Viscosity Measurements Research Articles

Formulation and Physicochemical Evaluation of Spray Gel Containing Cordyline fruticosa L. Leaf Extract for Topical Delivery

Spray gel is a gel system applied through a spray pump, producing small or large liquid droplets. Cordyline fruticosa (L.) A. Cheval, commonly known as Andong Merah, is a plant with various medicinal properties, including wound healing activity attributed to its flavonoid content. This research aimed to formulate and evaluate the physicochemical properties of a spray gel containing Cordyline fruticosa leaf extract for topical delivery, focusing on the effects of different concentrations of Carbopol 940 as a gelling agent and sorbitol as a humectant. Cordyline fruticosa leaf extract was obtained by maceration using 96% ethanol. Three spray gel formulations were prepared, varying the concentrations of Carbopol 940 (0.4 g, 0.6 g, and 0.8 g) and sorbitol (5 ml, 7.5 ml, and 10 ml). The prepared spray gels were then subjected to physicochemical evaluation, including organoleptic tests (color, odor, and consistency), homogeneity tests, pH measurements, viscosity measurements, spray pattern analysis, and adhesion tests. All spray gel formulations exhibited acceptable physicochemical properties. The formulations were homogeneous, with a pH within the acceptable range for topical applications. The viscosity and adhesion properties varied with the concentrations of Carbopol 940 and sorbitol. The spray pattern analysis revealed a circular spread pattern, with the pressure required for spraying influenced by the viscosity of the formulation. The spray gel formulations containing Cordyline fruticosa leaf extract demonstrated good physicochemical qualities, indicating their potential suitability for topical delivery. Further studies are recommended to optimize the formulation for enhanced stability and therapeutic efficacy.

Optimizing in-situ upgrading of heavy crude oil via catalytic aquathermolysis using a novel graphene oxide-copper zinc ferrite nanocomposite as a catalyst

Unconventional resources, such as heavy oil, are increasingly being explored and exploited due to the declining availability of conventional petroleum resources. Heavy crude oil poses challenges in production, transportation, and refining, due to its high viscosity, low API gravity, and elevated sulfur and metal content. Improving the quality of heavy oil can be achieved through the application of steam injection, which lowers the oil’s viscosity and enhances its flow. However, steam injection alone falls short of meeting the growing demand for higher-quality petroleum products. Catalytic upgrading is therefore being investigated as a viable solution to improve heavy oil quality. This study experimentally investigates the application of two novel catalysts, namely copper-substituted zinc ferrite (ZCFO) synthesized via the sol–gel combustion method and a graphene oxide-based nanocomposite (GO-ZCFO) with different ratios, for catalyzing aquathermolysis reactions in the steam injection process, with the aim of enhancing the in-situ upgrading of heavy oil. These catalysts underwent characterization using X-ray powder diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Transmission Electron Microscopy (TEM). Their catalytic performance was assessed utilizing a high-pressure/high-temperature reactor (300 ml), with a comprehensive analysis of the changes in the physical and chemical properties of the heavy oil before and after upgrading. This analysis included measurements of sulfur content, SARA fractions, viscosity, API gravity, and Gas Chromatography (GC) of saturated hydrocarbons and evolved gases. All upgrading experiments, including both catalytic and non-catalytic aquathermolysis processes, were conducted under a reaction time of 6 h, a reaction temperature of 320 °C, and high pressure (86–112 bar). The results indicated that the introduction of the proposed catalysts as additives into the upgrading system resulted in a significant reduction in sulfur content. This, in turn, led to a decrease in resin and asphaltene content, an increase in the content of saturated hydrocarbon, particularly low-molecular-weight alkanes, and ultimately, a reduction in viscosity along with higher API gravity of the crude oil. GO-ZCFO with a weight ratio (50:50) exhibited the best catalytic performance. The heavy crude oil, upgraded with this 50:50 ratio, exhibited significant enhancements, including a 29.26% reduction in sulfur content, a 21.27% decrease in resin content, a 37.60% decrease in asphaltene content, a 46.92% increase in saturated hydrocarbon content, a 66.48% reduction in viscosity, and a 25.49% increase in API gravity. In comparison, the oil upgraded through non-catalytic aquathermolysis showed only marginal improvements, with slight reductions in sulfur content by 5.41%, resin content by 3.60%, asphaltene content by 11.36%, viscosity by 17.89%, and inconsiderable increases in saturated hydrocarbon content by 9.9% and API gravity by 3.02%. The GO-ZCFO, with its high catalytic activity, stands as a promising catalyst that contributes to improving the in-situ upgrading and thermal conversion of heavy crude oil.

