Search Results (1,983)

High-viscosity sodium alginate solutions (4.5% by mass, apparent viscosity 1 × 10⁴–2 × 10⁴ cP) are widely used in the preparation of hydrogels, wet spinning, and biomedical materials. Residual bubbles can cause internal voids in hydrogels, mechanical heterogeneity, fiber breakage during spinning, and reduced strength, and can severely affect the cell compatibility and clinical safety of biomaterials. Due to the difficulty of bubble migration, coalescence, and rupture in high-viscosity systems, traditional vacuum-standing degassing takes up to 24 h and is extremely inefficient, severely limiting the quality of subsequent processing. To address this issue, this study proposes a novel vacuum-assisted centrifugal recirculating degassing method for highly viscous sodium alginate solutions and aims to establish a kinetic framework for describing its overall degassing behavior. Using the number density of bubbles larger than 0.5 mm in diameter as an evaluation metric, we conducted vacuum-standing control experiments and univariate experiments with different screen mesh apertures (5, 1.5, 0.3, and 0.07 mm). We experimentally verified a continuous kinetic model of bubble number decay based on vacuum bubble expansion, centrifugally enhanced migration, and removal probability during the cycle. The results indicate that the bubble removal effect of 40 min of vacuum–centrifugal cyclic degassing is equivalent to that of 4 h of vacuum static settling, representing a 450% increase in degassing efficiency. There is an optimal range for a screen aperture, with the best degassing effect observed at 0.3 mm, achieving a bubble removal rate of 83.69%. The established kinetic model exhibits good fitting accuracy (RMSE = 0.17, MAPE = 5.9%) and can accurately predict degassing efficiency under different process conditions. This study provides a quantifiable, modelable, and optimizable process scheme for rapid degassing of high-viscosity sodium alginate solutions, and offers a theoretical reference for the development of degassing technologies for high-viscosity polysaccharide fluids. Full article

Electrospinning (ES) can produce nonwoven fibrous mats with high surface area and interconnected porosity, making them attractive for biomedical and functional material applications. However, conventional ES often relies on volatile organic solvents, raising safety, environmental, and translational concerns. Fully aqueous (“green”) ES offers an appealing alternative, although many water-soluble polymers remain difficult to spin and may show limited stability under hydrated conditions. In this study, two fully aqueous binary systems, poly(vinylpyrrolidone)–sodium alginate (PVP–SA) and poly(vinylpyrrolidone)–riboflavin (PVP–RF), were investigated to decouple the roles of sodium alginate (SA) and riboflavin (RF) on solution behaviour, fibre formation, morphology, dry-state mechanical properties, and surface chemistry. Aqueous PVP solutions (20% w/v; molecular weight 1.3 MDa) were blended with SA (1–5 wt% relative to PVP) or RF (1–10 wt% relative to PVP). Electrical conductivity and rheological properties were evaluated prior to ES under controlled conditions, with simultaneous ultraviolet (UV) exposure at 344 nm during fibre collection. RF did not significantly alter conductivity (~0.74–0.75 µS·cm⁻¹), whereas SA increased conductivity up to 2.75 ± 0.03 µS·cm⁻¹ at 5 wt%. All formulations exhibited shear-thinning behaviour, while 10 wt% RF increased the zero-shear viscosity relative to neat PVP. Morphological analysis showed that low SA contents produced uniform fibres, whereas higher SA levels (4–5 wt%) led to bead defects and reduced fibre diameter (down to 85 ± 25 nm). Dry-state mechanical performance decreased with increasing SA content, while 10 wt% RF improved tensile strength and toughness, reaching an ultimate tensile strength of 5.21 ± 0.15 MPa and toughness of 40.51 ± 1.53 MJ·m⁻³. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated subtle UV-driven redistribution of surface chemical states, consistent with mild photo-oxidative microstructural modification rather than extensive covalent network formation. Because the UV irradiance was not directly measured and wet-state stability was not assessed, the UV-related findings are interpreted as preliminary chemical evidence rather than confirmation of stabilized fibre mats. Overall, this work establishes a solvent-free aqueous ES platform in which ionic and photoactive additives can be used to tailor fibre morphology, dry-state mechanical behaviour, and surface characteristics without toxic reagents. Full article

