Dynamics of microbial communities associated with flavor formation during sour juice fermentation and the milk fan drying process.

Milk fan is an acid-curd cheese with strong national characteristics (a traditional dairy product of the Bai nationality with a shape like a piece of paper) and a long history in Yunnan province, China. In our previous study, we characterized the microbial community diversity of milk fan, but the succession of microorganisms associated with flavor formation in milk fan is still unknown. Therefore, we examined the predominant microorganisms and their correlations with the formation of flavor in the fermentation of sour juice and drying of milk fan by gas chromatography mass spectrometry, high-throughput 16S rDNA sequencing, intergenic spacer sequencing and metatranscriptome analysis. We found that the relative abundances of Lactobacillus and Issatchenkia initially decreased and then increased with time during the fermentation of sour juice. However, the relative abundances of Acetobacter, Leuconostoc, Lactococcus, Geotrichum, and Dipodascus initially increased and then decreased. During the drying step, the relative abundances of Lactobacillus and Issatchenkia continuously increased and became the dominant microorganisms in the milk fan. The metatranscriptomes generated from the milk fan showed that "carbohydrate metabolism," "translation," and "signal transduction" were the main metabolic functions of the microbial communities. Rhodotorula and Yarrowia contained more differentially expressed genes than other genera, which indicated they may be associated with the production of the characteristic flavor. Furthermore, a Pearson correlation analysis showed that Lactococcus, Rhodotorula, Candida, Cutaneotrichosporon, and Yarrowia were significantly positively correlated with more aroma-active compounds, mainly ethyl acetate, 2-heptanone, isovaleraldehyde, butyric acid, nonanal, and hexanal. In conclusion, these findings contribute to a better understanding of the flavor production mechanism during the production of milk fan.

The critical mixed transport process in remediation agent radial injection into contaminated aquifer plumes.

Accurately depicting the subsurface mixing of radially injected remediation agents with contaminated plumes remains paramount yet challenging for understanding and simulating reactive transport. To address this, the present research employed the mixing dynamics of a potassium permanganate plume injected into a pre-existing contaminated plume. Through combining colour deconvolution and thresholding, we effectively isolated local mixing values within the Gaussian annular narrow mixing zone from the noise of mixed double-plume images. Key findings revealed increasing injection rate promotes plume mixing while adding xanthan gum to increase fluid viscosity moderates interface mixing, reducing mixing zone width by 25.3% and 37.4% for 100 mg/L and 400 mg/L xanthan gum, respectively. Grain size is pivotal, with a 30% increase in mixing areas observed in coarse-grained sands over medium-grained sands. Balancing sufficient mixing and preventing contaminated plume growth is essential for effective remediation. Injection rates below 5 mL/min may suppress contaminated plume expansion, albeit at the possible cost of protracted remediation durations. For the attainment of optimal remediation, it's imperative to harmonize robust mixing processes with the mitigation of contaminated plume expansion - a balance that adding xanthan gum during the initial injection phase seems poised to achieve (xanthan gum optimized the average mixing index (AMI)). These findings provide valuable insights into groundwater plume mixing, supporting effective remediation strategies.

Designable Photo-Responsive Micron-Scale Ultrathin Peptoid Nanobelts for Enhanced Performance on Hydrogen Evolution Reaction.

The development of high-reactive single-atom catalysts (SACs) based on long-range-ordered ultrathin organic nanomaterials (UTONMs) (i.e., below 3 nm) provides a significant tactic for the advancement in hydrogen evolution reactions (HER) but remains challenging. Herein, photo-responsive ultrathin peptoid nanobelts (UTPNBs) with a thickness of ≈2.2 nm and micron-scaled length are generated using the self-assembly of azobenzene-containing amphiphilic ternary alternating peptoids. The pendants hydrophobic conjugate stacking mechanism reveals the formation of 1D ultralong UTPNBs, whose thickness is dictated by the length of side groups that are linked to peptoid backbones. The photo-responsive feature is demonstrated by a reversible morphological transformation from UTPNBs to nanospheres (21.5 nm) upon alternative irradiation with UV and visible lights. Furthermore, the electrocatalyst performance of these aggregates co-decorated with nitrogen-rich ligand of terpyridine (TE) and uniformly-distributed atomic platinum (Pt) is evaluated toward HER, with a photo-controllable electrocatalyst activity that highly depended on both the presence of Pt element and structural characteristic of substrates. The Pt-based SACs using TE-modified UTPNBs as support exhibit a favorable electrocatalytic capacity with an overpotential of ≈28 mV at a current density of 10 mA cm-2. This work presents a promising strategy to fabricate stimuli-responsive UTONMs-based catalysts with controllable HER catalytic performance.