Study on interfacial tension, wettability and viscosity in different salinities of synthesized a new polymeric surfactant for improving oil recovery

Over 50% of the original oil in place (OOIP) is immobile or trapped in the reservoir. Therefore, today, more efficient methods have been introduced in the tertiary oil recovery sector as a scheme of enhanced oil recovery (EOR). Due to the decline of conventional hydrocarbon reserves, polymers are increasingly used in EOR methods, such as surfactant-polymer (SP) and alkaline-surfactant-polymer (ASP) flooding. SP flooding has a complex formulation and design, leading to undesirable phase separation if improperly mixed. Polymeric surfactants are a promising alternative to SP flooding. They consist of hydrophobic groups attached to hydrophilic polymers, which help to improve the mobility ratio and reduce interfacial tension (IFT). This paper examines the rheological and synthesis properties of a new polymeric surfactant produced through bond co-polymerization reaction using different hydrolyzed polyacrylamide (HPAM) ratios and a zwitterion hydrophobic group. The synthesized hydrophobically modified zwitterionic polyacrylamide (HMZPAM) was characterized by FTIR and HMNR analysis. HMZPAM performed better than other substances in IFT, viscosity, wettability, oil recovery, and resistance to different one and two-valence cations. The results indicate that HPAM reduced the IFT to 13.65, while HMZPAM reduced it to 0.441 mN/m. Wettability change evaluated on a rock carbonate/crude oil/HMZPAM system that changed the water-wet state of the primary oil-wet rock carbonate to strongly water-wet state as wettability change measurements showed a decrease in contact angle from 62.76 to 21.23 degree. Comparative studies on the effectiveness of HPAM and HMZPAM were also conducted according to the measurement of viscosity and shear rate in the presence of salt, which indicates the higher shear rate and viscosity of HMZPAM. Core flooding tests revealed that HMZPAM resulted in better additional recovery due to microscopic displacement, resulting in a total oil recovery of 84%, compared to 48% of residual oil saturation for HPAM. Also, salts decreased oil recovery in HPAM injection but increased oil recovery in HMZPAM injection.

Co(II), Ni(II), and Cu(II) Ternary Complexes With 2,6‐Pyridinedicarboxylic Acid and 2,2′‐Bipyridyl: Synthesis, Characterization, DNA Binding, Photo‐Cleavage, and Antimicrobial Studies

ABSTRACTThe interaction of 2,6‐pyridinedicarboxylicacid (PDA) and 2,2′‐bipyridyl (Bipy) with Co(II), Ni(II), and Cu(II) ions produced new ternary complexes [M (PDA)(Bipy)(H2O)] (M = Co(II), Ni(II), and Cu(II)), which were studied by elemental, spectral (FT‐IR, Mass, UV–Vis), and thermal analysis, and their interaction with Ct‐DNA was thoroughly studied using various methods, including absorption spectroscopy, fluorescence spectroscopy, and viscosity measurements. Spectrophotometric titration and viscosity measurements indicated that all the complexes bind to DNA via the groove mode of binding. The salt‐dependent binding of ternary metal complexes to Ct‐DNA has been studied by a UV–Vis spectrophotometric titration experiment. Furthermore, photocleavage studies were used to examine how the metal complexes interacted with the pBR322 DNA, and the results proved that these compounds have obvious photo cleavage properties. The biological effects were studied by antibacterial activity.