Few strategies have been developed to mimic and control the supramolecular degradations induced by spontaneous fermentation in sour cassava starch, which are partly responsible for its characteristic expansion capacity in breadmaking, and their effectiveness has remained limited. In this context, the objective of this study was to evaluate the effect of adding α-amylase on the functional and nutritional properties of cassava starch used in breadmaking. Cassava starch from the INIAP 651 variety was modified with different α-amylase dosages (0, 2, 4, 6, 8, and 9 U/g α-amylase for 20 min), followed by hydration and pre-gelatinization before baking. Determinations of the specific volume of the bread (SV), dough characterization by Mixolab, pasting properties using a rheometer, and nutritional properties were performed. The treatment with 6 U/g α-amylase showed the best functional properties, achieving the highest SV (4.28 mL/g), C3 (1.67 Nm), C4 (1.11 Nm), and peak viscosity (6550 mPa·s), as well as the lowest setback (1526 mPa·s). In contrast, the treatment with 9 U/g α-amylase exhibited the most favorable nutritional profile, with the lowest estimated glycemic index (51.25) and rapidly digestible starch (15.85 g/100 g). These results confirm that controlled α-amylase dosing modulates cassava starch functionality for breadmaking and glycemic control. Full article

Viscose-derived carbon fibers (VDCFs) are lightweight and flexible textile materials with strong potential for electromagnetic interference (EMI) shielding; however, their performance is governed by surface chemistry. This study aims to tailor the functional properties of VDCFs via process-driven sulfurization. The fibers were treated with sulfur vapor at 400–800 °C under argon, followed by rapid quenching, enabling controlled sulfur incorporation (0.5–12 mmol g⁻¹). Structural and chemical analyses (XRD, SEM–EDS, ATR–FTIR, and TPD–MS) revealed temperature-dependent sulfur incorporation and evolution of sulfur-containing surface functionalities. Sulfurization at 400–500 °C favored the formation of thermally labile sulfur species, tentatively assigned to mercapto-, sulfide-, and polysulfide-type groups, whereas higher treatment temperatures promoted more thermally stable sulfur-containing functionalities associated with the carbon framework. Two desorption regimes (120–250 °C and 250–500 °C) indicate the coexistence of weakly and strongly bound sulfur species. Importantly, sulfurization preserved fibrous morphology while increasing surface roughness and defect density, enhancing interfacial activity. The treatment temperature was identified as the key factor controlling sulfur loading and distribution, with sulfur content continuing to decrease above 600 °C, albeit at a reduced rate. Electromagnetic characterization in the X-band (8–12 GHz) showed a transition toward reflection-dominated EMI shielding, with reflectivity increasing from 87% for pristine fibers to 94–95% for sulfurized samples at 10 GHz, accompanied by corresponding decreases in transmission and absorption. These results demonstrate a clear processing–structure–property relationship and highlight sulfur-functionalized VDCFs as efficient textile components for EMI shielding. Full article

Hydrodynamic cavitation (HC) is an emerging non-thermal technology that is capable of improving the quality and shelf life of fruit juices while retaining heat-sensitive bioactive compounds. This study optimized a mixed-fruit juice (MFJ) blend—60% mandarin, 25% pineapple, and 15% watermelon using a D-optimal mixture design. The MFJ was subjected to HC at varying pressures (4–6 bar) and times (40–60 min) and compared to thermal treatment (90 °C for 30 s). The optimized predicted HC treatment (5 bar/52 min) effectively maintained pH, titratable acidity, and TSS. Notably, HC at 6 bar for 60 min reduced the sedimentation index by 2% and lowered viscosity to 3.56 cP. Compared to thermal processing, the optimized HC-treated sample demonstrated superior nutrient retention, preserving 82.29% of vitamin C, 93.50% of total phenolics, 87.43% of flavonoids, and 61.67% of antioxidant activity. Microbial safety was also improved, achieving a 1.35 log CFU/mL reduction in total plate count and 47.96% peroxidase inactivation. While sensory evaluation showed slightly lower acceptability for HC-treated juice (6.36) versus the control (7.14), it significantly outperformed thermal treatment (3.83). Furthermore, the cavitated sample demonstrated superior bioactive retention after 14 days of storage at 4 °C, with total phenolic content retained at 31.55 ± 0.9 mg GAE/100 mL. The findings suggest that hydrodynamic cavitation can be considered a promising non-thermal processing technology for improving physicochemical stability, preserving bioactive compounds, and extending the shelf life of functional fruit beverages. This underscores HC’s potential as a viable, high-quality alternative to traditional pasteurization in the beverage industry. Full article

