Search Results (306)

This study investigates the influence of the physical and chemical characteristics of three polycarboxylate ether (PCE) superplasticizers—differing in main-chain length, side-chain density, and dispersing-to-stabilizing polymer ratio (75:25, 50:50, and 25:75)—on the dispersion of calcined clays with varying metakaolinite contents (30.04–74.91 wt%) in synthetic cement pore solution (SCPS). Clays were characterized by XRF, XRD, TGA, FTIR, BET, Blaine fineness, and particle size distribution; PCEs were characterized by FTIR, ¹H NMR, GPC, and zeta potential. Dispersion was assessed via mini-slump tests for water demand, PCE dosage to achieve 260 ± 5 mm spread, and slump retention over 120 min, quantified by a normalized spread retention index (SR₁₂₀). Results revealed that clays with a higher metakaolinite content (58.45–74.91 wt%) and Blaine fineness (up to 13.116 m²/g) required two times higher PCE dosages and exhibited greater water demand due to enhanced surface reactivity and Ca²⁺/carboxylate affinity. Slump retention depended on PCE–clay compatibility: at a low metakaolinite content (30.04 wt%), all PCEs yielded SR₁₂₀ ≈ 1; at higher contents, dispersing-rich PCEs (e.g., 75:25 ratio) sustained superior retention (SR₁₂₀ > 1 in intermediate cases), while stabilizing-rich variants showed rapid loss. Zeta potential values remained close to zero due to the high ionic strength of the SCPS, indicating that electrostatic interactions play only a secondary role in the dispersion process, while steric effects govern the performance of the investigated PCEs. Overall, optimal PCE selection requires matching polymer architecture to clay reactivity for effective dispersion and fluidity retention in sustainable calcined clay systems. Full article

The clinker grinding stage in Portland cement production is highly energy-intensive, primarily due to particle agglomeration and intensified interparticle attractive forces that hinder efficient comminution. Grinding aids (GAs) are routinely employed to mitigate these issues, enhancing grinding efficiency and improving cement performance. However, the undesirable side effects associated with conventional GAs on cementitious systems have spurred interest in modification strategies that can concurrently optimize grinding efficiency and final product quality. In this study, widely used commercial GAs, triisopropanolamine (TIPA), diisopropanolamine (DEIPA), and diethylene glycol (DEG), were chemically modified via esterification with organic acids of different carbon chain lengths. Cement specimens incorporating these modified GAs were produced at two dosages (0.05% and 0.1% by mass of clinker + gypsum), resulting in 24 distinct Portland cement formulations alongside a control mix. The influence of modification on grinding efficiency, particle size distribution (PSD), and powder flowability was investigated. Furthermore, scanning electron microscopy (SEM) was utilized to analyze particle morphology and concrete microstructural characteristics with powder flow behavior. The results indicate that organic acid modification not only facilitates achieving target fineness with lower energy consumption but also markedly improves both the PSD profile and the powder’s flow properties. Specifically, hexanoic acid-modified TIPA and DEIPA, along with propanoic acid-modified DEG, delivered the most favorable outcomes across the evaluated parameters. These findings underscore the potential of developing next-generation, modified GAs that simultaneously enhance energy efficiency and powder handling in cement grinding operations. Full article