Into the Groove: A Multitechnique Insight into the DNA–Vemurafenib Interaction

This study explores the interaction between Vemurafenib (VEM), a potent BRAF inhibitor, and calf thymus DNA (ctDNA) using a comprehensive array of biophysical and computational techniques. The primary objective is to understand the potential off-target effects of VEM on DNA, given its established role in melanoma therapy targeting the BRAF V600E mutation. The investigation employed methods such as ultraviolet–visible absorption spectroscopy, steady-state fluorescence, circular dichroism, isothermal titration calorimetry, and advanced molecular dynamics simulations. The results indicate that VEM interacts with DNA primarily through a minor groove-binding mechanism, causing minimal structural disruption to the DNA double helix. Viscosity measurements and melting temperature analyses further confirmed this non-intercalative mode of binding. Calorimetry data revealed an exothermic, thermodynamically favorable interaction between VEM and ctDNA, driven by both enthalpic and entropic factors. Finally, computer simulations identified the most probable binding site and mode of VEM within the minor groove of the nucleic acid, providing a molecular basis for the experimental findings.

A comparative study of blood viscometers of 3 different types.

The greater the viscosity of the blood, the more difficult its flow becomes, leading to an increased incidence of diseases caused by blood circulation disorders. These diseases are commonly associated with the cardiovascular and cerebrovascular systems. High blood viscosity is a primary cause of circulatory system diseases. Studies have shown that accurately measuring blood viscosity and applying this data in clinical trials can help prevent circulatory system diseases. Viscosity data can vary depending on the measurement methods used, even when these methods are based on hydrodynamic principles. Despite using approved blood viscometers, the results often differ depending on the type of viscometer used, potentially causing confusion within the medical field. Informing the medical community about these differences and the level of error associated with each measurement method can help reduce this confusion. To our knowledge, the degree of difference in viscosity measurement results due to different measurement methods and the reasons for these differences have not yet been thoroughly explored. In this study, we selected three blood viscosity measurement methods registered with the Ministry of Food and Drug Safety of Korea to analyze the same canine blood. The viscosity measurements were carried out using each device and compared. The parallel plate and scanning capillary methods yielded similar viscosity values, while the cone plate method showed lower viscosity values. The viscosity of blood, as measured by the three viscometers, differed, indicating that more experimental data must be accumulated to evaluate the cause of these differences. In this paper, we identified several causes of inconsistency and suggested measures to avoid this confusion. However, confirming that the test results show systematic differences is expected to assist clinicians who diagnose and prescribe treatments based on blood viscosity results. The findings of this comparative study are anticipated to serve as a starting point for establishing guidelines or standards for blood viscosity measurement methods.

Effect of Fucoidan on Conformation of Xanthan Gum and Its Tribo-Rheological Properties.

This study sought to explore the rheological and tribological properties of fucoidan-xanthan gum (XG) mixtures at different fucoidan concentrations. A conformational transition of XG from disordered to ordered forms was observed with an increasing fucoidan concentration, as determined by intrinsic viscosity measurements and Fourier transform infrared analysis. All mixtures exhibited non-Newtonian flow behavior with the yield stress. The mixture sample with 0.5% fucoidan displayed higher apparent viscosity at 100 s-1, yield stress, and viscoelastic moduli values than XG alone, suggesting viscoelastic synergism between the two biopolymers. However, these values exhibited a decreasing trend with higher fucoidan concentrations (0.5-2.0%), indicating a nullification of synergism. While XG alone exhibited antithixotropic behavior, fucoidan-XG mixtures showed thixotropic behavior, most pronounced at 1.0% fucoidan. A decreasing trend was observed in the maximum friction coefficient as the fucoidan concentration increased, indicating better lubricant properties. Collectively, our findings may enable widespread adoption and application of fucoidan in various industries.

