Nanostructural Deformation Analysis of Calcium Silicate Hydrate in Portland Cement Paste by Atomic Pair Distribution Function

The deformation of nanostructure of calcium silicate hydrate (C-S-H) in Portland cement (PC) paste under compression was characterized by the atomic pair distribution function (PDF), measured using synchrotron X-ray diffraction. The PDF of the PC paste exhibited a unique deformation behavior for a short-range order below 2.0 nm, close to the size of the C-S-H globule, while the deformation for a long-range order was similar to that of a calcium hydroxide phase measured by Bragg peak shift. The compressive deformation of the C-S-H nanostructure was comprised of three stages with different interactions between globules. This behavior would originate from the granular nature of C-S-H, which deforms with increasing packing density by slipping the interfaces between globules, rearranging the overall C-S-H nanostructure. This new approach will lead to increasing applications of the PDF technique to understand the deformation mechanism of C-S-H in PC-based materials

Numerical Simulation for the Internal Flow Analysis of the Linear Compressor with Improved Muffler

The numerical simulation is frequently used to estimate experimental results in fluid flow dynamics. In this paper, we focus on increasing the efficiency of linear compressor by applying modified muffler. Furthermore, we analyze a fluid flow in a suction line of linear compressor by using a computational fluid dynamics. We assume an unsteady flow, compressible, and two dimension axis-symmetric condition. In numerical simulation models, all processes of linear compressor, i.e., compression, discharging, expansion and suction, are continuously performed. Numerical simulation results are compared with experimental data to validate an accuracy of simulation. Furthermore, we show that numerical simulation results are well converged according to time. The results present that the mass flow which flows into the cylinder increases when the pressure in the piston is highly maintained during the suction process

Supercapacitor Performance of Nickel-Cobalt Sulfide Nanotubes Decorated Using Ni Co-Layered Double Hydroxide Nanosheets Grown in Situ on Ni Foam

In this study, to fabricate a non-binder electrode, we grew nickel-cobalt sulfide (NCS) nanotubes (NTs) on a Ni foam substrate using a hydrothermal method through a two-step approach, namely in situ growth and an anion-exchange reaction. This was followed by the electrodeposition of double-layered nickel-cobalt hydroxide (NCOH) over a nanotube-coated substrate to fabricate NCOH core-shell nanotubes. The final product is called NCS@NCOH herein. Structural and morphological analyses of the synthesized electrode materials were conducted via SEM and XRD. Different electrodeposition times were selected, including 10, 20, 40, and 80 s. The results indicate that the NCSNTs electrodeposited with NCOH nanosheets for 40 s have the highest specific capacitance (SC), cycling stability (2105 Fg-1 at a current density of 2 Ag-1), and capacitance retention (65.1% after 3,000 cycles), in comparison with those electrodeposited for 10, 20, and 80 s. Furthermore, for practical applications, a device with negative and positive electrodes made of active carbon and NCS@NCOH was fabricated, achieving a high-energy density of 23.73 Whkg-1 at a power density of 400 Wkg-1

Multiscale characterization of chemical-mechanical interactions between polymer fibers and cementitious matrix

Together with a series of mechanical tests, the interactions and potential bonding between polymeric fibers and cementitious materials were studied using scanning transmission X-ray microscopy (STXM) and microtomography (mu CT). Experimental results.showed that these techniques have great potential to characterize the polymer fiber-hydrated cement-paste matrix interface, as well as differentiating the chemistry of the two components of a bi-polymer (hybrid) fiber-the polypropylene core and the ethylene acrylic acid copolymer sheath. Similarly, chemical interactions between the hybrid fiber and the cement hydration products were observed, indicating the chemical bonding between the sheath and the hardened cement paste matrix. Microtomography allowed visualization of the performance of the samples, and the distribution and orientation of the two types of fiber in mortar. Beam flexure tests confirmed improved tensile strength of mixes containing hybrid fibers, and expansion bar tests showed similar reductions in expansion for the polypropylene and hybrid fiber mortar bars

Discovery of Endothelium and Mesenchymal Properties of Primo Vessels in the Mesentery

Recent evidences demonstrated that endothelial-to-mesenchymal transition (EndMT) has a crucial role in cancer and is recognized as a unique source of cancer-associated fibroblasts (CAFs). Primo vascular system (PVS) is a new circulatory system which may play an important role in cancer metastasis and regeneration. In the current study, we applied previously established time-saving method to identify primo vessels and further investigated the immunocytochemical properties of primo vessels. Both primo vessels and primary primo vessel cells in the mesentery expressed endothelial markers and fibroblast markers. Double-labeling experiments demonstrated that endothelial and fibroblast markers are coexpressed in primo vessels. In addition, under the stimulation of TGF-β1 in vitro, primary primo vessel cells differentiated into fibroblasts. Therefore, we found that primo vessels in the mesentery had a transitional structure between endothelium and mesenchymal. This is a new finding of EndMT in normal postnatal animals