The viscosity stability of polymer solution is one of the challenges in enhancing oil recovery, and zwitterionic copolymers present excellent viscosity stability and emulsification performance, enabling effective control of the oil/water interface mobility and enhancing oil recovery. Herein, a zwitterionic copolymer (P(AM/AMBS/MAPTAC)) containing sulfonic acid groups and quaternary amine groups was synthesized by segmentation initiation with AM, AMBS and MAPTAC as monomers. The chemical structure of P(AM/AMBS/MAPTAC) was confirmed by FTIR and ¹H NMR. The M_w value of P(AM/AMBS/MAPTAC) was 9.91 × 10⁶ g/mol, and the apparent viscosity of the 2000 mg/L solution was 24.92 mPa·s at 60 °C at a salinity of 5000 mg/L. P(AM/AMBS/MAPTAC) with sulfonic acid groups and quaternary amine groups exhibited outstanding salt tolerance and shear resistance. When the salinity was 10,000 mg/L and the shear rate was 300 s⁻¹, the apparent viscosity for the P(AM/AMBS/MAPTAC) solution was 23.45 mPa·s and the viscosity reduction rate was 69.23% at 60 °C for 30 d. Moreover, P(AM/AMBS/MAPTAC) exhibited an improved emulsifying property and a greater oil–water interface thickness than HPAM and SPAM due to the synergistic effect of the sulfonic acid and quaternary amine groups in the P(AM/AMBS/MAPTAC) molecule. The polymer flooding and alkali–surfactant–polymer flooding formed by P(AM/AMBS/MAPTAC) had high chemical oil recovery, and the oil displacement efficiency of P(AM/AMBS/MAPTAC) was higher than that of HPAM and SPAM in the polymer flooding and alkali–surfactant–polymer flooding systems. Full article

Hydraulic fracture height growth in thin sandstone–mudstone interbeds is often limited by bedding interface failure and multi-cluster stress interference. In this study, a coupled fracture–matrix interface finite element model was developed for the He-8 sandstone–mudstone interbeds in the Sulige Gas Field and validated against previously published true triaxial hydraulic fracturing experiments. The simulations indicate that vertical–horizontal stress difference (VSD; the difference between overburden stress and minimum horizontal stress within a layer) promotes fracture-height growth, whereas interlayer stress difference (ISD; the minimum horizontal stress contrast between adjacent layers) acts as a stress barrier that promotes bedding interface shear failure and arrests vertical growth. For the investigated reservoir configuration, each 4 MPa increase in VSD increased fracture height by approximately 1.5 m in the three-cluster case and 1.8 m in the four-cluster case, whereas each 2 MPa increase in ISD reduced the average fracture height by approximately 4.0 m in the three-cluster case and 3.5 m in the four-cluster case. Under moderate ISD, increasing the fluid viscosity was more effective than increasing the injection rate alone, although the benefit depended on cluster number and interface failure state. These results clarify how stress contrast, interface strength, and multi-cluster stress shadows jointly control cross-layer fracture propagation in thin interbedded reservoirs. Full article

Gelatin is a valuable hydrocolloid produced by partial hydrolysis of collagen from mainly mammalian and fish sources. The rheological properties of fish gelatin differ from those of mammalian species in terms of gel strength, viscosity, and other rheological characteristics, even from different fish species and parts of the fish with different properties. Fish gelatin is sustainable for the environment and easy for people to accept for cultural reasons. Owing to these properties, gelatin is used across food, biomedical, pharmaceutical, and health sectors, where 3D printing enables customization and functional performance. Key determinants of print fidelity include gelatin concentration, rheological properties, temperature, gelling behavior, water content, and printing parameters. Suitability for 3D printing is typically assessed via physicochemical characterization, particularly rheology and gelling mechanisms/kinetics. Gelatin-based 3D printing systems offer various advantages due to their biocompatibility, low cost, and controllable rheological properties, and they have potential applications in the food, healthcare, biomedical, tissue engineering, and drug delivery system areas. Using gelatin in combination with other additives can improve printing accuracy and mechanical strength parameters, overcome the limitations of gelatin’s inherent mechanical strength, and develop higher printing accuracy and performance systems. This allows for the development of functional, innovative, and high-value-added products while ensuring safe use. Full article