Increasing LNAPL density and viscosity are indicators of Natural Source Zone Depletion

Natural source zone depletion (NSZD) acts to reduce the mass and/or toxicity of light non-aqueous phase liquids (LNAPL) in the shallow subsurface. Several indirect measurement techniques are commonly used to estimate LNAPL mass depletion based on CO 2 generation by hydrocarbon mineralisation, heat production by exothermic biodegradation processes, and sub-surface gas concentration gradients. This paper presents data on LNAPL density and viscosity and shows changes that result from NSZD processes. Increasing trends in LNAPL density and viscosity were observed that provided a qualitative line-of-evidence for NSZD. When LNAPL density and viscosity were combined with contemporaneous LNAPL chemistry analysis it was possible to correlate changes in the physical properties to depletion of alkanes from the LNAPL in a manner that would inform a quantitative NSZD assessment. LNAPL density and viscosity measurements are relatively cheap and reproducible, and increasing trends in LNAPL density and viscosity provide additional lines-of-evidence for NSZD.

Charge Mediated Changes to the Intrinsic Viscosity of Biopolymer Systems

A theoretical approach is presented to quantify the effect of ionic strength on the swelling and shrinkage of the hydrodynamic coil size of a generic biopolymer. This was conducted in view of extraction methods that often utilize acids and alkali combinations and, therefore, invariably impact the levels of salt found in commercially available biopolymers. This approach is supplemented by intrinsic viscosity measurements for the purpose of validation across a variety of biopolymer architectures, type of functionalization, as well as the quoted molar mass. By accurately capturing the magnitude of change in the coil size, it is discussed how a biopolymer coil size is far more sensitive to changes in the ionic strength than it is to the molar mass (or contour length) itself. In turn, it is highlighted why the current characterization strategies that make use of weight-averaged molar mass are prone to errors and cannot be used to establish structure—property relationships for biopolymers. As an alternative, the scope of developing an accurate understanding of coil sizes due to changes in the “soft” interactions is proposed, and it is recommended to use the coil size itself to highlight the underlying structure—property relationships.

Synthesis, cytotoxicity, docking, MD simulation, drug-likeness, ADMET prediction and multi spectroscopic studies of some novel quinoline-4-carboxamide derivatives as DNA intercalating and anticancer agents

In this study, some new quinoline-carboxamide derivatives possessing a flexible (dimethylamino) ethylcarboxamide side chain were synthesized as DNA intercalating agents. Synthesized compounds displayed potent cytotoxic activities against three human cancer cell lines including colorectal adenocarcinoma cancer cells (HT-29), breast cancer cells (MCF-7) and lung cancer cells (A549). Compound 3d showed promisingantiproliferative activity (IC50= 3.97 to 6.67 µM) against cancer cells. The simplest compound (compound 3a) without substitution displayed the weakest cytotoxic effects ranging from 24.6 to 42.3 μM. The interaction of the most cytotoxic compound 3d with calf thymus DNA (ctDNA) was evaluated by fluorescence, UV absorption, resonance light scattering (RLS), melting studies, viscosity measurements, circular dichroism (CD) spectroscopy, molecular docking and molecular dynamic (MD). Generally, studies displayed a combined quenching via intercalating binding mode of compound 3d to ctDNA.

Characterization of the dynamic viscosity of cell cultures and its effect on mixing performance in a spinner flask bioreactor

Computational fluid dynamics (CFD) models have been developed to simulate cell culturing bioreactors but assume water-like viscosity properties due to significant data gaps. This study characterized the dynamic viscosity of HEK-293 cell cultures and evaluated its effect on mixing performance in a spinner flask bioreactor. Viscosity measurements indicated that the cell culture media, media with microcarriers, and cell cultures presented shear thinning behaviors within the measured shear rate range of 1–100 s−1. The viscosity also increased with the microcarrier concentrations and growth of cell culture. The CFD model, incorporating dynamic viscosity data, showed that shear stress and Kolmogorov length profiles are significantly influenced by microcarrier concentrations and cell culture growth. Higher microcarrier concentrations led to higher average shear stress and Kolmogorov values. The cultured HEK-293 cells after seven days of growth also had higher average shear stress and Kolmogorov values than at the day of seeding, indicating an impact caused by the cells’ metabolism and biomass. Overall, the results indicated that assuming water-like properties underestimates shear stress and Kolmogorov length scales, especially at zones of lower shear rates due to the observed shear thinning behavior. Thus, careful monitoring of dynamic viscosity of cell cultures and proper control of mixing parameters are critical to deliver the desired mixing conditions for optimized cell growth especially during scale-up production operations.