Effects of Incorporating High-Volume Fly Ash into Tricalcium Silicate on the Degree of Silicate Polymerization and Aluminum Substitution for Silicon in Calcium Silicate Hydrate

This study assesses the quantitative effects of incorporating high-volume fly ash (HVFA) into tricalcium silicate (C3S) paste on the hydration, degree of silicate polymerization, and Al substitution for Si in calcium silicate hydrate (C–S–H). Thermogravimetric analysis and isothermal conduction calorimetry showed that, although the induction period of C3S hydration was significantly extended, the degree of hydration of C3S after the deceleration period increased due to HVFA incorporation. Synchrotron-sourced soft X-ray spectromicroscopy further showed that most of the C3S in the C3S-HVFA paste was fully hydrated after 28 days of hydration, while that in the pure C3S paste was not. The chemical shifts of the Si K edge peaks in the near-edge X-ray fine structure of C–S–H in the C3S-HVFA paste directly indicate that Al substitutes for Si in C–S–H and that the additional silicate provided by the HVFA induces an enhanced degree of silicate polymerization. This new spectromicroscopic approach, supplemented with 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectroscopy and transmission electron microscopy, turned out to be a powerful characterization tool for studying a local atomic binding structure of C–S–H in C3S-HVFA system and presented results consistent with previous literature

Chloride Adsorption by Calcined Layered Double Hydroxides in Hardened Portland Cement Paste

This study investigated the feasibility of using calcined layered double hydroxides (CLDHs) to prevent chloride-induced deterioration in reinforced concrete. CLDHs not only adsorbed chloride ions in aqueous solution with a memory effect but also had a much higher binding capacity than the original layered double hydroxides (LDHs) in the cement matrix. We investigated this adsorption in hardened cement paste in batch cultures to determine adsorption isotherms. The measured and theoretical binding capacities (153 mg g−1 and 257 mg g−1, respectively) of the CLDHs were comparable to the theoretical capacity of Friedel's salt (2 mol mol−1 or 121 mg g−1), which belongs to the LDH family among cementitious phases. We simulated chloride adsorption by CLDHs through the cement matrix using the Fickian model and compared the simulation result to the X-ray fluorescence (XRF) chlorine map. Based on our results, it is proposed that the adsorption process is governed by the chloride transport through the cement matrix; this process differs from that in an aqueous solution. X-ray diffraction (XRD) analysis showed that the CLDH rebuilds the layered structure in a cementitious environment, thereby demonstrating the feasibility of applying CLDHs to the cement and concrete industries.This publication was based on work supported in part by Award No. KUS-l1-004021 and No. KUS-C1-018-02, made by King Abdullah University of Science and Technology (KAUST). We acknowledge Sasol Company for a sample of Pural MG 63 HT

Changes in objectively measured outdoor time and physical, psychological, and cognitive function among older adults with cognitive impairments

Background: Older adults with cognitive impairment are at higher risk for various health problems. Although previous studies have suggested going outdoors more frequently might be effective to promote health, no longitudinal studies have examined objectively measured outdoor time in this population. This study examined the relationships between changes in objectively measured outdoor time and physical, psychological, and cognitive functions among older adults with cognitive impairments. Methods: This study was a secondary analysis of a randomized controlled trial (n = 145). The baseline and 1-year follow-up data of outdoor time per day measured by the global positioning system, physical functions (6-minute walk test, 5-repetition chair stand test), psychological functions (Geriatric Depression Scale, simplified World Health Organization Five Well-being Index), and cognitive functions (tablet versions of the Trail-making Test, Symbol Digit Substitution Test, Word Memory Test, Story Memory Test) were used. Results: Multiple regression analyses revealed that changes in outdoor time were significantly associated with changes in 6-minute walk (standardized beta = 0.20, p = 0.048) and 5-repetition chair stand tests (standardized beta = -0.19, p = 0.032) after adjusting for baseline data, basic factors, and trial allocation. However, significant relationships between changes in outdoor time and psychological and cognitive functions were not revealed. Conclusions: The results indicate that maintaining or increasing outdoor time would be effective to prevent declines in physical functions but that a quantitative aspect of going outdoors would have limited impact on psychological and cognitive functions among older adults with cognitive impairment