Modulating the physical crosslink architecture of gelatin methacryloyl (GelMA) hydrogels without altering total polymer concentration or introducing exogenous components remains a central challenge in biomaterial design. Here, we present a source blending strategy in which porcine skin gelatin (PG) and salmon skin gelatin (SG), two gelatins with markedly different proline and hydroxyproline contents, are combined at seven compositional ratios (PG weight fractions 0–1.0) and subsequently functionalized to GelMA under standardized conditions (8% v/v methacrylic anhydride, 60 °C, 3 h). Near-complete degrees of substitution (95–98%) were achieved across all formulations, as confirmed by both TNBS and ¹H-NMR analyses. In the parent gelatin mixtures, increasing PG fraction progressively increased viscosity, elastic modulus (G′), gelation temperature (Tgel), and compression modulus at 4 °C, with DSC revealing independent SG (0–15 °C) and PG (20–40 °C) endothermic transitions that suggest partial hindrance of PG triple-helix formation by high SG fractions. These composition-dependent trends were preserved after functionalization to GelMA, albeit with attenuated physical crosslinking due to steric impairment by the methacrylate groups. Photocrosslinked GelMA hydrogels fabricated after pre-incubation at 4 °C exhibited systematically higher compression moduli and lower swelling degrees with increasing PG content, demonstrating that the PG/SG ratio provides an effective means for independently tuning hydrogel mechanics and mesh architecture. In vitro release assays using Rhodamine 6G further demonstrated that pre-incubation at 4 °C prior to photocrosslinking effectively modulates transport kinetics in SG-PG GelMA hydrogels. This strategy delayed characteristic release times and constrained Weibull shape parameters to the anomalous-transport regime (0.75 < β < 1), where diffusion is governed by network chain relaxation. This effect was most pronounced in the 0.4SG:0.6PG formulation, where lower SG content permitted unhindered triple-helix formation, as corroborated by DSC and compression studies. Ultimately, adjusting the pre-incubation temperature and gelatin source combination provides a straightforward, processing-additive-free strategy to achieve programmable release profiles via controlled matrix tortuosity. Full article

This article describes the development of a compact and affordable variable-temperature NMR instrument designed primarily to measure dynamic molecular motion in solids and liquids. The instrument consists of Lab-Tools’ Mk4 palm-top time-domain NMR spectrometer fitted with a Peltier-cooled variable-temperature probe inside a shimmed Halbach magnet. Measurement of NMR relaxation times T₁, T₂, and ${\mathrm{T}}_1\rho$ is possible over the temperature range −20 °C to 70 °C with cooling and heating rates, and data acquisition is controlled from an integrated mini-PC. The overall footprint of the instrument is roughly that of a shoe box, making both in-the-field and bench-top measurements possible. Applications of this instrument include measuring pore-size distribution in porous rocks, the viscosity of oils and tars trapped in porous rock, the properties of polymers, and the viscosity of the liquid components of foods (e.g. fruits, vegetables and seeds). Results of test measurements for calibrated oils and olive oil are presented together with measurements of molecular mobility in a solid polymer. Full article