Palladium(II) and platinum(II) thiophene-based thiosemicarbazones: Synthesis, properties, and anticancer studies

The aim of this study was to synthesize and investigate the cytotoxic profile of four palladium(II) and two platinum(II) complexes containing thiosemicarbazones derived from thiophene against tumor cells. They were fully characterized by various analytical techniques, including 1H, 13C{1H}, 31P{1H}, 135DEPT NMR, IR, UV–vis, X-ray diffraction, molar conductivity, and theoretical. Several techniques were used to evaluate the interaction of the complexes with DNA, such as gel electrophoresis, UV–vis spectroscopy, circular dichroism, viscosity measurements, fluorescence assay with Hoescht 33,258, and molecular docking. The results indicated that the complexes exhibited electrostatic and/or groove interaction with DNA, but only at high concentrations (100 µM). In vitro, cytotoxicity assays were performed using the MTT method, and the palladium(II) complexes showed remarkable cytotoxic activity against A549 and A2780cis cell lines. In particular, the PdT compound showed cytostatic behavior against the A549 tumor line, while the PdCH3 compound showed cytotoxic behavior against the A2780cis line. Further investigation of the most promising compound, PdCH3, in A2780cis revealed that it induced apoptosis by promoting cell accumulation in the sub-G1 phase and causing partial mitochondrial membrane depolarization. In addition, this complex significantly inhibited colony formation, leading to significant changes in cell morphology. However, no inhibition of cell migration was observed in the 3D cell model of DAOY cells. These findings provide valuable insights and structural features for the design of selective palladium complexes targeting ovarian tumor cells (A2780cis). The study highlights the potential of these complexes as cytotoxic agents against specific cancer cell lines, paving the way for future advances in medicinal chemistry research.

Sub-Ambient Performance of Potassium Sarcosinate for Direct Air Capture Applications: CO2 Flux and Viscosity Measurements

Absorption based direct air capture (DAC) technologies have garnered significant interest in recent years due to their scalability, competitive regeneration energy requirements, and low susceptibility to degradation. One of the key advantages of DAC lies in its flexible siting options and the potential to utilize low-value land. However, most of the research in this field has been focused on ambient climate zones (T > 20 °C), overlooking sub-ambient (−30 °C < T < 20 °C) regions, which comprise approximately 70 % of the Earth’s surface. To fully realize the potential of DAC, it is essential to understand how DAC solvents perform in these sub-ambient conditions before any large-scale deployment can be considered. Among DAC solvents of interest, potassium sarcosinate (K-SAR) has emerged as a promising candidate due to its high CO2 capacity, fast uptake kinetics, compatibility with contactor packing materials, low volatility, good thermal and oxidative stability, and competitive regeneration energy requirements compared to current industry standards. This paper characterizes the CO2 flux and viscosity of K-SAR at sub-ambient conditions and explores the potential of using ethylene glycol and triethylene glycol as additives to prevent solvent freezing in DAC applications. For 1 M K-SAR, the CO2 flux ranges between 1.3 × 10-5 and 8.0 × 10-5 mol m−2 s−1 across a temperature range of −5 °C to 45 °C. Ethylene glycol is shown to effectively suppress the freezing point of K-SAR below −30 °C with volumetric loadings of the additive as low as 0.1. A reaction model was developed to predict the CO2 flux for 1 M K-SAR at different temperatures, demonstrating good agreement between experimental and theoretical fluxes.

