Search Results (1,330)

We report the development of a high-power, cost-effective, and rapidly tunable laser system optimized for rubidium optical pumping in spin-exchange optical pumping (SEOP) applications. The system combines a spectrally narrowed diode laser bar with a low-cost yet high-stability thermal-management architecture based on consumer-grade CPU liquid-cooling components. Wavelength narrowing and fast tuning are achieved by linearly translating a chirped volume Bragg grating (CVBG), providing mode-hop-free, continuous wavelength control without relying on slow thermal tuning mechanisms. Long-term wavelength stability is ensured through a terminal proportional–integral–derivative (PID) feedback loop that locks the laser directly to the rubidium absorption spectrum in the pumping cell, rather than to an internal reference. Operating near 795 nm, the laser delivers up to 40 W of optical power with a measured linewidth of approximately 0.15 nm. The system supports rapid wavelength agility over a continuous tuning range of $794.73\pm 0.24$ nm and exhibits stable spectral performance during extended operation. Owing to its compact design, fast response, and substantially lower cost than conventional volume-grating-based systems, this laser architecture provides a practical and scalable solution for SEOP and other precision atomic and spectroscopic applications that require high power, a narrow linewidth, and robust wavelength stability. Full article

The current state and prospects of microreactor synthesis of functional materials in single- and two-phase flows with a liquid continuous phase are analyzed. Microreactors allow fine control over the size, composition, structure, and properties of synthesized particles in co-precipitation processes. The results obtained by various teams provide grounds to expect fairly extensive capabilities for controlling the processes of nucleation and particle growth in microreactors—by controlling the pH, reagent concentrations, micromixing quality, and residence time in each of the reactor zones—in the nucleation growth zones. The advantages of microreactor synthesis have been demonstrated with a high quality of micromixing in a volume of 0.2–0.5 mL, which ensures the production of nanoparticles without impurities, a stoichiometric ratio of atoms in the product, and limitation of agglomerate growth due to a short residence time (in the order of several milliseconds). The transition to an industrial scale is very easy due to the fairly high productivity of a single microreactor (up to 10 m³/day for suspension, up to 200–300 kg/day for solid phase). Intensive mixing in microreactors with a diameter of 2–4 mm or less, due to Taylor vortices, contributed to the use of two-phase microreactors for the synthesis of both organic and inorganic substances. Full article

The anaerobic digestion process generally generates volatile fatty acids (VFAs) depending upon the metabolic pathway. VFAs are short chain fatty acids containing from one up to eight interlinked carbon atoms. Separation, identification, and quantification of VFAs can enhance metabolic process especially biogas production during anaerobic digestion. Therefore, the continuous monitoring of VFAs is mandatory and is typically performed by liquid chromatography combined with mass spectrometry (LC–MS) and gas chromatography equipped with flame ionization detector (GC–FID) that require sample derivatization and larger sample size of 10–30 mL. Therefore, the current study develops a simple and readily applicable protocol to determine and quantify VFAs (C1–C7) in liquid digestate samples by gas chromatography combined with mass spectrometry (GC–MS) with a reduced sample size of only 0.5 mL. The protocol utilized mix VFAs standard solution for calibration and solvent extraction technique to extract and dissolve VFAs from digestate samples to a volatile solvent dimethyl carbonate (DMC). The results indicate the effective and well separated peaks of all analyte acids from C1 to C7 with regression coefficients r² ≥ 0.98 (C1–C4) and ≥ 0.93 (C5–C7) during calibration. The digestate samples analyzed showed abundance of acetic acid from 4.6 to 11 mM concentration in all four samples followed by propanoic acid (C3) to hexanoic acid (C6) in a range from 0.3 to 4.5 mM concentration. The method is suitable for quantifying all VFAs from C1 to C7 analyte acids as well as the isomers of C4 to C6 analyte acids. Moreover, the method is applicable to a variety of liquid samples from water treatment to energy valorization. Full article

