Concretes containing mixed recycled aggregate (RA) have a larger number of coarse aggregate/paste interfacial transition zones (ITZs) than conventional concretes, due to the various component ...materials present in recycled aggregate. This study investigated the properties of various RA/paste ITZs in concrete using nanoindentation and scanning electron microscopy (SEM) and analysed the possible impact of the properties of the ITZs on the macro-mechanical performance of recycled concrete. It was found that the elastic modulus of the ITZ varies with the type of constituent materials present in recycled aggregate, with ITZs associated with organic components (e.g. wood, plastic and asphalt) exhibiting lower minimum elastic modulus values. The impact of ITZ properties on macro-mechanical properties of concrete depends on the relative content of different constituent materials present in the recycled aggregate and the micro-mechanical properties of the ITZs involved.
Pancreatic cancer is a complex disease accounting for fibrotic tumors and an aggressive phenotype. Gemcitabine (GEM) is used as a standard therapy, which develops chemoresistance leading to poor ...patient outcome. We have recently developed a superparamagnetic iron oxide nanoparticle (SPION) formulation of curcumin (SP-CUR), which is a nontoxic, bioactive anti-inflammatory/anti-cancer agent for its enhanced delivery in tumors. In this study, we demonstrate that SP-CUR effectively delivers bioactive curcumin to pancreatic tumors, simultaneously enhances GEM uptake and its efficacy. Mechanistic revelations suggest that SP-CUR targets tumor microenvironment via suppression of sonic hedgehog (SHH) pathway and an oncogenic CXCR4/CXCL12 signaling axis that inhibits bidirectional tumor-stromal cells interaction. Increased GEM uptake was observed due to upregulation of the human nucleoside transporter genes (DCK, hCNT) and blocking ribonucleotide reductase subunits (RRM1/RRM2). Additionally, co-treatment of SP-CUR and GEM targets cancer stem cells by regulating pluripotency maintaining stemness factors (Nanog, Sox2, c-Myc and Oct-4), and restricting tumor sphere formation. In an orthotopic mouse model, an enhanced accumulation of SP-CUR was found in pancreas, which potentiated GEM to reduce tumor growth and metastasis. Analysis of tumor tissues suggest that the treatment inhibits tumor stroma (α-SMA, Desmin and Hyluronic Acid) and induces changes in cell stiffness, as measured via Atomic Force Microscopy. This was accompanied by alteration of key cellular proteins of SHH signaling such as SHH, Gli-1, Gli-2, Sufu, and NFĸB-65 as indicated by Immunoblotting and Immunohistochemistry. These results suggest that SP-CUR has a great potential for future clinical use in the management of pancreatic cancer.
This paper aims to investigate the effect of hydrogen-induced mechanical degradation of low carbon steel at macro-, micro- and nano-levels in the hydrogen-rich acidic environments. From the test ...results of specimens, a relationship in hydrogen concentration and corrosion propagation was observed that led to the significant reductions of bulk elastic modulus after 28 days of exposure to the hydrogen-rich acidic environments. Through microstructural analysis, the deformation of larger grains, cracks, and blisters caused by hydrogen penetration was found as the possible cause for this reduction. Moreover, by performing nanoindentation on the areas of interest of various specimens at planned time periods, the influence of hydrogen on the nano-elastic and nano-hardness properties of grains was determined. The 3D surface profiles of the nano-elastic modulus and nano-hardness of various specimens are presented in this paper.
•The hydrogen embrittlement (HE) behavior of low carbon steel was investigated.•Hydrogen-rich acidic corrosive environments were used, and their effects analyzed.•Hydrogen assisted cracking, blister, and grain boundary deterioration were detected.•Nanoelastic and nanomechanical properties changes due to HE were investigated.•Nanoelastic modulus reduced to 45% in some of the grains due to HE.
Biological materials, such as bones, teeth and mollusc shells, are well known for their excellent strength, modulus and toughness
. Such properties are attributed to the elaborate layered ...microstructure of inorganic reinforcing nanofillers, especially two-dimensional nanosheets or nanoplatelets, within a ductile organic matrix
. Inspired by these biological structures, several assembly strategies-including layer-by-layer
, casting
, vacuum filtration
and use of magnetic fields
-have been used to develop layered nanocomposites. However, how to produce ultrastrong layered nanocomposites in a universal, viable and scalable manner remains an open issue. Here we present a strategy to produce nanocomposites with highly ordered layered structures using shear-flow-induced alignment of two-dimensional nanosheets at an immiscible hydrogel/oil interface. For example, nanocomposites based on nanosheets of graphene oxide and clay exhibit a tensile strength of up to 1,215 ± 80 megapascals and a Young's modulus of 198.8 ± 6.5 gigapascals, which are 9.0 and 2.8 times higher, respectively, than those of natural nacre (mother of pearl). When nanosheets of clay are used, the toughness of the resulting nanocomposite can reach 36.7 ± 3.0 megajoules per cubic metre, which is 20.4 times higher than that of natural nacre; meanwhile, the tensile strength is 1,195 ± 60 megapascals. Quantitative analysis indicates that the well aligned nanosheets form a critical interphase, and this results in the observed mechanical properties. We consider that our strategy, which could be readily extended to align a variety of two-dimensional nanofillers, could be applied to a wide range of structural composites and lead to the development of high-performance composites.
•Ec- fc equation under joint influence of modified fly ash and recycled aggregate.•Recycled fine aggregate quality and volume content are factors on Ed- fc.•R2 variation trends of Ed-pore and εd-pore ...are fairly consistent.
