Light Liquids Research Articles

Effect of different polishing methods applied to denture base materials on microbial adhesion and surface roughness

Aim: The aim of our study was to investigate the effect of various polishing processes applied to different types of PMMA (polymethyl methacrylate) denture base materials on the surface roughness and microbial adhesion of the base material. Methods: Sixty specimens each were prepared from heat-polymerized conventional PMMA (G), heat-polymerized injectable PMMA (E), and prepolymerized CAD/CAM PMMA (C) denture base materials. All sample surfaces were sanded with 800, 1000, 1200, and 2500 grit silicone carbide abrasives. The specimens of each denture base material were divided into three subgroups (n=20) in which different polishing methods were applied. The first group was mechanically polished (M), and the other two groups were chemically polished with light polymerized glaze liquids [Palaseal (Ps), Optiglaze Color (Og)]. A profilometer device was used to evaluate the surface roughness. Colony counting was performed to evaluate bacterial colonization after one day. The data obtained from all these measurements were evaluated using an analysis of variance, and Bonferroni corrected test was used for multiple comparisons of means (p=0.05). The interaction between surface roughness and bacterial colonization was examined by the Pearson correlation test. Regression analysis was performed to determine the relationship between them. Results: When PMMA base materials were compared, the lowest average surface roughness (Ra) values and bacterial colonization values were obtained in Group C. When polishing methods were compared, the lowest average surface roughness values were obtained in Group M. As a result of bacterial colonization measurement, lower colonization values were obtained with standardized mechanical polishing compared to other groups. Conclusion: There was no difference between the different PMMA base materials in terms of surface roughness, but there were statistical differences in bacterial colonization. The results of our study showed that mechanical polishing gave better results than light-activated glazing agents. How to cite this article: Yarar S, Değer Y, Tekin S. Effect of different polishing methods applied to denture base materials on microbial adhesion and surface roughness. J Med Dent Invest 2023; 4: e230351. https://doi.org/10.5577/jomdi.e230351

Separation and direct-indirect analysis of six group components from liquids of kerosene co-refining

The composition and structure of kerosene co-refining products (KCR) need to be studied to promote their further processing and utilization besides for making fuels. In this paper, their composition and structure were analyzed layer by layer from top to bottom in the form of “Surface (KCR)-Line (six group components, SGCs)-Point (compounds)”. SGCs combine extraction and column chromatography to provide a method for highly efficient separation of heavy hydrocarbons. Insoluble components (asphaltene, ASP) and n-heptane soluble (HS) were obtained from light and heavy liquids (LP and HP) of KCR by Soxhlet extraction. HS was gradient eluted by chromatographic column with different solvents and α-Al2O3, and separated into other five group components: saturates (SA), aromatics (AR), heteroatoms (HE), phenolics (PH) and resins (RE), wherein the results show that the extraction yields of LP-SA, LP-AR, LP-PH, LP-RE are 68.53 wt%, 7.28 wt%, 3.55 wt% and 1.20 wt%, and the extraction yields of HP-SA, HP-AR, HP-HE, HP-PH, HP-RE are 36.06 wt%, 25.13 wt%, 6.27 wt%, 4.53 wt% and 2.37 wt%, respectively. Physical and chemical characterization of the raw materials and SGCs were analyzed by TG, FTIR, 13C NMR, GC/MS, and Py-GC/MS, in which the combination of GC/MS and Py-GC/MS can fully detect the light and heavy components in LP and HP, including those difficult to detect above 300 °C. The final thermal mass loss rates of these components follow the order of LP-SA > LP-AR > LP-PH > LP-RE and HP-SA > HP-AR > HP-PH > HP-HE > ASP > HP-RE. The aromatic carbon mass ratio (fa) of LP and HP is 15.27% and 19.45%, respectively. n-Alkanes (C11–32) are the main compounds in LP and HP, followed by polycyclic aromatics with 3–4 R. Aromatics are rich in -CH2- bridge bond to generate light aliphatics and aromatics at 500 °C, especially the ASP generates many monocyclic aromatics with the increase of temperature by Py-GC/MS. In addition to aliphatics and aromatics, alkyl phenols, esters, pyridines and thiophenes are the main compounds in LP and HP.