Despite decades of studies on symmetric impinging-jet atomization, the combined role of controlled pre-impingement asymmetry and viscosity in setting the instability pathways and droplet statistics of laminar microjets remains insufficiently quantified. The effects of pre-impingement jet-length difference and liquid viscosity on the flow morphologies, instability dynamics, and atomization behavior of laminar impinging microjets are investigated experimentally using high-speed imaging. By systematically varying the jet-length asymmetry and viscosity over a range of Weber numbers, the evolution of liquid-sheet motion and breakup is resolved from synchronized front- and side-view observations. Specifically, the scientific objective of this work is to elucidate how pre-impingement jet-length asymmetry and liquid viscosity jointly regulate the dynamical behavior of laminar impinging microjets, with particular emphasis on regime transitions of liquid-sheet morphologies, the coupling between upper-sheet oscillations and rim instabilities revealed by synchronized multi-view imaging and POD-based frequency analysis and the resulting droplet-size statistics. These aspects address physical questions that have not been systematically resolved in classical impinging-jet studies, which predominantly focus on symmetric configurations or performance-oriented atomization. With increasing Weber number, the flow undergoes a sequence of regime transitions, including merged-jet, liquid-chain, wavy-rim, fishbone, closed-rim, open-rim, and arc-shaped atomization states. The presence and extent of the closed-rim regime depend sensitively on both jet-length asymmetry and liquid viscosity. Increasing jet-length difference accelerates transitions between these regimes, whereas increasing liquid viscosity stabilizes the liquid sheet and shifts the onset of unsteady breakup to higher Weber numbers. Proper orthogonal decomposition is applied to time-resolved image sequences to extract dominant oscillatory modes and their characteristic frequencies. Within the fishbone regime, the oscillation frequency of rim deformation either coincides with that of the upper region of the liquid sheet or appears as its subharmonic, indicating period-doubling behavior under specific combinations of Weber number and jet-length asymmetry. These frequency characteristics govern the spatiotemporal organization of ligament formation and detachment along the sheet rim. In the arc-shaped atomization regime, droplet-size distributions follow a log-normal form, and at sufficiently high Weber numbers, the mean droplet diameter shows only a weak dependence on jet-length asymmetry. These findings provide microscale-regime guidance for tunable droplet formation in open microfluidic jetting and related small-scale multiphase flows. The innovation of this study lies in the systematic use of synchronized multi-view imaging combined with POD-based frequency analysis and droplet statistics to directly connect liquid-sheet oscillations, rim instability dynamics, and breakup organization under controlled geometric asymmetry and viscosity variations. This approach enables a unified physical interpretation of regime transitions and instability mechanisms that cannot be resolved from single-view observations or morphology-based classification alone. Full article

The solar-driven conversion of CO₂ into long-chain (C₃₊) products offers a sustainable pathway to mitigate climate change, produce carbon-neutral fuels and value-added chemicals. Over the past few decades, significant advances have been achieved in CO₂ photoreduction; however, most systems still favor C₁ products (CO, CH₄) or C₂ intermediates. However, the synthesis of C₃₊ products poses a formidable challenge due to the complex multi-electron transfer steps required for C–C bond formation. This review provides a concise overview of recent progress in solar-driven photocatalytic and photothermal CO₂ reduction, with a specific focus on the formation of C₃₊ products. The fundamental principles are discussed, including the critical role of C–C coupling mechanisms and the stepwise reaction pathways for C₃₊ products. It highlights how the extended carbon chain length significantly increases the complexity and reduces selectivity, with the suppression of side reactions being a primary research objective. Key catalytic strategies, such as the use of copper-based materials, are examined for their unique ability to facilitate these demanding transformations. Finally, the major challenges are outlined, and a future outlook for this field is provided, with an emphasis on the need for advanced catalyst design and in situ characterization to unlock the potential of solar fuels. Full article

In this study, the effects of molecular structure parameters of polycarboxylate ether (PCE)-based grinding aids (GAs) on grinding efficiency, cement properties, and powder flowability were systematically investigated. Existing literature indicates that only limited attention has been given to a comprehensive evaluation of the combined influence of PCE molecular weight, main chain-to-side chain ratio, and side chain characteristics on the grinding process and powder behavior. Within this framework, seven different PCE-based GAs were synthesized by systematically varying the main chain length, side chain length, and side chain/main chain ratio. The structural characterization of the synthesized additives was carried out using Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). Subsequently, the grinding efficiency, particle size distribution (PSD), and powder flowability of cements produced at two different GA dosages were evaluated in detail. The results demonstrated that increasing the GA dosage generally enhanced grinding efficiency and led to a narrower particle size distribution. An increase in main chain length at a constant side chain length improved grinding performance, whereas PCEs with a medium main chain length exhibited superior powder flowability. In contrast, increasing the side chain length alone had a limited effect on grinding efficiency. Considering all structural parameters collectively, the PCE5 additive—characterized by medium main and side chain lengths and a low side chain/main chain ratio—exhibited the most balanced and overall highest performance. Full article