High-temperature temporary sealing operations require liquid plug materials that can be placed as low-viscosity precursors, converted into mechanically stable networks under reservoir temperature, and subsequently removed after service. Existing epoxy-based sealing systems generally provide high post-curing strength, but the coordination among pumpability, thermally triggered curing, and post-service degradability remains insufficiently addressed. In this work, an epoxidized soybean oil (ESO)-modified epoxy–anhydride liquid plug was designed to regulate these sequential stages within a single material system. The precursor formulation, rheological transition, curing kinetics, mechanical response, network structure, and degradation behavior were evaluated using viscosity monitoring, curing-time tests, DSC, compression testing, DMA, gel fraction and swelling measurements, FTIR, and high-temperature degradation experiments. The optimized precursor exhibited an initial viscosity of 65.4 ± 2.1 mPa·s, remaining below the pumpability threshold of 100 mPa·s before curing. Its curing time was adjustable within 1–10 h at 120–140 °C through temperature and initiator regulation. ESO incorporation produced a non-monotonic mechanical response, with the optimized network reaching a compressive strength of 112.5 ± 3.5 MPa and an elastic modulus of 142.50 ± 5.26 MPa. FTIR and thermal–mechanical analyses supported the formation of an ester-rich epoxy–anhydride network containing both rigid epoxy-derived segments and ESO-derived flexible chains. In the post-service stage, degradation was strongly temperature dependent, with the characteristic unsealing time decreasing from 84 h at 120 °C to 24 h at 130 °C and 18 h at 140 °C. The combined results define a coupled curing–degradation window in which pumpable placement, thermal network formation, load-bearing sealing, and controlled unsealing are temporally separated but structurally connected. Full article

Rice starch (RS) is widely consumed, but is usually rapidly digested, which may increase postprandial blood glucose levels. Therefore, regulating RS digestibility is important for development functional starch-based foods. In this study, sodium alginate (NaAlg) was incorporated into RS gels and subsequently crosslinked with Ca²⁺ to form a calcium alginate (CaAlg) network, and its effects on the physicochemical properties, digestion behavior, and physiological responses of RS gels were evaluated. Rheological measurement showed that the Ca²⁺-crosslinked alginate network increased the viscosity and viscoelastic moduli of RS gels. Low-field nuclear magnetic resonance analysis showed that the Ca²⁺-crosslinked alginate network reduced free water mobility. Structural characterization using Fourier-transform infrared spectroscopy, X-ray diffraction, and cold-field scanning electron microscopy shows that the Ca²⁺-crosslinked alginate network was associated with enhanced intermolecular interactions and a more continuous gel network, while all gelatinized samples exhibited predominantly amorphous structures. In vitro digestion experiments showed that the hydrolysis degree at 120 min decreased from 92.3% in RS to 85.6% in HCaAlg/RS. The rapidly digestible starch content significantly decreased from 72.4% to 68.4% (p < 0.05), while resistant starch significantly increased from 7.7% to 14.4% (p < 0.05). First-order kinetic fitting showed that C_∞ significantly decreased from 93.0% to 86.0%, and k significantly decreased from 0.027 to 0.013 min⁻¹ (p < 0.05). In vivo experiments showed that the Ca²⁺-crosslinked alginate/RS gels were associated with a lower postprandial glycemic response, with the incremental area under the curve significantly decreased from 747.2 to 591.7 mmol·min/L (p < 0.05), and the intestinal propulsion rate decreased from 89.6% to 75.3% (p < 0.05). These results suggest that Ca²⁺-crosslinked alginate network formation may modulate the structural properties, digestion behavior, and digestion-related physiological responses of RS gels, providing a basis for the development of starch-based functional foods with improved glycemic control. Full article

This study investigates non-isothermal laminar flow of waxy crude oil in a pipe. Due to heat exchange with the surroundings, the flow cools along the pipe length, resulting in a gradual transformation of the oil rheology from Newtonian to viscoplastic behavior. The mathematical model is based on the generalized Navier–Stokes equations coupled with the Shvedov–Bingham rheological model and the effective viscosity approach. The governing equations were solved numerically using the control volume method in the velocity–pressure formulation. The numerical simulations produced velocity, temperature, and effective viscosity fields, as well as pressure-drop data characterizing the rheological state of the waxy crude oil throughout the pipe flow domain. It was established that, in the central region of the inlet flow, the oil retains Newtonian behavior, whereas viscoplastic behavior begins to develop near the pipe wall. Further downstream, the flow progressively transforms into a viscoplastic state over the entire pipe cross-section, accompanied by the formation of stagnant near-wall regions and a plug-flow core. Full article

