-sectional survey of 482 women in Baise City, Guangxi Autonomous Region, bordering Yunnan Province. Although no participants had antibodies to HIV infection, 4% of study participants tested positive for markers for syphilis and 21% reported being diagnosed with sexually transmitted diseases in the past year. Women reported low rates of consistent condom use with customers (17%), a spouse or fiance (9%), and casual partners (13%). A substantial proportion experienced condom failure (20% slippage and 13% breakage). Multivariate analyses found that consistent condom use with customers was related to multiple sexual partnerships, higher condom knowledge, and higher condom-use negotiation skills. Multiple sexual partnerships and higher condom-use negotiation skills predicted consistent condom use with casual partners, whereas higher condom-use negotiation skills did so for consistent condom use with a spouse or fiance. Our data suggest the need for condom education, condom skills training, and the distribution of reliable condoms among female sex workers. HIV prevention efforts must target these women as well as their clients and sex partners to prevent the further spread of HIV to the general population in China.
Diatom frustules, considered as novel bio-functional materials, display a diversity of patterns and unique micro- and nanostructures which may be useful in many areas of application. Existing devices ...directly use the original structure of the biosilica frustules, limiting their function and structural scale. Current research into the shapes, materials and structural properties of frustules are considered; a series of frustule processing methods including structure processing, material modification, bonding and assembly techniques are reviewed and discussed. The aim is to improve the function of diatom frustules allowing them to meet the design requirements of different types of micro devices. In addition, the importance of the comprehensive use of diatom processing methods in device research is discussed using biosensors and solar cells as examples, and the potential of bio-manufacturing technology based on diatom frustules is examined.
Numerous natural systems contain surfaces or threads that enable directional water transport. This behaviour is usually ascribed to hierarchical structural features at the microscale and nanoscale, ...with gradients in surface energy and gradients in Laplace pressure thought to be the main driving forces. Here we study the prey-trapping pitcher organs of the carnivorous plant Nepenthes alata. We find that continuous, directional water transport occurs on the surface of the 'peristome'--the rim of the pitcher--because of its multiscale structure, which optimizes and enhances capillary rise in the transport direction, and prevents backflow by pinning in place any water front that is moving in the reverse direction. This results not only in unidirectional flow despite the absence of any surface-energy gradient, but also in a transport speed that is much higher than previously thought. We anticipate that the basic 'design' principles underlying this behaviour could be used to develop artificial fluid-transport systems with practical applications.
Fiber reinforced composite laminates have been increasingly replacing conventional materials in various manufacturing sectors due to their extremely superior mechanical properties. Usually, ...mechanical drilling is an important final manufacturing process for composite laminates, whereas drilling of high-strength composite laminates is very challenging and difficult. As the most undesirable damage and challenging failure mode, drilling-induced delamination for fiber reinforced composite laminates is a hot research area of immerse engineering importance. A review on the path towards delamination-free drilling for composite laminates can significantly help researchers improve currently-available cost-effective drilling process and develop high performance drilling process. This review paper summarizes an up-to-date progress in drilling-induced delamination for composite laminates reported in the literature. It covers delamination formation mechanism, delamination quantification methodologies and measurement technologies, delamination suppression strategies (including tool design optimization, drilling conditions optimization and high performance drilling methods). This general review of drilling-induced delamination for composite laminates can be referenced as not only a summary of the current results from literature survey but also future work possibilities, giving the researchers the opportunity to deepen specific aspects and explore new aspects for reaching delamination-free drilling for composite laminates.
Ultrasonic vibration cutting has been successfully applied in many manufacturing fields due to its superior performances, such as low cutting force, high surface quality and long tool life. However, ...few studies have applied ultrasonic vibration cutting in the field of anti-fatigue manufacturing. In this work, ultrasonic peening cutting is developed to achieve precision-strengthening integrated processing of machined surfaces, which vibration direction is always along with cutting depth direction. Meanwhile, based on analyzing the theoretical motion model of cutting edge, the cutting experiments on Ti-6Al-4V specimens are carried out utilizing ultrasonic peening cutting and conventional cutting respectively. Experimental results show that the average fatigue life of specimens machined by ultrasonic peening cutting with a vibration amplitude of 8 μm is 10.4 times higher than that processed utilizing conventional cutting, and the machined surface roughness of ultrasonic peening cutting increases from Ra0.49μm to Ra0.50μm compared to that machined by conventional cutting.
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