Bottom-Up-Etching-Mediated Synthesis of Large-Scale Pure Monolayer Graphene on Cyclic-Polishing-Annealed Cu(111).

Synthesis of large-scale single-crystalline graphene monolayers without multilayers involves the fabrication of proper single-crystalline substrates and the ubiquitous formation of multilayered graphene islands during chemical vapor deposition. Here, a method of cyclic electrochemical polishing combined with thermal annealing, which allows the conversion of commercial polycrystalline Cu foils to single-crystal Cu(111) with an almost 100% yield, is presented. A global "bottom-up-etching" method that is capable of fabricating large-area pure single-crystalline graphene monolayers without multilayers through selectively etching bottom multilayered graphene underneath large area as-grown graphene monolayer on Cu(111) surface is demonstrated. Terahertz time-domain spectroscopy (THz-TDS) measurement of the pure monolayer graphene film shows a high average sheet conductivity of 2.8 mS and mean carrier mobility of 6903 cm2 V-1 s-1 over a large area. Density functional theory (DFT) calculations show that the selective etching is induced by the much easier diffusion of hydrogen atoms than hydrocarbon radicals across the edges of the top graphene layer, and the simulated selective etching processes based on phase field modeling are well consistent with experimental observations. This work provides new ways toward the production of single-crystal Cu(111) and the synthesis of pure monolayer graphene with high electronic quality.

Growth and Grain Boundaries in 2D Materials.

Grain boundaries (GBs) are a kind of lattice imperfection widely existing in two-dimensional materials, playing a critical role in materials' properties and device performance. Related key issues in this area have drawn much attention and are still under intense investigation. These issues include the characterization of GBs at different length scales, the dynamic formation of GBs during the synthesis, the manipulation of the configuration and density of GBs for specific material functionality, and the understanding of structure-property relationships and device applications. This review will provide a general introduction of progress in this field. Several techniques for characterizing GBs, such as direct imaging by high-resolution transmission electron microscopy, visualization techniques of GBs by optical microscopy, plasmon propagation, or second harmonic generation, are presented. To understand the dynamic formation process of GBs during the growth, a general geometric approach and theoretical consideration are reviewed. Moreover, strategies controlling the density of GBs for GB-free materials or materials with tunable GB patterns are summarized, and the effects of GBs on materials' properties are discussed. Finally, challenges and outlook are provided.

A freestanding electrochromic copolymer for multicolor smart window.

Electrochromic devices with low-cost, energy-saving advantages, and controllable color switching have gained widely attention. Yet, electrochromic materials are limited for smart window due to challenges such as difficulty freestanding, monotonous color change, slow switching capability, and low optical contrast. In this work, a freestanding copolymers based on Poly(N-vinylcarbazole) (PVK) and 3, 4-ethoxylenedioxythiophene (EDOT) are designed. The copolymer as-synthesized by the good secondary film-forming of PVK not only contains the freestanding property of PVK, but also possesses the excellent electrical and electrochemical properties of poly(3, 4-ethoxylenedioxythiophene) (PEDOT). The freestanding copolymer was used to create the multicolor: brown, dark brown, purple, and blue. A high optical contrast of up to 39.1% and a color efficiency of up to 107.00 cm 2C-1 prove a significant coloration and bleaching effect, which is satisfactory for the application of electrochromic devices. Further, an electrochromic device based on P(PVK-co-EDOT) as coloring materials is constructed. This work contributes new ideas into the design of electrochromic smart materials.