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This paper conducted a comprehensive investigation into the role of polymers in cement-based materials. First, the modification mechanism of polymers on cement-based materials based on physical and chemical effects are analyzed. The polymers are adsorbed on the surface of cement particles and cement hydration products through electrostatic attraction or hydrogen bonding, and filled in the pores or interfacial areas, and then transformed into a three-dimensional interpenetrating network structure, so as to densify the matrix materials. Then, the effects of polymers on the cement hydration reaction were introduced. It is mainly attributed to the adsorption behavior between polymer particles, and polymer films with cement causes them to cover the surfaces of cement particles and hydration products, which to some extent restricts the effective diffusion of various ions, such as Ca2+, AlO2−, SiO42−, SO42−, etc., as well as water in the system. And the complexation of functional groups in the polymer with Ca2+ hinders the nucleation and precipitation of calcium-containing hydration products, which in turn delays the hydration reaction process. In terms of strength, as it can be due to the agglomeration of polymer chains, increased porosity arised from generated CO2 gas and entrained air during preparation, the improvement effect of the polymers on cement-based material's compressive strength is not apparent or it shows a decreasing trend. As the role of “microfibers” and “bridge”, many filamentous or network structures composed of flexible polymer membranes dramatically improve the flexural strength and toughness, and also enhance the bonding property of the matrix material. It is expected that the polymers containing designed specific structures according to target property will be applied in cement-based materials, and the universal guidelines and regulations will be provide for expanded application of polymer modified cement-based materials (PMCBMs) in the construction industry.

For hydrocarbon exploitation in tight glutenite, glutenite brittleness plays an important role in fracturing efficiency, but the detailed effect is not entirely clear. In this study, considering rock heterogeneity, RFPA (Rock Failure Process Analysis) was applied to establish the three-dimension computational model. An improved rock brittleness index considering post-peak properties in rock uniaxial compression test was proposed to quantify the glutenite brittleness. Results show that brittle glutenite can generate multiple failure surfaces under the exterior loadings, which can be a mirror to reveal the denser development of natural fractures in the brittle reservoir, while the ductile glutenite is prone to generate a simple shear failure. Hydraulic fractures propagate faster in more brittle glutenite and can generate short branches, which is beneficial to connect the reservoir natural fractures and form complex hydraulic fractures. Brittle glutenite requires a lower treatment pressure than the ductile glutenite, which can provide convenience for ground pumping operation. Hydraulic fractures prefer to propagate in brittle glutenite, rather than the ductile glutenite. The obtained conclusions can provide a reference for the similar practice.

Fractured rock mass with non-equal width filling often appears in the tunel engineering, the non-equal width ratio is the ratio of the filling width at the seepage inlet to the outlet. To study the seepage characteristics of FFRM (filling fracture rock mass) in the surrounding rock of the Gaoligongshan railway tunnel, the samples of FFRM with different non-equal width ratios were prepared indoors. The permeability coefficient formula of the non-equal width ratio FFRM was deduced for the permeability measurement. Then the triaxial seepage apparatus was used to conduct high and low confining pressure test. Results show that the permeability coefficient of FFRM with non-equal width ratios is a function of multi-parameter interaction, such as seepage outflow, inlet width and filling porosity. The permeability and confining pressure at LCP (low confining pressure) and HCP (high confining pressure) is the power and translation exponential function, respectively. While the relationship between the permeability and non-equal width ratio under confining pressure-seepage condition is the quadratic function. After the first cycle, the permeability loss of the samples under HCP is larger than that of the LCP, and the recovery degree is less than that of the LCP. The SSC (stress sensitivity coefficient) decreases with the increase of the confining pressure, the recovery degree is poor after the first cycle unloading. The trend of the subsequent cycle is almost consistent and the recovery degree is good, which is more obvious under the action of the HCP. The conclusions obtained in this study provide a reference for the stability evaluation of the surrounding rock in the underground engineering.

The early immature CD34+ acute myeloid leukemia (AML) cell subpopulation-acute myeloid leukemia progenitor cells (APCs), is often resistant to conventional chemotherapy, making them largely responsible for the relapse of AML. However, to date, the eradication of APCs remains a major challenge. We previously reported a naturally occurring secolignan- Peperomin E (PepE) and its analog 6-methyl (hydroxyethyl) amino-2, 6-dihydropeperomin E (DMAPE) that selectively target and induce oxidative stress-mediated apoptosis in KG-1a CD34+ cells (an APCs-like cell line) in vitro. We therefore further evaluated the efficacy and the mechanism of action of these compounds in this study. We found that PepE and DMAPE have similar potential to eliminate primary APCs, with no substantial toxicities to the normal cells in vitro and in vivo. Mechanistically, these agents selectively inhibit TrxR1, an antioxidant enzyme aberrantly expressed in APCs, by covalently binding to its selenocysteine residue at the C-terminal redox center. TrxR1 inhibition mediated by PepE (DMAPE) leads to the formation of cellular selenium compromised thioredoxin reductase-derived apoptotic protein (SecTRAP), oxidation of Trx, induction of oxidative stress and finally activation of apoptosis of APCs. Our results demonstrate a potential anti-APCs molecular target – TrxR1 and provide valuable insights into the mechanism underlying PepE (DMAPE)-induced cytotoxicity of APCs, and support the further preclinical investigations on PepE (DMAPE)-related therapies for the treatment of relapsed AML. Keywords: Peperomin E, Orally bioavailable analog, Acute myeloid leukemia progenitor cells, Oxidative-mediated apoptosis, Thioredoxin reductase 1