Removal of acetyl-rich impurities from chitosan using liquefied dimethyl ether

Chitosan, recognized for its excellent biodegradability, biocompatibility, and antibacterial properties, has several potential applications, particularly in the biomedical field. However, its widespread use is hindered by inherent limitations such as low mechanical strength and safety concerns arising from a low degree of deacetylation and the presence of impurities. This study aimed to introduce an innovative purification method for chitosan via liquefied dimethyl ether (DME) extraction. The proposed technique effectively addresses the challenges associated with chitosan by facilitating deacetylation and impurity removal. Liquefied DME is emerging as the extraction solvent of choice owing to its advantages, such as low boiling point, safety, and environmental sustainability. The degree of deacetylation of chitosan was extensively evaluated using thermogravimetric–differential thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction, intrinsic viscosity measurements, solid-state nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy, and elemental analysis. The solubility of chitosan in liquefied DME was investigated using Hansen solubility parameters. This study contributes to the improvement of the safety profile of chitosan, thereby expanding its potential applications in various fields. The use of liquefied DME as an extraction solvent proved to be efficient in addressing the existing challenges and is consistent with the principles of safety and environmental sustainability.

Combined optical measurement of dissolved oxygen tension (DOT), pH value, biomass and viscosity in shake flasks

Shake flasks are widely spread in microbial process development. Characterization of the processes by manual offline sampling is time-consuming, highly laborious and a contamination risk. Online monitoring of key parameters would provide deeper insights, while saving time and effort. In this study, a device for optical online monitoring of dissolved oxygen tension (DOT), biomass, pH value and viscosity in shake flasks is presented. DOT measurement relies on fluorescent oxygen sensitive nanoparticles. The fluorescence intensity signal of the nanoparticles is used to trigger the DOT and scattered light measurements inside the rotating bulk liquid. The scattered light signal (610 – 630 nm) can be correlated to offline measured optical density OD600, even at elevated viscosity. The pH value is monitored online by using pH sensor spots, fixed inside the shake flasks. The shift of the angle of the bulk liquid Θ-Θ0 is correlated to the offline measured viscosity. Detection of the leading edge of the bulk liquid, necessary for viscosity measurement, can be performed either using the fluorescence intensity signal of the oxygen nanoparticles or the scattered light signal.

Tribological performance of used engine oil treated with cement and celite adsorbents by solvent extraction-adsorption method

Purpose As lubricating oils are used, their performance deteriorates and they become contaminated. The purpose of this paper is to investigate the lubrication performance of reclaimed 5 W-30 a fully synthetic used engine oil (UEO) with wear tests after refining it from a solvent-based extraction method using solvent (1-PrOH) and adsorbent materials such as cement, celite and deep eutectic solvent (DES). Design/methodology/approach The treated oil mixtures were prepared by blending engine oils with various adsorbent materials at 5% (w/w) in organic 1-PrOH solvent at a UEO: solvent ratio of 1:2 (w/w). The measurement of kinematic viscosity, density, the total acid number (TAN) and elemental analysis of oil samples was done by the ASTM standards D445/D446, D4052, D974 and D6595, respectively. Adsorbents and treated oil samples characterized by SEM-EDX, FTIR and UV analysis, respectively. Meanwhile, lubricating performance in tribological applications was evaluated through the wear test device using a rotating steel alloy 1.2379 cylinder and a stationary 1.2738 pin under 20, 40 and 80 kg load conditions. Worn surface analysis was done with SEM and 2.5D images. Findings It was found that when using the combination of cement and celite as an adsorbent in the reclamation of used engine oil demonstrated better lubricant properties. The properties of used engine oil were improved in the manner of kinematic viscosity of 32.55 from 68.49 mm2/s, VI (Viscosity index) value of 154 from 130, TAN of 3.18 from 4.35 (mgKOH/g) and Fe content of 11 from 32 mg/L. The anti-wear properties of used engine oil improved by at least 32% when 5% cement and 5% celite adsorbent materials were used together. Research limitations/implications The paper is based on findings from a fully synthetic 5 W-30 A5 multi-grade engine lubrication oil collected after driving approximately 12.000 km. Practical implications The results are significant, as they suggest practical regeneration of used engine oil is achievable. Additionally, blending fresh oil with reclaimed used engine oil in a 1:1 ratio reduced wear loss by over 10% compared to fresh oil. Social implications Reusing used engine oils can reduce their environmental impact and bring economic benefits. Originality/value This study showed that the properties of UEO can be enhanced using the solvent extraction-adsorption method. Furthermore, the study provided valuable insights into the metal concentrations in engine oil samples and their impact on lubrication performance. The order of the number of the grooves quantity and the possibility of the observed scuffing region trend relative to the samples was UEO &gt; 5W-30 fresh oil &gt; Treated oil sample with the adsorbent cement and celite together. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2024-0209/

