Concrete is a complex material with a multi-scale structure which plays a critical role concerning permeability and durability. In this paper, a two-dimensional pore structure of the cement paste is considered as a media showing an intermittency phenomenon. On this basis, a multifractal (MF) measure method is employed to analyze the pore structure characteristics, using a digital cross section image acquired by scanning electric microscopy (SEM). The results suggests that the pore structure of cement paste displays special mutiple scaling properties. As investigation scale increases, the spatial distribution characteristics display a transition from random type in low scales to scaling properties in high scales with the existing of a critical scale. More specifically, as for the selected image sample with size (256x256) pixels, the acquired multifractal index spectrum displays quasi-bifractal characteristics, showing two different fractal singularities as scales change. Finally, the multifractal property of pore structure is attributed collective nonlinear physical and chemical interactions in the hydration process.
: ABSTRACT In traditional structural design engineers cover length scales from tens of millimetres to hundreds of meters, about 6 orders of magnitude. Behind the engineers' design work we can discover, in essence, a long tradition of multi-scale modelling! In this contribution the implicit multi-scale structure in the traditional engineering design work is demonstrated. Against the background of that analysis, and the successes of the traditional engineering practice, the potential of multi-scale modelling is outlined and the step to develop models dealing with increasingly smaller scales is discussed. The relevance of micro- and nano-scale models is emphasised, particularly in view of the design of new materials and for predictions of long-term performance of materials and structures. The status and potential of currently used microstructrural models will be outlined and their potential use in future nanoscale research will be discussed. Challenges and constraints of small-scale models for engineering purposes will be addressed. ABSTRACT Keywords INTRODUCTION MULTI-SCALE MODELLING: APPROVED CONCEPT IN CIVIL ENGINEERING MODELLING: A SYNTHETISATION ACTIVITY PITFALLS AND CHALLENGES CONCLUDING COMMENTS AND PROSPECTS REFERENCES
Lactoferrin (Lf) is a conserved iron-binding glycoprotein with antimicrobial activity, which is present in secretions that recover mucosal sites regarded as portals of invaded pathogens. Although numerous studies have focused on exogenous Lf, little is known about its expression of endogenous Lf upon bacterial infection. In this study, we investigated the distribution of Lf in mice intestine during Escherichia coli (E. coli) K88 infection. PCR and immunohistology staining showed that mRNA levels of Lf significantly increased in duodenum, ileum and colon, but extremely decreased in jejunum at 8 h and 24 h after infection. Meanwhile, endogenous Lf was mostly located in the lamina propria of intestine villi, while Lf receptor (LfR) was in the crypts. It suggested that endogenous Lf-LfR interaction might not be implicated in the antibacterial process. In addition, it was interesting to find that the infiltration of neutrophils into intestine tissues was changed similarly to Lf expression. It indicated that the variations of Lf expression were rather due to an equilibrium between the recruitment of neutrophils and degranulation of activated neutrophils. Thus, this new knowledge will pave the way to a more effective understanding of the role of Lf in intestinal mucosal immunity.
Although the application of blast furnace slag and fly ash-based alkali-activated concrete (BFS/FA-AAC) has both economic and environmental benefits, it is limited by the lack of a straightforward mix design method. In this paper, an experiment was conducted to investigate the effect of control factors, including the Na2O/binder ratio, the SiO2/Na2O ratio, the BFS/binder ratio, the water/binder ratio, and the water content on the workability (slump and rheology) of BFS/FA-AAC, and the effect of control factors include the Na2O/binder ratio, the SiO2/Na2O ratio, the BFS/binder ratio, the water/binder ratio, and the curing time on the compressive strength of BFS/FA-AAC. As a result, the influence degree and mechanism of each control factor on the performance of BFS/FA-AAC were quantitively explored and the accuracy of an empirical compressive strength formula was validated. Based on that, a practical mix design method of BFS/FA-AAC was eventually established. It is found that the mixture composition and content of paste can significantly influence the workability of BFS/FA-AAC. The compressive strength of BFS/FA-AAC is determined by control factors when the water content is within 160–195 kg/m3. The mechanical predictive method of BFS/FA-AAC is proven of high accuracy. The mixture designed by this methodology exhibits satisfied fresh and hardened performance as well as high environmental benefits.
The progress for making flat multilayer electron emission structure applied in field emission display is described. The Cr-Cu/ Al 2O 3/ZnS /Ag films grown on glass substrate by the way of vacuum sputtering, the fabrication technology on electron emission properties are studied, and the optimum technical parameter is obtained.