A New Method for Determining Interfacial Tension: Verification and Validation

Surface tension is a meaningful parameter influencing boiling and condensation in macroscopic scale, in confined spaces, or for nanofluids; it further affects boiling with surfactants. Surface, or interfacial, tension is an important property in the research into increasing heat transfer, enhancing efficiency of photovoltaic systems, improving engine operation, or forming drugs or polymers. It is often determined using axisymmetric drop shape analysis based on the differential equations system formulated by Bashforth and Adams. The closed-form expression of the interface shape states the radii defining the bubbles are the negative numbers, which causes the temperature profile drops along the heat transfer direction, e.g., in the Wiśniewski formulas for the temperature in the vapor bubbles; moreover, the drop, or bubble, possesses only one main radius of curvature, which may reduce the number of the unknowns and equations in the Bashforth and Adams algorithm. An alternative method applying the closed-form expression for the droplet shape is validated for the water (denser) drop flowing down in octane (the lighter liquid); its spare equation is used for verifying the outcomes.

Thiophene-functional hierarchical carbons for the removal of ionic and organic mercury in light hydrocarbon liquids: Synthesis, evaluation and adsorption mechanism

A simple synthesis of thiophene-functional zeolite-templated carbons (ZTCs) is proposed to remove ionic mercury (Hg2+) and organic mercury (Hgorg) from gasoline. Microporous zeolite (Beta) and mesoporous zeolite (MCM-41) were used to prepare porous carbon by impregnating with 2-thiophenemethanol (ThM) to explore the influence of template type on the quality of templated carbon. The amount of strong acidic sites in MCM-41 zeolite was more than Beta zeolite which promoted the catalytic polymerisation of the ThM in the pores structure of the zeolite and highly templated carbon was obtained. The impregnation concentration of ThM on the structure and functional groups of the samples was explored. It was found that increasing the concentration of ThM properly can promote the filling of zeolite pores by ThM and form more ordered templated carbons. In addition, the increased ThM promoted the formation of the S = O and C-O oxygen-containing functional groups. The optimal impregnation concentrations of ThM were 25% for B-Al (25%-B-Al-ZTC) and 75% for M−Al (75%-M−Al−ZTC). The 75%-M−Al−ZTC with sufficient S = O and C-O oxygen-containing functional groups showed excellent mercury adsorption capacity (617.49 μg/g) and a high intra-particle diffusion rate (294.10 h−1). The simultaneous adsorption of Hg2+ and Hgorg was also conducted and it was found that Hgorg had competitive adsorption for Hg2+ which led the total adsorption capacity to decrease. In addition, the 25%-B-Al-ZTC and 75%-M−Al−ZTC adsorbents had good regeneration ability and the adsorption capacity remained over 75% and 71% for Hg2+ and Hgorg after five desorption-sorption cycles, respectively. Thus, the new adsorbents with stable and efficient Hg removal performance have the potential for practical application by oil refineries.

Spinodal de-wetting of light liquids on graphene

We demonstrate theoretically the possibility of spinodal de-wetting in heterostructures made of light–atom liquids (hydrogen, helium, and nitrogen) deposited on suspended graphene. Extending our theory of film growth on two-dimensional (2D) materials to include analysis of surface instabilities via the hydrodynamic Cahn–Hilliard-type equation, we characterize in detail the spatial and temporal scales of the resulting spinodal de-wetting patterns. Both linear stability analysis and direct numerical simulations of the surface hydrodynamics show micron-sized (generally material dependent) patterns of ‘dry’ regions. The physical reason for the development of such instabilities on graphene can be traced back to the inherently weak van der Waals interactions between atomically thin materials and atoms in the liquid. Thus 2D materials could represent a new theoretical and technological platform for studies of spinodal de-wetting.