Harnessing nano-synergy: A comprehensive study of thermophysical characteristics of silver, beryllium oxide, and silicon carbide in hybrid nanofluid formulations

Nanofluids, promising to improve heat transfer efficiency, encounter stability and durability challenges, hindering their industrial applications. The emerging concept of hybrid nanofluids, alongside surfactant-driven stability research, presents a promising solution to tackle challenges in heat transfer, potentially revolutionizing thermal management systems and advancing nanomaterial science. This comprehensive study investigates the thermophysical properties of simple and hybrid nanofluid formulations composed of silver (Ag), beryllium oxide (BeO), and silicon carbide (SiC) nanoparticles dispersed in water. Hybrid nanofluids were prepared with varying volumetric ratios of 20:80, 40:60, 60:40, and 80:20 and examined across temperatures ranging from 15 to 45 °C. The influence of surfactants on stability was explored to augment thermal characteristics. Results revealed that the surfactants have a significant effect on stability and the specific mixing ratios can lead to more favourable thermal characteristics. Thermal conductivity enhancements, evaluated via the transient hot-wire method, demonstrated improvements of 7.43 %, 7.17 %, and 5.31 % for Ag/SiC (60:40), Ag/BeO (60:40), and SiC/BeO (80:20) hybrid nanofluids, respectively, compared to water. Viscosity measurements revealed Newtonian behaviour for the Ag, SiC, and BeO nanofluids, with a minimum viscosity enhancement of 3.01 % observed for the BeO nanofluid. Hybrid Ag/SiC nanofluid demonstrated a maximum viscosity enhancement of 4.90 % for 20:80 formulation. Density analysis showed maximum augmentation of 0.25 %, 0.097 %, and 0.0775 % for the Ag, SiC, and BeO nanofluids respectively at 0.025 vol% while hybrid Ag/SiC nanofluid exhibited a maximum of 0.23 % density increase for the 80:20 composition. The statistical models were also developed to predict properties against temperature. Furthermore, the cost analysis identified Ag nanofluid as the most expensive option, while the SiC/BeO hybrid was the most economical. However, the Ag-SiC (60:40) hybrid nanofluid offered a balanced trade-off between properties and cost.

Synthesis, comprehensive characterization and investigation of biological properties of newly synthesized Pt(II)-aminothiazole complexes: Combining experimental and computational approach

The synthesis of new platinum(II) complexes with 2-amino-6-methyl-benzothiazole and 2-amino-6-chlorobenzothiazole as ligands were reported and the proposed structure of the complexes were determined using elemental microanalysis, infrared, 1H and 13C NMR spectroscopy. To verify the suggested structures a computational approach utilizing Density Functional Theory was implemented. The results showed a strong correlation with experimental data, confirming the hypothesized structures of investigated compounds.The interactions of novel platinum(II) complexes with human serum albumin and calf thymus DNA were studied by fluorescence spectroscopy and UV-Vis absorption. The predominantly elevated values of the binding constant, Kb, and the Stern-Volmer quenching constant, KSV, stem from the effective attachment of complexes to both HSA and CT-DNA. To establish the mode of interaction, viscosity measurements were conducted. The results showed that complexes are not performing intercalation between the DNA bases, and which probably bind to minor/major grooves.In vitro cytotoxic effect of ligands and platinum(II) complexes was evaluated in the panel of cancer cell lines (mouse mammary carcinoma and colon cancer, and on human mammary carcinoma and colon cancer), and on non-tumor cells, mouse mesenchymal stem cell line using MTT assay. Platinum(II) complex with 2-amino-6-methyl-benzothiazole showed a very good cytotoxic activity mainly by inducing apoptosis.In vitro antimicrobial assay of ligands and complexes was tested against 11 microorganisms using microdilution method and the minimum inhibitory concentration and minimum microbicidal concentration were identified. All tested compounds exhibited moderate antifungal activity and significantly better action on S. aureus ATCC 25923.