Proteins are generally characterized by three-dimensional structures that are well suited for their specific function. It is much less accepted that a particular flexibility or plasticity of a protein is essential for performing its function. The latter plasticity encompasses the stochastic motions of small protein sidechains on the picosecond timescale that serve as “lubricating grease”, allowing slower functionally relevant conformational changes. Some remarkable examples of potential correlations between protein dynamics and function were observed for pigment–protein complexes in photosynthesis. For example, electron transfer and protein plasticity are concurrently suppressed in Photosystem II upon decreases in temperature or hydration, thus suggesting a prominent functional role of protein dynamics. An unusual dynamics–function correlation was observed for the major light-harvesting complex II, where the dynamics of charged protein residues affect the pigment absorption frequencies in photosynthetic light-harvesting. Generally, proteins exhibit a wide variety of motions on multiple time and length scales. However, there is an approach to characterize the plasticity of a protein as a single effective force constant that permits a straightforward comparison between different protein systems. Within this review, we determine the latter effective force constant for three photosynthetic proteins in different functional and organizational states. The force constant values determined appear to be rather different for each protein and are consistent with the requirements imposed by the various functions. These findings highlight the individual character of a protein’s flexibility and the role(s) it is playing for the specific function. Full article

Lignin is one of the primary biomass resources in nature; however, its highly stable structure makes it difficult to degrade and utilise. As efficient decomposers of lignocellulosic biomass, termites rely on their gut microbiota for digestion. Consequently, termite guts harbour abundant and specialized lignin-degrading microorganisms. In this study, we isolated a bacterium from the termite gut and identified it as Bacillus cereus BC-8. The laccase activity of B. cereus BC-8 reached the maximum of 87.8 U/L at 72 h, and the lignin degradation rate reached 33.66% within 7 days. Furthermore, we analyzed the structural changes in lignin after treatment with this bacterial strain. Field emission scanning electron microscopy observations revealed that the surface structural integrity of lignin was significantly disrupted after treatment. Fourier transform infrared spectroscopy analysis indicated that B. cereus BC-8 affected the side chains and aromatic skeleton structures of lignin. Thermogravimetric analysis further revealed that B. cereus BC-8 disrupted the primary inter-unit β-O-4 ether bonds of lignin. Whole-genome sequencing of B. cereus BC-8 revealed a genome length of 5,374,773 bp and a GC content of 35.34%. Functional gene annotation revealed that the B. cereus BC-8 genome contains genes encoding various lignin-degrading enzymes (laccase, cytochrome P450, and vanillin oxidase) and their auxiliary factors, along with the phenylalanine and benzoic acid metabolic pathways, which are associated with lignin degradation. In conclusion, B. cereus BC-8 can break down the side chains, aromatic skeletons, and β-O-4 ether bonds of lignin molecules, demonstrating excellent lignin degradation ability. At the molecular level, this study elucidates the key genes and metabolic pathways related to lignin degradation in the genome of B. cereus BC-8. Full article

This study systematically investigates the structure–performance relationship of PMA (PolyMethacrylate) viscosity index improvers in new energy vehicle (NEV) transmission fluids. We developed an integrated analytical framework combining spectroscopic and chromatographic techniques to simultaneously characterize its side chain length distribution, molecular weight polydispersity, and branching architecture. Key findings reveal that the kinematic viscosity of formulated oils positively correlates with PMA molecular weight, low-temperature performance is governed by side-chain length (≥C14 fatty alcohols), shear stability is predominantly determined by molecular weight, and nitrogen-modified PMA enhances oxidation resistance by mitigating kinematic viscosity increase. These insights provide actionable guidance for the molecular design of viscosity index improvers and the formulation optimization of advanced lubricants to meet the stringent demands of electric vehicle transmission systems. Full article