Removing ionic and organic mercury from light hydrocarbon liquids by ordered zeolite-templated carbon doped with sulphur

Sulphur-doped, β-zeolite-templated carbons (S-β-ZTCs) were synthesized by chemical vapor co-deposition of hydrogen sulfide (H2S) and acetylene (C2H2) to remove ionic (Hg2+) and organic mercury (Hgorg) from gasoline. In situ doping of sulphur introduced aromatic thiols and thiophenes into the ZTC's framework that removed the mercury by forming Hg–S bonds. Notably, these covalently bonded sulphur groups exhibited better stability than physically deposited elemental sulphur, yielding less than 10% material loss after repeated adsorption-desorption tests. Thanks to these unique chemical properties, the adsorption capacity of S-β-ZTCs for Hg2+ in the gasoline (2660 μg/g) was at least an order of magnitude larger than that of common adsorbents. Moreover, simultaneous adsorption of Hg2+ and Hgorg on S-β-ZTCs proceeded independently when the total mercury concentration was in the range applicable to most natural gas condensate samples. Finally, Grand Canonical Monte Carlo (GCMC) method and Density Functional Theory (DFT) study were used to reveal the adsorption mechanism of ZTCs on Hg2+ and Hgorg. These findings provided a better understanding of the mercury sorption mechanism of S-β-ZTCs and have important practical significance for the clean production of the condensate processing industry.

Deformation characteristics of the bubble in water-biodiesel immiscible fluids

It is of great significance to investigate the rising behavior of a bubble in immiscible fluids in chemical and metallurgical engineering. A 3-D model is established and the free-floating behavior of a single bubble in immiscible fluids (water-heavier liquid and biodiesel-lighter liquid) is numerically simulated by phase-field method. After the fluctuation of a certain distance, the bubble tends to be stable. It takes more time for the larger bubble to reach a stable shape than for the smaller one. The terminal aspect ratio of bubble, ET, with the same size in heavier liquid is smaller than that in lighter liquid. With the increase of bubble size, ET becomes small both in heavier and lighter liquid. Comparing bubble vortex diagrams of different shapes shows that the maximum vortex intensity is the direction in which the bubble shape extends. When the bubble passes through the liquid-liquid interface, it will form ?pear?, ?inverted pear?, ?convex?, and ?water drop? shapes successively.

Raman scattering of plane-wave and twisted light off chiral molecular liquids

We present an experimental study of the quasi-elastic Raman scattering (QES) of plane-wave and twisted light by liquid crystals. Depending on their temperature, these crystals can exhibit isotropic, nematic and chiral nematic phases. The question is addressed of how the phase of a crystal and the state of incident light can affect the quasi–elastic energy spectra of the scattered radiation, whose shape is usually described by the combination of Lorentzian and Gaussian components. Special attention is paid to the chiral phase, for which the Raman QES spectrum is dominated by a Lorentzian with reduced linewidth, pointing to diminished disorder and configurational entropy. Moreover, this phase is also known for a regime of iridescence (selective backscattering) which arises when the wavelength of incident light becomes comparable with the chiral pitch length. Detailed measurements, performed in this resonant regime and by employing twisted light, carrying various projections of the orbital angular momentum (OAM), have indicated a low-energy scattering surplus depending on OAM. We argue that this observation might indicate a transfer of angular momentum between light and liquid crystal.

Kerogen Swelling in Light Hydrocarbon Gases and Liquids and Validity of Schroeder’s Paradox

Kerogen is often the organic part of the shale and provides the pore space for a large part of the hydrocarbons in place. Kerogen molecules are flexible like polymer molecules, and may swell when i...

Time-resolved PIV measurements of a deflected submerged jet interacting with liquid-gas and liquid-liquid interfaces

This paper presents an experimental investigation on the interactions of a deflected submerged jet into a liquid pool with its above interface in the absence and presence of an additional lighter liquid. Whereas the former is a free surface flow, the latter mimics a situation of two stratified liquids where the liquid-liquid interface is disturbed by large-scale motions in the liquid pool. Such configurations are encountered in various industrial applications and, in most cases, it is of major interest to avoid the entrainment of droplets from the lighter liquid into the main flow. Therefore, it is important to understand the fluid dynamics in such configurations and to analyze the differences between the cases with and without the additional liquid layer. To study this problem, we applied time-resolved particle image velocimetry experiments with high spatial resolution. A detailed data analysis of a small layer beneath the interface shows that although the presence of an additional liquid layer stabilizes the oscillations of the submerged jet significantly, the amount of kinetic energy, enstrophy, and velocity fluctuations concentrated in the proximity of the interface is higher when the oil layer is present. In addition, we analyze the energy distribution across the eigenmodes of a proper orthogonal distribution and the distribution of strain and vortex dominated regions. As the main objective of this study, these high-resolution time-resolved experimental data provide a validation platform for the development of new models in the context of the volume of fluid-based large eddy simulation of turbulent two-phase flows.