Due to its antioxidant and immunomodulatory properties, using passion fruit seed oil (PFSO) is a promising strategy to mitigate the effects of heat stress in laying hens, potentially optimizing the absorption of essential minerals such as selenium (Se) and zinc (Zn). Therefore, this study investigated the profile of selenium- and zinc-binding proteins (Se/Zn-BPs) in the hepatic proteome of Lohmann White laying hens (26 weeks old, n = 96) subjected to heat stress and whose diet was supplemented with 0.9% PFSO, using a metalloproteomic approach that combined two-dimensional electrophoresis (2D PAGE), graphite furnace atomic absorption spectrometry (GFAAS), and liquid chromatography–tandem mass spectrometry (LC-MS/MS). The experimental design was a 2 × 2 factorial (temperature: thermoneutral/stress × diet: control/PFSO) design. After 84 days, liver samples were collected and subjected to metalloproteomic analyses. GFAAS analysis showed higher concentrations of Zn and Se in the protein pellets and in 11 specific protein spots of the supplemented groups (thermoneutral/PFSO and stress/PFSO). LC-MS/MS analysis identified 56 Se/Zn-BPs, with a predominance of heat shock chaperones (HSPs) and proteins involved in energy metabolism. In conclusion, PFSO supplementation modulates Se and Zn absorption, promoting a mineral balance that optimizes immune and antioxidant defense processes. This mechanism can lead to a positive impact on the health and productive performance of laying hens under heat stress. 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

This paper presents a focused review of a closed-loop system for sustainable hydrogen production utilizing the reaction between metallic aluminum powders and water, coupled with renewable energy-driven recycling of aluminum hydroxide (or alumina) byproducts back to metallic aluminum powders. A green energy closed-loop system based on aluminum could be achieved if the converting process is accomplished by a green Hall–Héroult process, where a cermet inert anode was used. Meanwhile, the byproduct alumina is converted back to the liquid form of aluminum at high temperature (up to 960 °C), producing pure oxygen. A high-pressure atomization process is then used to break the aluminum droplets into powder using argon gas. The technical feasibility, thermodynamic efficiency, economic viability, environmental sustainability, and comparison of this green aluminum cycle with existing hydrogen production and energy storage technologies are discussed. The aluminum–water reaction offers exceptional energy density (29.7 kJ/g of Al), ambient temperature operation, and zero direct carbon emissions. However, commercial implementation faces substantial challenges including overall round-trip energy efficiency (estimated 34.5–46.6%), technological maturity of the recycling process, passivation layer management, and economic competitiveness with conventional water electrolysis. Despite these challenges, the system demonstrates advantages for seasonal energy storage, off-grid applications, and integration with intermittent renewable energy sources. This analysis provides a framework for researchers, engineers, and policymakers to assess the potential role of aluminum-based energy cycles in the global energy transition toward carbon neutrality. Full article

The dispersion state of molecular catalysts critically determines sulfur utilization efficiency and redox kinetics in lithium–sulfur cells. Cobalt phthalocyanine (CoPc) exhibits intrinsic catalytic activity in sulfur redox reactions, owing to its planar π-conjugated framework and highly active Co-N₄ centers. However, its poor solubility in solvents confines active sites to particle surfaces, thereby restricting catalytic utilization. The high flexibility of phthalocyanines allows for the introduction of substituents to modulate solubility. This study aims to utilize the differing solubility of sulfonated cobalt phthalocyanine (CoPcS) in various solvents to achieve distinct loading morphologies on carbon host, investigating the structure–activity relationship induced by catalyst dispersion. In the molecular adsorption configuration, the Co-N₄ active sites exhibit enhanced accessibility to Li₂S₄, where the sulfur atoms engage in stronger electron-transfer interactions with the Co centers. This strengthened orbital coupling weakens the bridging S-S bond and facilitates the liquid–solid conversion. Compared to particle-loaded cathodes, molecularly adsorbed cathodes exhibit a charge transfer impedance approximately 84.6% lower and a high reversible capacity of nearly 800 mAh g⁻¹ at a 3C rate. Particularly at a 0.5C rate, they achieve a high initial specific capacity of nearly 1300 mAh g⁻¹ and maintain over 80% capacity retention after 200 cycles. This study demonstrates that molecular-level dispersion, with effective exposure of active sites, is essential for activating the catalytic potential of molecular catalysts and offers a general molecular-engineering strategy for high-performance lithium–sulfur batteries. Full article

