Glass Viscosity Research Articles

Raman study of photoinduced crystallization of SnS2 in As2S3:Sn glasses

Raman spectra of synthesised As2S3:Sn samples with up to 2.7 at% Sn recorded at a moderate excitation power density (Pexc=4 kW/cm2) show their amorphous character. Raman measurements performed at a higher Pexc (40 kW/cm2) result in the local heating of the sample surface by up to 150 K, as estimated from the shift of the frequency positions of the As2S3 Raman maxima. For samples with Sn content above 2 at% a pronounced narrow peak at 311 cm–1 emerges as an evidence for SnS2 crystallites formed on the sample surface under above-bandgap illumination during the measurement. The higher-Pexc (40 kW/cm2) illumination results in a formation of a pit on the sample surface due to the material transfer and in a rapid decrease of the glass viscosity, enhancing the diffusion of atoms and facilitating their aggregation in SnS2 crystallites. This effect of mostly nonthermal nature is responsible for the SnS2-related feature observed in the Raman spectra upon illumination at Pexc= 40 kW/cm2. For As2S3 doped with 3 at% Sn the SnS2-related feature near 314 cm–1 is observed in the Raman spectra even under excitation at much lower Pexc, down to 0.4 kW/cm2. As follows from X-ray diffraction data, no crystalline SnS2 phase is present in this sample before the measurement, it appears upon illumination even at the low Pexc values.

Analysis of pore morphology evolution of all-wastes ceramic foams based on the variation of composition and sintering process

Utilization of wastes for the preparation of ceramic foams has gradually become a major direction in the development of new building materials. In this paper, all wastes-based ceramic foams based on electrical insulators waste (EIW) and red mud (RM) were prepared through the high-temperature foaming method. The factors affecting the increase in pore size under different preparation conditions (RM content, temperature and time) were investigated separately by studying the changes in pore size. With the increase of RM content, sintering temperature and sintering time, the pore morphology gradually evolved from a regular spherical shape to a polygonal or irregular shape with a corresponding increase in pore size, albeit at different rates. The pore size enhancement ascribed to changes in RM content was primarily attributed to the synergistic influences of a plurality of factors including glass phase content, viscosity, and gas phase content. Sintering temperature mainly affected the balance between the forces acting inside and outside the pores and the gas phase solubility in the liquid phase to adjust the size of pores. The influence of sintering time on pore size and morphology emanated from the glass phase viscosity and the resulting changes in the release rate of gas phase. In summary, the study will help to investigate the actual controlling factors of composition and process on the pore structure, and provides significant insights into the optimization and adjustment of pore structure for samples obtained by high-temperature sintering.

Kinetic and thermodynamic property study of electrostatic-assisted porous liquids, nanofluids and nanoparticle organic hybrid materials by molecular dynamics simulation

Despite similar components, electrostatic–assisted porous liquids, nanofluids and nanoparticle organic hybrid materials have different stability, thermodynamic and kinetic characteristics, mainly because of different preparation methods and core contents. In this work, porous liquids proved to be fluid at near room temperature and exist stably by molecular dynamics simulations. In contrast, nanoparticles of nanofluids tended to aggregate from one another because of the strong interaction between nanoparticles when the canopies were squeezed out. In addition, simulation results demonstrated that the degree of polymerization, core size and grafting density had distinct effects on glass transition temperature, dispersion and viscosity, which were brought by a combination of factors, including solid content and intramolecular / intermolecular entanglement.