The effects of modified fly ash (MFA) on the replacement rate of cement, the quality and replacement rate of recycled fine aggregates (RFA), the mechanical properties of concrete, such as compressive strength (fc), static elastic modulus (Ec), dynamic elastic modulus (Ed), and durability, i.e., drying shrinkage (ε), were investigated in this study. Based on the data and discussion of the results, different linear correlations were found between Ec and Ed, and the concrete’s age was found to be an important influencing factor. A new equation about Ec and fc of concrete was proposed, as well as the relationship between Ed and fc, and the correlation coefficients were analyzed by the quality and substitution of recycled fine aggregates, and it was confirmed that they were two important influencing factors. Finally, the correlation between Ed and ε and the pore volume in the pore diameter interval of concrete was investigated under the influence of the quality and replacement rate of aggregates and the replacement rate of MFA, and it was found that the variation of Ed and ε on the pore volume correlation coefficient was highly consistent.
Conventionally, engineers have employed rigid materials to fabricate precise, predictable robotic systems, which are easily modelled as rigid members connected at discrete joints. Natural systems, ...however, often match or exceed the performance of robotic systems with deformable bodies. Cephalopods, for example, achieve amazing feats of manipulation and locomotion without a skeleton; even vertebrates such as humans achieve dynamic gaits by storing elastic energy in their compliant bones and soft tissues. Inspired by nature, engineers have begun to explore the design and control of soft-bodied robots composed of compliant materials. This Review discusses recent developments in the emerging field of soft robotics.
A lightweight, flexible, and highly efficient energy management strategy is needed for flexible energy-storage devices to meet a rapidly growing demand. Graphene-based flexible supercapacitors are ...one of the most promising candidates because of their intriguing features. In this report, we describe the use of freestanding, lightweight (0.75 mg/cm2), ultrathin (<200 μm), highly conductive (55 S/cm), and flexible three-dimensional (3D) graphene networks, loaded with MnO2 by electrodeposition, as the electrodes of a flexible supercapacitor. It was found that the 3D graphene networks showed an ideal supporter for active materials and permitted a large MnO2 mass loading of 9.8 mg/cm2 (∼92.9% of the mass of the entire electrode), leading to a high area capacitance of 1.42 F/cm2 at a scan rate of 2 mV/s. With a view to practical applications, we have further optimized the MnO2 content with respect to the entire electrode and achieved a maximum specific capacitance of 130 F/g. In addition, we have also explored the excellent electrochemical performance of a symmetrical supercapacitor (of weight less than 10 mg and thickness ∼0.8 mm) consisting of a sandwich structure of two pieces of 3D graphene/MnO2 composite network separated by a membrane and encapsulated in polyethylene terephthalate (PET) membranes. This research might provide a method for flexible, lightweight, high-performance, low-cost, and environmentally friendly materials used in energy conversion and storage systems for the effective use of renewable energy.
Many biological tissues offer J-shaped stress-strain responses, since their microstructures exhibit a three-dimensional (3D) network construction of curvy filamentary structures that lead to a ...bending-to-stretching transition of the deformation mode under an external tension. The development of artificial 3D soft materials and device systems that can reproduce the nonlinear, anisotropic mechanical properties of biological tissues remains challenging. Here we report a class of soft 3D network materials that can offer defect-insensitive, nonlinear mechanical responses closely matched with those of biological tissues. This material system exploits a lattice configuration with different 3D topologies, where 3D helical microstructures that connect the lattice nodes serve as building blocks of the network. By tailoring geometries of helical microstructures or lattice topologies, a wide range of desired anisotropic J-shaped stress-strain curves can be achieved. Demonstrative applications of the developed conducting 3D network materials with bio-mimetic mechanical properties suggest potential uses in flexible bio-integrated devices.
Cephalopods such as octopuses have a combination of a stretchable skin and color-tuning organs to control both posture and color for visual communication and disguise. We present an ...electroluminescent material that is capable of large uniaxial stretching and surface area changes while actively emitting light. Layers of transparent hydrogel electrodes sandwich a ZnS phosphor-doped dielectric elastomer layer, creating thin rubber sheets that change illuminance and capacitance under deformation. Arrays of individually controllable pixels in thin rubber sheets were fabricated using replica molding and were subjected to stretching, folding, and rolling to demonstrate their use as stretchable displays. These sheets were then integrated into the skin of a soft robot, providing it with dynamic coloration and sensory feedback from external and internal stimuli.
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•A new auxetic honeycomb was designed by hybriding rhombic and star configurations.•A theoretical model was developed to predict the elastic modulus and Poisson's ratio.•The proposed ...honeycomb possesses higher auxetic effect and larger specific modulus than the star honeycomb.•The proposed honeycomb exhibits enhanced plateau stress and specific energy absorption compared with conventional auxetic honeycombs.
Auxetic structures with negative Poisson's ratio exhibit excellent performance in cushioning, shear resistance and energy absorption, but their load-bearing capacity is usually poor. To address this drawback of the conventional Auxetic structure, a star-rhombic honeycomb (SRH) design is proposed in this paper to improve its load-bearing capacity. Analytical models of the elastic modulus and Poisson's ratio of this structure for different loading directions are developed. Quasi-static compression experiments were conducted on SRH specimens fabricated by selective laser melting (SLM) technique. Good agreement was achieved between the simulated and experimental stress response curves and deformation patterns. It was found that the SRH structure possessed better elastic modulus and energy absorption capacity than the SH structure without sacrificing the auxetic properties. The elastic modulus and Poisson's ratio of SRH under the x loading direction are more sensitive to the changes of structural parameters. An optimum energy absorption performance is achieved for an appropriate ratio of the inner rhombic strut thickness to outer reentrant strut thickness (k = 0.5). The specific energy absorption of SRH is improved by 136% and 75% compared to that of the conventional reentrant honeycomb (RH) and star honeycomb (SH), respectively. It has advantages for application scenarios with requirements for both auxetic and load bearing properties.
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