ZnSe nanoparticles were synthesized via the sustainable laser fragmentation in liquids (LFL) technique using a Nd:YAG laser at 1064 nm. The pulse energy was varied to study its effect on the particle size and vibrational properties. UV–Vis absorption spectra show a blue shift in the absorption edge with a decreasing pulse energy. The sample processed at the lowest pulse energy has the smallest nanoparticles (10.3 nm average), reaches an optical band gap of 2.83 eV, and exhibits a high-energy shoulder attributed to spin–orbit-related transitions. Raman spectra reveal a strong enhancement of the surface phonon mode (231–234 cm⁻¹), where its intensity surpasses that of the longitudinal optical mode, demonstrating the dominant role of surface atoms in the vibrational response. TEM confirms a wide size distribution, i.e., centered at 10.3 ± 6.4 nm, which can account for the simultaneous observation of bulk-like and quantum-confined optical and Raman features. These results show that the pulse energy effectively tunes the nanoparticle size and phonon behavior, positioning LFL as a clean and versatile method for producing ZnSe nanostructures with relevant properties for optoelectronic applications. Full article

This study investigated the impact of pH adjustment and carrier type on the physicochemical properties, antioxidant activity, thermal stability, hygroscopicity, and particle size distribution of spray-dried model solutions and carrot juice formulations. Model systems were created at varying pH levels (3, 4, 6, 8, and 10) using water alone or with carriers such as octenyl succinic anhydride (OSA)-modified starch (O), trehalose (T), or a combination (OT in a 1:1 ratio at 9–10%). These systems were compared to carrot juice and formulations of carrot juice that included the same carriers. Spray drying was performed at 160 °C using constant feed flow and atomization conditions. In the liquid samples, we measured pH, dry matter, density, conductivity, and color parameters, while the bioactive compounds were analyzed in carrot juice systems. For the powders, we evaluated the dry matter content, color, particle size distribution, morphology, thermal stability, hygroscopicity, and antioxidant activity. Results showed that in model systems, dry matter, density, and conductivity were more affected by the carrier chemistry than pH. Formulations with OSA had lower pH and higher conductivity due to ionizable groups, while trehalose acted neutrally. OSA-trehalose mixtures yielded the highest solids content and stable properties across pH levels, with particle size (D₅₀ range of 18–21 µm) and morphology of the model powders remaining largely unaffected by pH. In carrot juice formulations, however, particle properties were pH-dependent. Acidic conditions (pH 3–4) led to agglomeration and broader size distributions (indicated by increased span values), while neutral to alkaline conditions produced smaller, more uniform particles with improved thermal stability. Neutral to alkaline conditions favored the formation of smaller, more homogeneous particles and improved thermal resistance. The carotenoid content in carrot juice powders increased from approximately 21–23 mg/100 g dry matter (d.m.) under acidic conditions to about 27–30 mg/100 g d.m. at pH 8–10, which was accompanied by higher ABTS antioxidant activity (around 6–9 mg Trolox equivalents (TE)/g d.m.). In contrast, the polyphenol content was highest at low pH levels (approximately 350–420 mg chlorogenic acid (CA)/100 g d.m.), corresponding to elevated DPPH scavenging activity and reducing power, both of which decreased under alkaline conditions. These findings indicate that pH levels and carrier choice significantly affect spray-dried powders. This highlights the importance of validating model system observations in complex food matrices. By adjusting pH and selecting suitable carriers, we can create powders with improved structures, stability, and antioxidant functionality, particularly in foods like carrot juice. Full article

