C-S-H Seeds Accelerate Early Age Hydration of Carbonate-Activated Slag and the Underlying Mechanism

The slow hardening process of carbonate-activated slag limits its application as a construction material. This paper aims to provide an acceleration method for the early age hydration of carbonate-activated slag by applying calcium silicate hydrate (C-S-H) seeds and unveil the underlying mechanism. The results show that the incorporation of C-S-H seeds significantly accelerates the early age reaction of carbonate-activated slag and shortens the setting time. With 4% of calcium silicate hydrate (C-S-H) seeds, the 1d-compressive strength of carbonate activates slag can achieve 25.4 MPa. The C-S-H seeds acts as the preferred nucleation sites for the strength-giving phase C-A-S-H gel and the carbonate-containing phases (e.g., calcite, gaylussite, hydrotalcite, etc.), and accelerates hydration. The dormant period of samples with C-S-H seeds becomes negligible, confirming that the seeding effect that controls the saturation limits of the pore solution is the major reason for the accelerated hydration.

[Analysis of Microbial Interaction Law of Mud Membrane in IFAS Process for Treating Low Carbon Source Sewage in South China]

To assess the problem of sewage treatment under the condition of low carbon sources, we carried out a study of activated sludge and a biofilm symbiosis system (IFAS). The occurrence characteristics and interaction law of microorganisms in two phases of sludge membrane under low carbon source conditions were discussed, and their niche and influence on treatment efficiency were clarified. Through a pilot-scale experiment in actual water plants, the biofilm characteristics, sludge membrane activity, and succession law of flora were analyzed, and the microbial structure and interaction in sludge membrane in two phases under the control of different activated sludge ages were compared. The results showed that the sludge concentration in the reactor increased with the increase in SRT under variable SRT. Because the microbial concentration in SRT-H was much higher than that in SRT-L, the competition between mud films in SRT-H was more intense than that in SRT-L, and the pollutant removal efficiency in SRT-H was lower than that in SRT-L. Under the condition of low-carbon feed water, the sludge activity in the IFAS process decreased with the increase in SRT. Under the condition of low SRT(5 d), the nitrification, denitrification, phosphorus accumulation, and phosphorus absorption rate of activated sludge increased by 122%, 88%, 34%, and 44%, respectively, compared with that of high SRT (25 d). However, SRT had little effect on biofilm activity, and there was little difference in nitrification activity and denitrification activity between the two SRTs. Microbial sequencing analysis showed that the functional bacteria of the IFAS process were enriched and transferred with the change in SRT between the two phases of mud membrane. In SRT-L, the functional bacteria that were enriched and transferred between the two phases of mud film owing to the "seeding" effect were mainly unclassified_g__Enterobacteriaceae, whereas in SRT-H, Acinetobacter was mainly used. At the same time, by analyzing the distribution of dominant functional bacteria, it was found that there was some competition between denitrifying bacteria and phosphorus-accumulating bacteria in activated sludge. Under the condition of a lack of organic substrate in the influent, the relative abundance of denitrifying bacteria was obviously higher than that of phosphorus-accumulating bacteria, which indicated that denitrifying bacteria could better adapt to low-carbon source conditions. Thus, they could occupy a dominant competition position, which was mainly reflected in the increase in the relative abundance of aerobic denitrifying bacteria. In addition, the SRT change in the mud phase reacted in the membrane phase, making the residence time of biofilm change correspondingly, thus changing the flora structure, screening out different dominant bacteria genera, and further increasing the difference.

Comparison of Bacterial and Fungal Composition and Their Chemical Interaction in Free Tropospheric Air and Snow Over an Entire Winter Season at Mount Sonnblick, Austria