Quantifying the benefits of in-time and in-place responses to remediate acute LNAPL release incidents

Acute large volume spills from storage tanks of petroleum hydrocarbons as light non aqueous phase liquids (LNAPLs) can contaminate soil and groundwater and may have the potential to pose explosive and other risks. In consideration of an acute LNAPL release scenario, we explore the value of a rapid remediation response, and the value of installing remediation infrastructure in close proximity to the spill location, in effecting greater recovery of LNAPL mass from the subsurface. For the first time, a verified three-dimensional multi-phase numerical framework and supercomputing resources was applied to explore the significance of in-time and in-place remediation actions. A sand aquifer, two release volumes and a low viscosity LNAPL were considered in key scenarios. The time of commencement of LNAPL remediation activities and the location of recovery wells were assessed requiring asymmetric computational considerations. The volume of LNAPL released considerably affected the depth of LNAPL penetration below the groundwater table, the radius of the plume over time and the recoverable LNAPL mass. The remediation efficiency was almost linearly correlated with the commencement time, but was a non-linear function of the distance of an extraction well from the spill release point. The ratio of the recovered LNAPL in a well located at the centre of the spill/release compared to a well located 5 m away was more than 3.5, for recovery starting only 7 days after the release. Early commencement of remediation with a recovery well located at the centre of the plume was estimated to recover 190 times more LNAPL mass than a one-month delayed commencement through a well 15 m away from the centre of the LNAPL plume. Optimally, nearly 40% of the initially released LNAPL could be recovered within two months of commencing LNAPL recovery actions.

Preparation of TiO2 bionic surperhydrophobic surface on AZ31 and it’s anti-corrosion properties

Superhydrophobic surface containing TiO2 was prepared on the surface of AZ31 magnesium alloy by two-step method. The morphology and composition of the film were characterized by SEM, XRD and FT-IR. The physical and chemical stability of the film was investigated by friction and wear test and contact angle test under different conditions. In addition, self-cleaning performance and corrosion resistance of the film were studied. The results showed that the superhydrophobic surfaces have good resistance to ultraviolet light, acidic and alkaline liquids, which prove that good mechanical stability and chemical stability.

Pattern Formation in Glass Caused by Rayleigh-Taylor Instability

Beautiful patterns such as snowflakes, wind ripples, and cloud patterns are ubiquitous in nature. Some of those are formed by interfacial instability. We focus on two pattern formations caused by the Rayleigh-Taylor instability. Rayleigh-Taylor instability is an interfacial instability between two liquids that occurs when a heavier liquid is on a lighter liquid. The first pattern we discuss is a fractal/cell pattern in a coffee cup. If a droplet of coffee solution is placed on milk, the coffee solution spreads on the surface of the milk. Then the Rayleigh-Taylor instability occurs at the interface between the coffee solution and milk, and the coffee solution starts to sink into the milk. We found that the fractal or the cell pattern is formed at the surface of the milk in this process. We showed that an aspect ratio between the radius of the container and the depth of the milk affects vertical flow and it leads to a transition between the fractal pattern and the cell pattern. We also showed that the fractal pattern is formed by a similar mechanism of a viscous fingering. The second pattern is a breakup of a droplet. A sinking droplet in a viscous solution spontaneously deforms to a vortex ring and then breaks up spontaneously. We experimentally investigated relations among breakup number, radii of droplets, viscosities and density differences between two solutions. We also proposed a phenomenological model considering the Rayleigh-Taylor instability. The phenomenological model provides a non-dimensional parameter derived from a radius of a droplet, viscosity and a density difference between two liquids. And, the model states that the breakup number is classified by the parameter. Our experimental results obey the parameter. It means that the competition between a driving force of gravity and the viscosity dissipation at the interface of two solutions determines the breakup number.

