Investigation on Strength and Pore Structure of Supersulfated Cement Paste

The compressive strength and pore microstructure of supersulfated cement (SSC) pastes with different kinds of gypsum, different treatments on phosphogypsum and different fineness, and ordinary Portland cement, slag Portland cement were investigated. The results indicate that phosphogypsum SSC performs better compared to anhydrite and dihydrate gypsum SSC for strength development, especially at late hydration age. For long curing age, burned at 500 °C for phosphogypsum is better than neutralized with 4 % lime in SSC. The smaller the fineness, the higher the cement hydration degree, especially at early age, more hydration products such as ettringite and C-S-H form, and the strength improves to some extent. Compared to ordinary Portland cement and slag Portland cement, phosphogypsum-based SSC has the lowest strength at early age, while the strength growth rate increases over curing time. The paste strength mainly depends on the average pore size but porosity. SSC paste contains more harmless pore, which is beneficial for pore structure and strength.DOI: http://dx.doi.org/10.5755/j01.ms.24.3.18300</p

Properties and Microstructure of Roller Compacted Concrete With High Volume Low Quality Fly Ash

The properties of roller compacted concrete (RCC) with high dosage low quality fly ash are investigated, including strength, elastic modulus, ultimate tensile strain, drying shrinkage, autogenous deformation and durability, meanwhile the microstructure of the same paste containing low quality fly ash and ground low quality fly ash are studied, too. The properties of RCC containing 60% or more ground fly ash meet the design requirement. The microstructure is also tested by using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry-differential thermal analysis (TG-DTA) and Mercury Intrusion Porosimetry (MIP). The results indicate that ground fly ash plays the role of active component besides the physical filling effect at early age, while after 90 days, the surface of the glass beads is erroded and a lot of calcium silicate hydrate and calcium hydroxide staggered as storied dense structure. Low quality fly ash can accelerate the formation of hydration products, resulting in higher degree of cement hydration and denser microstructure, while the hydration heat in total is reduced. At the age of 90 days, fly ash has significant chemical activity and the properties of RCC will be improved at the later stage.DOI: http://dx.doi.org/10.5755/j01.ms.23.3.16318</p

Comparison Study of Hydration Characteristics Between Cements with 50% and 85% Slag

This study aims at comparing the hydration characteristics between two kinds of cements, the Portland slag cement (PSC) containing 50 wt.% ground granulated blast furnace slag (GGBFS), and the supersulfated cement (SSC) containing 85 wt.% GGBFS. The reason caused the different hydration properties with the same type raw materials were analyzed by determining the compressive strength of the pastes, the hydration heat release and the hydration products at different curing ages. The results show that in PSC system, alkali activation was predominating and it mainly generated hydrated calcium silicate (C-S-H gels) and calcium hydroxide (CH). While in SSC system, the hydration mechanism was the combination of sulfate and alkali excitation, it mainly generated C-S-H gels and ettringite. The compressive strength of PSC was higher than that of SSC at every curing age. However, the difference of the compressive strength between PSC and SSC narrowed gradually as curing age went on. The early compressive strength of PSC was high while at late hydration age it increased slowly. The early compressive strength of SSC was low, while the later compressive strength increased quikly. Compared with PSC, the hydration heat evolution rate of SSC was slower and the hydration heat of SSC was relatively less low. Moreover, the second exothermic peak of SSC delayed. DOI: http://dx.doi.org/10.5755/j01.ms.24.4.17746</p

Progressive Thinning of Visual Motion Area in Lower Limb Amputees

Accumulating evidence has indicated that amputation or deafferentation of a limb induces functional or structural reorganization in the visual areas. However, the extent of the visual areas involved after lower limb amputation remains uncertain. In this investigation, we studied 48 adult patients with unilateral lower limb amputation and 48 matched healthy controls using T1-weighted magnetic resonance imaging. Template-based regions of interest analysis was implemented to detect the changes of cortical thickness in the specific visual areas. Compared with normal controls, amputees exhibited significantly lower thickness in the V5/middle temporal (V5/MT+) visual area, as well as a trend of cortical thinning in the V3d. There was no significant difference in the other visual areas between the two groups. In addition, no significant difference of cortical thickness was found between patients with amputation at different levels. Across all amputees, correlation analyses revealed that the cortical thickness of the V5/MT+ was negatively correlated to the time since amputation. In conclusion, our findings indicate that the amputation of unilateral lower limb could induce changes in the motor-related visual cortex, and provide an update on the plasticity of the human brain after limb injury

Analysis of five deep-sequenced trio-genomes of the Peninsular Malaysia Orang Asli and North Borneo populations

BackgroundRecent advances in genomic technologies have facilitated genome-wide investigation of human genetic variations. However, most efforts have focused on the major populations, yet trio genomes of indigenous populations from Southeast Asia have been under-investigated.ResultsWe analyzed the whole-genome deep sequencing data (30x) of five native trios from Peninsular Malaysia and North Borneo, and characterized the genomic variants, including single nucleotide variants (SNVs), small insertions and deletions (indels) and copy number variants (CNVs). We discovered approximately 6.9 million SNVs, 1.2 million indels, and 9000 CNVs in the 15 samples, of which 2.7% SNVs, 2.3% indels and 22% CNVs were novel, implying the insufficient coverage of population diversity in existing databases. We identified a higher proportion of novel variants in the Orang Asli (OA) samples, i.e., the indigenous people from Peninsular Malaysia, than that of the North Bornean (NB) samples, likely due to more complex demographic history and long-time isolation of the OA groups. We used the pedigree information to identify de novo variants and estimated the autosomal mutation rates to be 0.81x10(-8) - 1.33x10(-8), 1.0x10(-9) - 2.9x10(-9), and 0.001 per site per generation for SNVs, indels, and CNVs, respectively. The trio-genomes also allowed for haplotype phasing with high accuracy, which serves as references to the future genomic studies of OA and NB populations. In addition, high-frequency inherited CNVs specific to OA or NB were identified. One example is a 50-kb duplication in DEFA1B detected only in the Negrito trios, implying plausible effects on host defense against the exposure of diverse microbial in tropical rainforest environment of these hunter-gatherers. The CNVs shared between OA and NB groups were much fewer than those specific to each group. Nevertheless, we identified a 142-kb duplication in AMY1A in all the 15 samples, and this gene is associated with the high-starch diet. Moreover, novel insertions shared with archaic hominids were identified in our samples.ConclusionOur study presents a full catalogue of the genome variants of the native Malaysian populations, which is a complement of the genome diversity in Southeast Asians. It implies specific population history of the native inhabitants, and demonstrated the necessity of more genome sequencing efforts on the multi-ethnic native groups of Malaysia and Southeast Asia