Bent-shaped liquid crystal (LC) dimers, trimers, and oligomers are intriguing because of their unique liquid crystallinities, which have gained further impetus after the identification of the twist-bend nematic (N_TB) phase in these molecules. LC trimers exhibiting the N_TB phase still remain relatively rare compared to the predominant LC dimers. We report the first homologs of selenium-linked LC trimers, 4,4′-bis[ω-(4-cyanobiphenyl-4′-ylseleno)alkoxy]biphenyls (CBSenOBOnSeCB) with carbon numbers in the alkyl-chain spacers, n = 7 or 9). Polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction (XRD) measurements were performed to investigate the phase transition behavior and mesophase structures of the trimers. Both CBSenOBOnSeCB trimers exhibited nematic (N) and N_TB phases. The XRD measurements revealed the presence of smectic A-like cybotactic clusters with a triply intercalated structure in the N and N_TB phases. The LC phase transition temperatures of CBSenOBOnSeCB were lower than those of the already-known ether-linked CBOnOBOnOCB and thioether-linked CBSnOBOnSCB counterparts. This trend is ascribed to the enhanced molecular bending and molecular flexibility of CBSenOBOnSeCB, which are caused by the smaller bond angle and greater bond flexibility of C–Se–C compared to C–O–C and C–S–C. This study offers a new molecular design for multiply linked LC oligomers with heavier chalcogen atoms. Full article

To mitigate the attenuation of color-change sensitivity in cholesteric liquid crystals (CLCs) post-microencapsulation, this study developed MXene-reinforced thermochromic textiles. Monolayer/few-layer MXene nanosheets were fabricated via an etching-intercalation-dispersion approach, while cholesteric liquid crystal microcapsules (CLCMs) were synthesized through a solvent evaporation method. Cotton fabrics were pretreated with polydopamine (PDA), followed by the fabrication of poly(diallyldimethylammonium chloride) (PDAC)/MXene composite coatings via layer-by-layer (LbL) self-assembly and subsequent hydrophobic modification. Systematic characterizations (scanning electron microscopy, SEM; atomic force microscopy, AFM) and performance evaluations revealed that MXene nanosheets have an average thickness of 1.54 nm, while CLCMs display a uniform spherical morphology. The resultant textiles exhibit a reversible red-green-blue color transition over the temperature range of 26.5–29.5 °C, with sensitivity comparable to pristine CLCs and excellent hydrophobicity. This work overcomes the long-standing bottleneck of inadequate color-change sensitivity in conventional liquid crystal microcapsule textiles, offering a novel strategy for the advancement of smart wearable color-changing materials. Full article

To reveal the physical evolution of methanol spray under different environmental conditions and injection strategies, this study focuses on the atomization and evaporation behavior of low-pressure methanol spray. The coupled effects of temperature, pressure, and injection parameters are systematically investigated based on constant-volume combustion chamber experiments and three-dimensional CFD simulations. The formation, evolution, and interaction mechanisms of the liquid column core and cooling core are revealed. The results indicate that temperature is the dominant factor influencing methanol spray atomization. When the temperature increases from 255 K to 333 K, the spray penetration distance increases by approximately 70%, accompanied by a pronounced shortening of the liquid-core length and enhanced evaporation and air entrainment. Under low-temperature conditions, a stable liquid-core structure and a strong cooling core are formed, characterized by a high-density, long-axis morphology and an extensive low-temperature region, which suppress fuel–air mixing and ignition. Increasing the ambient pressure improves spray–air mixing but reduces penetration; at 255 K, increasing the ambient pressure from 0.05 MPa to 0.2 MPa increases the spray cone angle by approximately 10% while reducing the penetration distance by about 50%. Furthermore, optimizing the injection pressure or shortening the injection pulse width effectively enhances atomization performance: increasing the injection pressure from 0.4 MPa to 0.6 MPa and reducing the pulse width from 5 ms to 2 ms increases the penetration distance by approximately 30% and reduces the mean droplet diameter by about 20%. Full article