Background: Oxidative stress contributes significantly to premature skin aging and inflammatory dermatological conditions. While plant-derived antioxidants have demonstrated considerable promise in topical applications, Bougainvillea glabra Choisy remains underexplored in standardized pharmaceutical dosage form development despite its documented phytochemical richness. Objective: This study aimed to develop, standardize, and characterize topical cold cream formulations incorporating B. glabra ethanolic leaf extract, with HPTLC-based quantification of marker compounds, validated antioxidant assessment, and preliminary dermal safety evaluation. Methods: The ethanolic leaf extract was prepared by maceration and characterized by preliminary phytochemical screening and HPTLC fingerprinting with quantitative densitometric analysis of quercetin and pinitol. Three cold cream formulations were developed at 10% (F1), 20% (F2), and 30% (w/w) (F3) extract loading. Formulations were evaluated for organoleptic properties, pH, homogeneity, spreadability, and viscosity. Antioxidant activity was assessed using a validated methanol extraction procedure followed by DPPH radical scavenging and potassium permanganate reduction assays. Ex vivo skin permeation was evaluated using Franz diffusion cells with freshly excised goat skin. Accelerated stability was conducted at 40 ± 2 °C/75 ± 5% RH for 90 days with HPTLC-based marker retention monitoring. Primary dermal safety was assessed in Wistar albino rats (n = 6) following OECD Test Guideline 404. Results: Quantitative HPTLC confirmed quercetin (4.82 ± 0.14 mg/g dry extract) and pinitol (2.31 ± 0.09 mg/g) as marker compounds, with linearly increasing content across F1–F3. All formulations demonstrated acceptable physicochemical properties (pH 5.7–5.9, viscosity 440,000–460,000 cP, spreadability 11.8 ± 0.3 cm·g/s). F3 exhibited the highest DPPH scavenging activity (56.68 ± 1.05%) with IC₅₀ of 1.3 ± 0.1% w/v, demonstrating a 3.2-fold improvement over F1. Extraction recovery from the cream matrix was 96.4–97.1%, validating the antioxidant data. Ex vivo quercetin permeation through goat skin reached 51.3 ± 2.8 μg/cm² at 24 h for F3, following Higuchi diffusion kinetics (R² > 0.99). No dermal irritation was observed (Primary Irritation Index = 0). Accelerated stability confirmed ≥98.3% retention of both marker compounds and antioxidant activity after 90 days. Conclusions: B. glabra leaf extract was successfully incorporated into a physicochemically stable, non-irritating cold cream with demonstrated dose-dependent antioxidant efficacy and cutaneous delivery capability. The study establishes preliminary dermal safety and in vitro antioxidant efficacy warranting further controlled clinical evaluation. Full article

This study investigated the influence of carrot cryopowder, obtained by cryogenic grinding, on the rheological, physicochemical, and structural characteristics of a structured curd product. The experiment was conducted using a three-factor Box–Behnken design, varying the mass fraction of curd (70–90%), carrot cryopowder content (2–6%), and fat content in cream (7–33%). Viscosity values ranged from 914 to 2810 mPa·s, with the highest value of (2810 mPa·s) recorded in experimental sample No. 5. The best overall characteristics were observed in this sample, which showed a β-carotene content of 2.76 ± 0.03 µg/g, while the concentrations of vitamins B1, B2, B3, B5, B6, and folic acid were 20–31% higher compared to the control sample. The regression model (R² = 0.9164) identified the optimal formulation: 89.6% curd, 5.4% carrot cryopowder, and 31.3% fat in cream. Storage stability studies conducted over 28 days at 4 ± 1 °C demonstrated additional practical advantages. The addition of carrot cryopowder significantly reduced syneresis to 12.4 ± 1.1% on day 28 (compared to 28.7 ± 2.3% in the control), improved microbiological stability, and maintained acceptable sensory properties with an overall acceptability score of 6.8 ± 0.6 points after 28 days. FTIR analysis confirmed that the carrot cryopowder was not merely mechanically dispersed within the matrix but actively participated in the formation of new intermolecular interactions, leading to the modification of the product’s chemical structure. The obtained results showed that the incorporation of carrot cryopowder not only increased the nutritional and functional value of the curd product but also enhanced its structural stability and potential shelf life without negatively affecting the main technological indicators. Full article