We investigated the interactions of air and snow over one entire winter accumulation period as well as the importance of chemical markers in a pristine free-tropospheric environment to explain variation in a microbiological dataset. To overcome the limitations of short term bioaerosol sampling, we sampled the atmosphere continuously onto quartzfiber air filters using a DIGITEL high volume PM10 sampler. The bacterial and fungal communities, sequenced using Illumina MiSeq, as well as the chemical components of the atmosphere were compared to those of a late season snow profile. Results reveal strong dynamics in the composition of bacterial and fungal communities in air and snow. In fall the two compartments were similar, suggesting a strong interaction between them. The overlap diminished as the season progressed due to an evolution within the snowpack throughout winter and spring. Certain bacterial and fungal genera were only detected in air samples, which implies that a distinct air microbiome might exist. These organisms are likely not incorporated in clouds and thus not precipitated or scavenged in snow. Although snow appears to be seeded by the atmosphere, both air and snow showed differing bacterial and fungal communities and chemical composition. Season and alpha diversity were major drivers for microbial variability in snow and air, and only a few chemical markers were identified as important in explaining microbial diversity. Air microbial community variation was more related to chemical markers than snow microbial composition. For air microbial communities Cl^–, TC/OC, SO₄^2–, Mg²⁺, and Fe/Al, all compounds related to dust or anthropogenic activities, were identified as related to bacterial variability while dust related Ca²⁺ was significant in snow. The only common driver for snow and air was SO₄^2–, a tracer for anthropogenic sources. The occurrence of chemical compounds was coupled with boundary layer injections in the free troposphere (FT). Boundary layer injections also caused the observed variations in community composition and chemistry between the two compartments. Long-term monitoring is required for a more valid insight in post-depositional selection in snow.

Morphological Engineering of Winged Au@MoS2 Heterostructures for Electrocatalytic Hydrogen Evolution

Molybdenum disulfide (MoS₂) has been recognized as a promising cost-effective catalyst for water-splitting hydrogen production. However, the desired performance of MoS₂ is often limited by insufficient edge-terminated active sites, poor electrical conductivity, and inefficient contact to the supporting substrate. To address these limitations, we developed a unique nanoarchitecture (namely, winged Au@MoS₂ heterostructures enabled by our discovery of the "seeding effect" of Au nanoparticles for the chemical vapor deposition synthesis of vertically aligned few-layer MoS₂ wings). The winged Au@MoS₂ heterostructures provide an abundance of edge-terminated active sites and are found to exhibit dramatically improved electrocatalytic activity for the hydrogen evolution reaction. Theoretical simulations conducted for this unique heterostructure reveal that the hydrogen evolution is dominated by the proton adsorption step, which can be significantly promoted by introducing sufficient edge active sites. Our study introduces a new morphological engineering strategy to make the pristine MoS₂ layered structures highly competitive earth-abundant catalysts for efficient hydrogen production.

Site-Specific Positioning and Patterning of MoS2 Monolayers: The Role of Au Seeding

Monolayers of transition metal dichalcogenides (TMDs) are attractive for various modern semiconductor devices. However, the limited control over the location, yield, and size distribution of the products using current synthesis methods has severely limited their large-scale applicability. Herein, we identify the ability to use metal ( e. g., Au) nanoparticles to seed the growth of MoS₂ monolayers and thereby provide a means to achieve programmable and controllable synthesis. In this study, prepatterned Au seeds are used as heterogeneous nucleation sites to induce the formation of desired geometries of MoS₂ monolayers via chemical vapor deposition. Our experimental and theoretical results shed light on the growth mechanism driving the formation of MoS₂ monolayers at these sites, revealing that the seeding effect originates from the favorable formation energy of MoS₂ on the Au surface. A field-effect transistor with a predesigned channel geometry exhibits electronic performance that compares nicely with previously reported MoS₂ monolayer devices. We believe this study contributes fundamental insights into controlled synthesis of TMD monolayers, making integration of these materials into emerging electronic devices more attainable.

Multistep nucleus formation and a separate subunit contribution of the amyloidgenesis of heat-denatured monellin

Monellin (MN) is a sweet-tasting plant protein known to form fibrous aggregates in the heat-denatured state. Here the amyloid-type aggregation process of MN is extensively characterized. The amyloidgenesis was initiated in a highly denatured state of MN. A seeding effect of skipping a lag phase of the amyloid formation kinetics established a nucleation-dependent aggregation mechanism. A finely controlled experimental protocol revealed an additional prenucleus stage preceding the maturation of the nucleus, indicating that the initial lag phase is composed of multiple conformational events. The results obtained for the aggregation properties of the separate A and B subunit chains of MN and a recombinant single-chain MN suggest that the B chain exclusively contributed to the amyloid-type aggregation. These findings suggest a scheme for the amyloidgenesis of MN and their subunits, and provide a unique model of amyloidgenesis that is regulated by the subunit composition of protein.