Subsurface deposition determines whether soils, aquifers, or ocean sediment represent a sink or temporary reservoir for microplastics. Deposition is generally studied by applying the Smoluchowski–Levich equation to determine a particle’s sticking efficiency, which relates the number of particles filtered by sediment to the probability of attachment occurring from an interaction between particles and sediment. Sticking efficiency is typically measured using column experiments or estimated from theory using the Interaction Force Boundary Layer (IFBL) model. However, there is generally a large discrepancy (orders of magnitude) between the values predicted from IFBL theory and the experimental column measurements. One way to bridge this gap is to directly measure a microparticle’s interaction forces using Atomic Force Microscopy (AFM). Herein, an AFM method is presented to measure sticking efficiency for a model polystyrene microparticle (2 μm) on a model geomaterial surface (glass or quartz) in environmentally relevant, synthetic freshwaters of varying ionic strength (de-ionized water, soft water, hard water). These data, collected over nanometer length scales, are compared to sticking efficiencies determined through traditional approaches. Force measurement results show that AFM can detect extremely low sticking efficiencies, surpassing the sensitivity of column studies. These data also demonstrate that the 75th to 95th percentile, rather than the mean or median force values, provides a better approximation to values measured in model column experiments or field settings. This variability of the methods provides insight into the fundamental mechanics of microplastic deposition and suggests AFM is isolating the physicochemical interactions, while column experiments also include physical interactions like straining. Advantages of AFM over traditional column/field experiments include high throughput, small volumes, and speed of data collection. For example, at a ramp rate of 1 Hz, 60 sticking efficiency measurements could be made in only a minute. Compared to column or field experiments, the AFM requires much less liquid (μL volume) making it effortless to examine the impact of solution chemistry (temperature, pH, ionic strength, valency of dissolved ions, presence of organics, etc.). Potential limitations of this AFM approach are presented alongside possible solutions (e.g., baseline correction, numerical integration). If these challenges are successfully addressed, then AFM would provide a completely new approach to help elucidate which subsurface minerals represent a sink or temporary storage site for microparticles on their journey from terrestrial to oceanic environments. Full article

Methanol is a liquid fuel with high oxygen content and the potential for a closed-loop carbon-neutral production cycle. To investigate the mixture formation and combustion characteristics of a heavy-duty Port Fuel Injection (PFI) methanol engine, a three-dimensional numerical simulation model was established using the CONVERGE 3.0 software. Multi-cycle simulations were performed to analyze the influence of wall film dynamics on engine performance. The results indicate that the “adhesion–evaporation” equilibrium of the intake port wall film determines the in-cylinder mixture concentration. Due to the high latent heat of vaporization of methanol, severe wall-wetting occurs during the initial cycles, causing the actual fuel intake to lag behind the injection and leading to an overly lean mixture and misfire. Regarding injection strategies, the open valve injection (OVI) strategy utilizes high-speed intake airflow to reduce wall adhesion and improve fuel transport efficiency compared to closed valve injection. OVI refers to the fuel injection strategy that injects fuel into the intake port during the intake valve opening phase. The open valve injection strategy (e.g., SOI −500° CA) demonstrates distinct superiority over closed valve strategies (SOI −200°/−100° CA), achieving a 75% reduction in wall film mass. The long injection duration and early phasing allow the high-speed intake airflow to carry fuel directly into the cylinder, significantly minimizing wall film accumulation and avoiding the “fuel starvation” observed in closed-valve strategies. Additionally, OVI fully utilizes methanol’s latent heat to generate an intake cooling effect, which lowers the in-cylinder temperature and helps suppress knock. Furthermore, a dual-injector strategy is proposed to balance spatial atomization and rapid fuel transport, which achieves a 66.7% increase in the fuel amount entering the cylinder compared with the original strategy. This configuration effectively resolves the fuel induction lag, achieving stable combustion starting from the first cycle. Full article

Most insects secrete special fluids from their tarsal pads which are essential for the function of their attachment systems. Previous studies investigated several physical and chemical characteristics of this pad fluid in different insect species. However, there is not much known about the mechanical properties of fluid from smooth adhesive pads. In this study, we used the stress–relaxation nanoindentation method to examine the viscoelastic properties of pad fluid from Sungaya aeta. Force–displacement and stress–relaxation curves on single fluid droplets were recorded with an atomic force microscope (AFM) and analyzed using Johnson–Kendall–Roberts (JKR) and generalized Maxwell models for determination of effective elastic modulus (E), work of adhesion (Δγ) and dynamic viscosity (η). In addition, we used white light interferometry (WLI) to measure the maximal height of freshly acquired droplets. Our results revealed three different categories of droplets, which we named “almost inviscid”, “viscous” and “rigid”. They are presumably determined at the moment of secretion and retain their characteristics even for several days. The observed mechanical properties suggest a non-uniform composition of different droplets. These findings provide a basis for advancing our understanding about the requirements for adaptive adhesion-mediating fluids and, hence, aid in advancing technical solutions for soft or liquid temporal adhesives and gripping devices. Full article