Viscosity, Glass Formation, and Mixing Times within Secondary Organic Aerosol from Biomass Burning Phenolics

Biomass burning events emit large amounts of phenolic compounds, which are oxidized in the atmosphere and form secondary organic aerosol (SOA). Using the poke-flow technique, we measured relative humidity (RH)-dependent viscosities of SOA generated by the oxidation of three biomass burning phenolic compounds: catechol, guaiacol, and syringol. All systems had viscosity < 3 × 103 Pa s at RH ≳ 40% and > 2 × 108 Pa s at RH ≲ 3% at room temperature. At RH values of 0–10%, the viscosities of these SOA were at least 2 orders of magnitude higher than the viscosity of primary organic aerosol from biomass burning. We also developed a parameterization for predicting the viscosity of phenolic biomass burning SOA as a function of RH and temperature. Based on this parameterization, the viscosity of phenolic biomass burning SOA is strongly dependent on both RH and temperature. Under dry conditions, phenolic biomass burning SOA is highly viscous at room temperature (∼109 Pa s) and becomes a glass (viscosity > 1012 Pa s) when the temperature is < 280 K. For tropospheric temperature and RH values, phenolic biomass burning SOA is often in a liquid state (η < 102 Pa s) below ∼2 km altitude, a semi-solid state (102 < η < 1012 Pa s) between ∼2 and ∼9 km, and a glassy state (η > 1012 Pa s) above ∼9 km. Furthermore, the mixing time of organic molecules in a 200 nm phenolic biomass burning SOA particle exceeds 1 h above 3 km in the troposphere.

Process parameter optimisation for manufacturing porous bioactive silicate glass microspheres via flame spheroidisation: The goldilocks effect

This study investigated the influence of flame spheroidisation process parameters for successfully manufacturing solid (dense) and highly porous microspheres from Food and Drug Administration approved bioactive 45S5 glass and 45S5 with addition of viscosity modifiers (i.e. 2 and 5 mol% borax and V2O5), compared against successfully processed phosphate glass microspheres (termed P40). Characterisation studies performed included thermal analysis (SDT), glass viscosity measurements using high temperature rotational viscometry and hot stage microscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis.This study revealed that aside from intrinsic material properties (i.e. melt temperature and viscosity profiles), process parameters including starting glass particle size, cooling rate and gas flow rates were important factors in achieving the desired porous glass microsphere morphology. Considering the above influential factors, a processing model has been proposed for the manufacture of highly porous microspheres from bioactive silicate glasses.

Remarkable relation between melting entropy and kinetic viscosity in metallic glasses

There has been so far no consensus regarding the roles of melting entropy on glass formation. For this purpose, a study has been conducted on three compositions of the pseudo-binary alloys, Zr2Ni-Ti2Ni, viz., the eutectic compositions (Zr2Ni)0.206(Ti2Ni)0.794, (Zr2Ni)0.654(Ti2Ni)0.346, and the Laves compound (Zr2Ni)0.44(Ti2Ni)0.56. The study results of melting entropies, melting viscosities, and glass formabilities of the alloys unequivocally shows the fact that low melting entropy and high melting viscosity facilitate glass formation. From the data of different classes of systems, a unique relationship between melting entropy and melting viscosity has arisen in glass forming systems, which highlights the positive roles of low melting entropy on glass formation from a special perspective. This study of thermodynamics, kinetics, and glass formation highly suggests the melting entropy should be taken as a crucial reference for designing metallic glasses.

Volume nanogratings inscribed by ultrafast IR laser in alumino-borosilicate glasses.

Self-assembled nanogratings, inscribed by femtosecond laser writing in volume, are demonstrated in multicomponent alkali and alkaline earth containing alumino-borosilicate glasses. The laser beam pulse duration, pulse energy, and polarization, were varied to probe the nanogratings existence as a function of laser parameters. Moreover, laser-polarization dependent form birefringence, characteristic of nanogratings, was monitored through retardance measurements using polarized light microscopy. Glass composition was found to drastically impact the formation of nanogratings. For a sodium alumino-borosilicate glass, a maximum retardance of 168 nm (at 800 fs and 1000 nJ) could be measured. The effect of composition is discussed based on SiO2 content, B2O3/Al2O3 ratio, and the Type II processing window is found to decrease as both (Na2O + CaO)/Al2O3 and B2O3/Al2O3 ratios increase. Finally, an interpretation in the ability to form nanogratings from a glass viscosity viewpoint, and its dependency with respect to the temperature, is demonstrated. This work is brought into comparison with previously published data on commercial glasses, which further indicates the strong link between nanogratings formation, glass chemistry, and viscosity.