Innovative device to assay leachate production in non-sanitary landfills

Improper landfills (waste dumps) are common waste disposal systems in developing countries and represent sources of environmental pollution. These sites defy researchers and managers because they lack structures to collect liquid, solid and gaseous samples, which make it challenging to monitor local environmental quality. In this work, we show one device for sample collection to monitor leachate quality in a closed waste dump in Brazil. During the installation of this device (Leachate Monitoring Station, LMS), interesting facts about the structural, physical, and chemical composition of an old dump could be visualized. Two different kinds of leachate were found: the accumulated leachate (AL), a thick dark fluid entrapped above non-degraded material, and the mobile leachate (ML), a lighter liquid which flowed into the LMS, and thus was not stagnant like AL. In the AL, the chemical oxygen demand and total ammoniacal nitrogen average concentrations were about 21,500 mg/L and 1000 mg/L, respectively, which were considerably higher than the ML concentrations, of about 1100 mg/L and 200 mg/L, respectively, for the same parameters. Thus, despite the lower concentrations of hazardous substances in the ML, the waste body stores pockets of leachate (AL) with significant concentrations of hazardous compounds, even after 15 years of the dumpsite closure. Moreover, waste solubilization assays showed that the solid material could not be considered inert according to the Brazilian Standard Norm NBR 10004/2004. The installation of the LMS enabled a new understanding about pollutant accumulation inside waste deposits and provided an effective, low-cost tool to monitor leachate production in non-sanitary landfills. The results warn about the risks that old dumpsites still pose to the environment and reinforce the need for a post-care action plan for managing uncontrolled waste deposits.

Cavitation bubble collapse in a vicinity of a liquid-liquid interface – Basic research into emulsification process

The initial motivation for the study was to gain deeper understanding into the background of emulsion preparation by ultrasound (cavitation). In our previous work (Perdih et al., 2019) we observed rich phenomena occurring near the liquid-liquid interface which was exposed to ultrasonic cavitation. Although numerous studies of bubble dynamics in different environments (presence of free surface, solid body, shear flow and even variable gravity field) exist, one can find almost no reports on the interaction of a bubble with a liquid-liquid interface. In the present work we conducted a number of experiments where single cavitation bubble dynamics was observed on each side of the oil-water interface. These were accompanied by corresponding simulations. We investigated the details of bubble interface interaction (deformation, penetration). As predicted, by the anisotropy parameter the bubble always jets toward the interface if it grows in the lighter liquid and correspondingly away from the interface if it is initiated inside the denser liquid. We extended the analysis to the relationships of various bubble characteristics and the anisotropy parameter.Finally, based on the present and our previous study (Perdih et al., 2019), we offer new insights into the physics of ultrasonic emulsification process.

Investigation of Ni─Ca binary catalystic activities for production of light aromatics from catalytic pyrolysis of brown coal

AbstractThe pyrolysis behavior of Ni─Ca‐loaded Yunnan brown coals (Shi Caoxing [SCX] and Guo Jiashan [GJS]) was studied in a fixed‐bed reactor to investigate the effects of Ni, Ca, and Ni─Ca loading on the yields of the obtained liquids and light aromatic hydrocarbons. Structural variations of the prepared coal chars were characterized by the scanning electron microscope–energy dispersion X‐ray, Fourier‐transform infrared spectroscopy, X‐ray diffractometer, Brunauer–Emmett–Teller analysis, and elemental analysis. The effects of the Ni, Ca, and Ni─Ca loadings on the tar yield and upgradation of pyrolysis tar were evaluated. The results revealed that the use of the Ni─Ca catalyst affords improved yields of the liquid products and tar. Furthermore, the light hydrocarbon liquids contents in the coal tar was improved with the use of the Ni─Ca catalyst. The heavy components and polycyclic aromatic hydrocarbons in the coal tar could be easy to convert into light hydrocarbon liquids (phenol, cresol, xylenols, and naphthalene) with the SCX brown coal pyrolysis. In contrast, the catalytic pyrolysis of GJS brown coal was inhibited by the Ni─Ca catalyst. The study revealed that the catalytic activity of the Ni─Ca catalyst greatly depends on the type of the coal substrate and was promoted or inhibited depending on the type of the brown coal.