Experimental evaluation of green nanofluids in heat exchanger made oF PDMS

Conventional methods for synthesizing metallic nanoparticles face challenges such as instability and environmental concerns. Therefore, new, simpler, and more eco-friendly methods are being explored. In this context, the study reports a green synthesis process to produce magnetic iron oxide nanoparticles using an aqueous extract of the alga Chlorella vulgaris. This process leverages natural resources to create a sustainable nanofluid known as green nanofluid. To evaluate the characteristics of this nanofluid, experimental measurements of wettability, viscosity, thermal conductivity, and qualitative stability analysis were conducted. An experimental setup consisting of a heat exchanger made of polydimethylsiloxane (PDMS) was used to assess the thermal performance and the results were compared to theoretical equations and numerical simulation. Additionally, thermographic imaging of temperature gradients as the fluids passed over the heated surface of the serpentine channel were made. The main findings confirmed that the nanofluid was more stable than that obtained by traditional methods and had a more uniform temperature distribution over the heat exchanger. The higher concentration exhibited superior thermal performance compared to DI-Water. Moreover, the green nanofluid was used at a weight concentration of 0.1 wt%, provided thermal performance results of nearly 4.5% superior to those estimated by the numerical model and 6.4% higher than those experimentally obtained with the base fluid, respectively. Finally, the results obtained for the nanofluid also showed an average increase of around 5% in the viscosity of the base fluid, with a more significant sedimentation at a concentration of 0.1 wt%.

Engineering Water-shut-off Operations: Application of Rheological Time-Temperature Superposition Approach for Organically-Crosslinked Polymer Gel Systems

Polymer-based gels have been extensively utilized in reservoirs to prevent excessive water production and improve oil recovery. In this study, a sulfonated-hydrolyzed polyacrylamide polymer (HPAM-S) and low-toxic organic crosslinkers (hydroquinone and hexamethylenetetramine) were mixed in brine at specified concentrations to formulate the polymer-crosslinker fluid system. The quantitative rheological analysis, along with the TTS (Time-Temperature Superposition) approach, was examined for the first time to achieve the water shut-off operations in high-temperature reservoirs (90°C to 150°C). The TTS approach was defined as modelling of the viscosity vs. time data obtained at various temperatures using an appropriate empirical shift factor ) such that a single master curve is established for the viscosity evolution of the given fluid system. This approach facilitates the prediction of the gelation behavior of polymer-crosslinker fluid systems as a function of time at varied reservoir temperatures especially over time scales that are not experimentally accessible. The time-dependent rheological evolution of the fluid system was experimentally investigated using batch-wise bottle testing methods as well as viscosity and viscoelastic measurements by employing an advanced rheometer. The TTS approach was applied to the obtained rheological data at varied temperatures. The model was validated for an unknown set of temperature vs. viscosity data. Based on the TTS approach, the term ‘gelation time’ was defined as the time required to reach a pre-specified viscosity to signify a transition from the liquid-like state to the solid-like state. The gelation time decreases with increasing temperatures. After the gelation time, at each temperature, a swift increase in the fluid viscosity was observed, indicating the initiation of the rapid crosslinking in the fluid systems. It was found that beyond the gelation time, the batch-wise bottle testing showed (G-I) gel strength (qualitative). Analogously, the visco-elasticity test demonstrated a rapid rise in elastic modulus (G’) beyond the gelation time. An underlying mechanism based on polymer hydrolysis was utilized to explain the evolution of distinct viscous and viscoelastic properties as a function of temperature. Moreover, the modeling predictions for the fluid systems were examined for in-situ rock plugging with the help of core-flood equipment. The core-flooding tests confirmed a 99% reduction in the rock permeability beyond the gelation time. The gelation time values obtained from both the batch-wise bottle testing method and rheological tests for the polymer-crosslinker fluid systems were found in agreement with each other, with a tolerance of (±5%).