Ultra-soft injectable hydrogels are paramount in biomedical applications such as tissue fillers, drug depots, and tissue regeneration scaffolds. Synthetic approaches relying on linear polymers are confronted by the necessity for significant dilution of polymer solutions to reduce chain entanglements. Bottlebrush polymers offer an alternative approach due to suppressed chain overlap and entanglements, which facilitates lower solution viscosities and increased gel softness. Leveraging the bottlebrush architecture in linear-bottlebrush-linear (LBL) block copolymer systems, where L is a thermosensitive linear poly(N-isopropylacrylamide) block, and B is a hydrophilic polyethylene glycol brush block, injectable hydrogels were designed to mimic tissues as soft as the extracellular matrix at high polymer concentrations. Compared to an analogous system with shorter brush side chains, increasing the side chain length enables a decrease in modulus by up to two orders of magnitude within 1–100 Pa at 20 wt% polymer concentrations, near to the physiological water content of ~70%. This system further exhibits thermal hysteresis, enabling stability with inherent body temperature fluctuations. The observed features are ascribed to kinetically hindered network formation by bulky macromolecules. Full article

Background: Cancer remains a major global health challenge, with current therapies often limited by high toxicity and poor selectivity. Lipopeptides, due to their amphiphilic architecture and synthetic accessibility, have emerged as promising anticancer agents. In this study, the in vitro cytotoxic potential and structure–activity relationships (SARs) of a library of 60 synthetic linear lipopeptides (LLPs), including lipopeptide–peptoid chimeras generated via the Ugi four-component reaction, were evaluated against four cancer cell lines (B16F10, HeLa, HT-29, and PC3). Methods: Cytotoxicity was assessed using MTT and crystal violet (CV) assays, and the natural cyclic lipopeptide surfactin was included as a reference. SAR analysis explored the effects of C-terminal functional groups, lipophilic tail length, peptide core size, and side chain modifications. Mechanistic studies involved cell cycle analysis, apoptosis markers (Annexin V/PI staining, caspase-3 activation), and oxidative stress assessment (ROS/RNS and NO production). Results: Several synthetic LLPs showed potent and selective anticancer activity, with IC₅₀ values approximately 3–15 times lower than that of surfactin and with minimal toxicity toward non-cancerous NIH3T3 fibroblasts. Key structural determinants for activity included the presence of a C-terminal ester group, a lipophilic tail of 14–19 carbon atoms, and a tetrapeptide core. LLPs containing phenyl or azide side chains further enhanced cytotoxicity in a cell line-dependent manner. Mechanistic investigations confirmed that active LLPs induce caspase-dependent apoptosis, cell cycle arrest, and oxidative stress. These findings highlight that the synthetic LLPs demonstrate high in vitro anticancer efficacy with favorable selectivity. Conclusions: Synthetic LLPs exhibit potent and selective anticancer activity in vitro. SAR insights and mechanistic findings support their development as next-generation lipopeptide-based therapeutics. Full article

Polymethoxy butyl ether (BTPOM_n), a novel diesel additive developed for suppressing incomplete combustion emissions, was synthesized via an optimized batch slurry method employing n-butanol and trioxane (TOX) over NKC-9 acid cation-exchange resin (90–110 °C). A comprehensive kinetic model elucidated the reaction mechanism, addressing competitive pathways governing both main product formation and key side reactions—specifically polyoxymethylene hemiformals (HD_n) and polyoxymethylene glycols (MG) generation. As the first detailed kinetic investigation of BTPOM_n synthesis, this work provides a fundamental dataset and a robust predictive model that are crucial for process intensification and reactor design. Hybrid optimization integrating genetic algorithms with nonlinear least-squares regression achieved robust parameter estimation, with model predictions showing excellent agreement with experimental data. Thermal effects significantly influenced reaction rates, enhancing decomposition and propagation processes with increasing temperature. Optimal catalyst loading was identified at 3 and 6 wt.%, balancing reaction acceleration and byproduct suppression. Temperature-dependent equilibrium revealed chain length regulation through growth and depolymerization processes. This mechanistic understanding enables predictive reactor design for cleaner fuel additive synthesis. It provides critical insights for developing emission-control technologies in diesel engine systems. Full article