Liquid Penetration Depth and Strength of Concretes Modified with Polymer Admixtures Under the Action of Crude-Oil Products

In the present article, the research results of concretes modified with a polymer dispersion of vinyl-benzene and acrylic (PC1) and with a styrene–butadiene dispersion (PC2) are discussed. Concretes were exposed to diesel, non-ethylated fuel, and the standard mixture of light liquids for 1000 h. Concretes modified with polymer dispersions, especially with the styrene–butadiene dispersion (PC2), indicated a smaller degree of liquid penetration into the depth of samples compared to the control concrete. The compressive strength for tested concretes, determined after 1000 h of storage in crude-oil products, in comparison to the strength of samples stored in de-mineralized water was significantly decreased, with the maximum differences equal to 12% for PC2 concrete.

Simulation on mass transfer at immiscible liquid interface entrained by single bubble using particle method

As a Lagrangian particle method, Moving Particle Semi-implicit (MPS) method has great capability to capture interface/surface. In recent years, the multiphase flow simulation using MPS method has become one of the important directions of its developments. In this study, some key methods for multiphase flow have been introduced. The interface tension model in multiphase flow is modified to maintain the smooth of the interface and suitable for the three-phase flow. The mass transfer at immiscible liquid interface entrained by single bubble which could occur in Molten Core-Concrete Interaction (MCCI) has been investigated using this particle method. With the increase of bubble size, the height of entrainment column also increases, but the time of film rupture is slightly different. With the increase of density ratio between the two liquids, the height of entrained column decreases significantly due to the decreasing buoyancy of the denser liquid in the lighter liquid. In addition, the larger the interface tension coefficient is, the more rapidly the entrained denser liquid falls. This study validates that the MPS method has shown great performance for multiphase flow simulation. Besides, the influence of physical parameters on the mass transfer at immiscible interface has also been investigated in this study.

4-Lump kinetic model of the co-pyrolysis of LDPE and a heavy petroleum fraction

Pyrolysis of post-consumer plastics is a promising strategy to recover valuable hydrocarbons from waste streams. In this study, the lumping approach is adopted to model the kinetics of a continuous co-pyrolysis process for low-density polyethylene (LDPE) and a heavy petroleum residue fraction (HPR). All evolving species are merged in four lumps based on their boiling range: residue (R, >410 °C), spindle oil (SO, 350–410 °C), light liquids (LL, IBP – 350 °C) and gas (G, noncondensable at 0 °C). The experimental results of a tubular laboratory cracker with a mixture of LDPE and HPR at different reactor lengths between 19.4 and 33 m provide data to estimate kinetic parameters for all six considered reactions and the overall reaction enthalpy. Based on the rate equations for irreversible, monomolecular, first-order reactions and the mass and heat balance of an incrementally modeled tubular reactor, a MATLAB algorithm solves the optimization problem including a bottom-up approach to find suitable initial values. The calculated frequency factors vary over a wide range from 102 to 108 s−1 and the obtained activation energies are between 147 and 313 kJ mol−1. The determined value for the overall reaction enthalpy is 4669 kJ mol−1. The results of the modeled system are in good agreement with experimental yields and can be implemented into a process model of the LDPE-HPR co-pyrolysis for simulation and optimization purposes.

Passage of a bubble through the interface between a shear-thinning heavier liquid and a Newtonian lighter liquid

Numerical simulations are carried out to study the phenomenon of passage of a bubble through the interface between two initially quiescent liquids. The heavier liquid is a viscous shear-thinning liquid whereas the lighter liquid is a viscous Newtonian liquid. The computational model, which is based on axisymmetric computational domain and VOF (volume of fluid) method, is validated by using the data reported in literature. The validated computational model is then used to perform parametric analysis to understand the effects of bubble diameter, interfacial tension between the two liquids and flow index of the heavier liquid on the drainage time, drainage height, retention time and retention height of the bubble at the liquid–liquid interface. Finally, correlations for retention time and retention height are proposed.