4,6-Diamino-1,3,5-triazine (DT) derivatives typically exhibit excellent liquid crystal properties, attracting numerous researchers interested in enhancing their performance. In this paper, two DT molecules (DT−10 and DT−12) are employed to elucidate the effects of their backbone length and number of branches in the tail chains on self-assembled nanostructures using scanning tunneling microscopy (STM) at the 1-octanoic acid/highly ordered pyrolytic graphite interface, compared to our previous report (2TDT−n, n = 10,12,16,18). DT−10 features a short backbone and a trialkoxy chain tail, whereas DT−12 possesses a long backbone and bifurcated chain tails. STM results reveal that DT−10 assembles into a cross-shaped nanostructure with DT head groups arranged in a head-to-head configuration stabilized by a pair of N–H···N hydrogen bindings (HBs). In contrast, DT−12 assembles into a two-row linear pattern, where DT head groups exhibit a side-by-side arrangement mediated by a pair of N–H···N HBs. Comparison with our previous findings indicates that although variations in backbone length and tail chain branching can modulate the nanostructural features of DT derivatives, the chain length of DT molecules emerges as a pivotal factor governing their assembly architecture. Full article

Bottle-brush polymers with aggrecan-like side chains represent a class of biomimetic macromolecules that replicate key structural and functional features of natural complexes of aggrecans with hyaluronic acid (HA) which are the major components of articular cartilage. In this study, we employ numerical self-consistent field (SCF) modeling combined with analytical theory to investigate the conformational properties of cylindrical molecular bottle-brushes composed of aggrecan-like double-comb side chains tethered to the main chain (the backbone of the bottle-brush). We demonstrate that the architecture of the brush-forming double-comb chains and, in particular, the distribution of polymer mass between the root and peripheral domains significantly influences the spatial distribution of primary side chain ends, leading to formation of a “dead” zone near the backbone of the bottle-brush and non-uniform density profiles. The axial stretching force imposed by grafted double-combs in the main chain, as well as normal force acting at the junction point between the bottle-brush backbone and the double-comb side chain are shown to depend strongly on the side-chain architecture. Furthermore, we analyze the induced bending rigidity and persistence length of the bottle-brush, revealing that while the overall scaling behavior follows established power laws, the internal structure can be finely tuned without altering the backbone stiffness. These theoretical findings provide valuable insights into relations between architecture and properties of bottle-brush-like supra-biomolecular structures, such as aggrecan-hyaluronan complexes. Full article

This study reports the synthesis and characterization of well-defined ionic graft conjugates acting as drug delivery systems, based on monomeric ionic units derived from choline methacrylate (TMAMA) biofunctionalized with the anions of ampicillin (AMP) or cloxacillin (CLX). Using the “grafting from” technique with multifunctional macroinitiators, the density of side chains was precisely defined, and the length of side chains was well-controlled during polymerization. The resulting ionic conjugates featured the regulated content of ionic fractions with drug anions reaching up to 55% and drug content up to 48–70% for AMP, 27–65% for CLX, and 47–79% for (CLX + AMP). The drug release behavior was evaluated under physiological conditions using a dialysis method. The ionic conjugates demonstrated release efficiencies of 70–93% for CLX (5–16 µg/mL), 69–98% for AMP (12–13 µg/mL) in single systems, and 61–73% for CLX + AMP (10–15 µg/mL) in dual systems. Additionally, polymer surface properties were evaluated via water contact angle measurements (WCA = 30–54°). In an aqueous solution, the polymer self-assemblies appeared to be nanosized particles (90–360 nm). The results demonstrate that the synthesized TMAMA-based graft copolymers act as effective ionic conjugates and dual drug systems, offering a promising platform for controlled and multi-drug delivery applications. Full article

Motivated by the strategy developed by Hicks and Dresselhaus in a quantum wire corresponding to a single-chain model with $k^2$-dispersion, we study a one-dimensional double-chain model with two carriers of electrons and holes, characterized by $k^4$-dispersion. To understand the role of the enhancement of the density of state derived from $k^4$-dispersion, we calculate an optimized dimensionless thermoelectric figure of merit ($ZT$) depending on the side length of the cross section, a, in the same way as discussed by Hicks and Dresselhaus. We find that $ZT$ enhances as a decreases similarly to the results obtained in the single-chain model, while the enhancement of $ZT$ is smaller than that of single-chain model. We discuss the reason in connection with the difference of electronic state between the single- and double-chain models. Full article