Application of Mössbauer spectroscopy and FT-IR to describe coordination of amphoteric ions in structure of glasses from the SiO2–Na2O–MgO–CaO–Al2O3–Fe2O3 system

Glasses from the SiO2-Na2O-MgO-CaO-Al2O3-Fe2O3 system include, among others, amorphous materials obtained by the vitrification of industrial slags, ashes, dusts, but also various hazardous wastes (e.g. asbestos) containing a high proportion of Al2O3 and Fe2O3 oxides in their basic composition. The main goal of the work was to evaluate the method of incorporation into the glass structure of amphoteric ions (Fe2+, Fe3+ and Al3+) incorporation into the glass structure and its effect on the glass viscosity. A mixture of 10 wt% and 12 wt% pure Fe2O3 powder and float glass cullet was melted in an electric furnace at 1450°C for 4 hours and then poured onto a steel plate. X-ray results confirmed the amorphous structure of all molten glasses. The viscosity of glasses was examined using linear dilatometry and high-temperature microscopy. Fourier transform infrared (FT-IR) and Mössbauer spectroscopy were used to study the coordination number of amphoteric ions and how they were incorporated into the glass lattice. The research confirmed that the increase in the share of amphoteric metal ions in the coordination number 4 causes the incorporation of these ions into the glass network. Metal ions Fe2+, Fe3+ and Al3+ occurring in tetrahedral coordination, depositing in the glass network next to Si4+ ions, strengthen the network and, as a result, can increase its viscosity in the range of forming temperatures.

Crystallization behavior and ionic conductivity of NASICON type glass-ceramics containing different amounts of B2O3

In this research, glass-ceramics belonging to the system of Li2O-TiO2-P2O5 were prepared by the addition of different amounts of B2O3. The glass formation ability of the starting glass materials along with the crystallization trend as well as ionic conductivity of the corresponding glass-ceramics were also examined. Starting glasses were obtained through the melt quenching technique and glass-ceramics specimens were prepared through one-step heat treatment. The glass-ceramic samples were then examined through X-ray diffractometry, differential thermal analysis, electrochemical impedance spectroscopy, and scanning electron microscopy. According to the obtained results, the addition of a 2.5 mole% of B2O3 to the glass composition led to a sharp increase in ionic conductivity at room temperature. So that the bulk conductivity of the specimen heat treated at 950 °C for 2 h was measured to be 1.17 × 10-3 Scm-1, which was 10 times bigger than that of the base glass-ceramic with no additive. It also decreased the crystallization temperature and viscosity of the parent glass, resulting in increased crystallinity while further addition of B2O3 drained the conductivity and crystallinity of glass-ceramics.

Insights on surface analysis techniques to study glass primary packaging

AbstractDuring the forming process of a vial by tubing glass, temperatures of up to 1200°C are applied to adjust the glass viscosity. This process causes the release of volatile components such as alkali borates. Consequently, the percentage of sodium and boron measured on the inner surface of the vial can be higher than that measured on the corresponding glass tube. This study aimed to characterize the inner surface of two different borosilicate glass tubes of type I before and after the vial forming process at the nanoscale level. Quantitative elemental analysis of the surface along the vertical axis of glass tubes and vials was performed by X‐ray photoelectron spectroscopy, whereas the topographical investigation was carried out by scanning electron microscopy (SEM). In the near‐bottom region of a vial, which is usually the area most prone to corrosion, the SEM micrographs showed the appearance of bulges on the surface. The latter were then analyzed by time‐of‐flight secondary ion mass spectrometry to characterize their molecular composition. The purpose of this work is to identify possible new strategies for faster identification of factors that eventually influence chemical resistance of pharmaceutical glasses and to provide useful information needed to improve industrial processes.

Assigning Viscosity Values in the Glass Softening Temperature Range

A new optical method for assigning glass viscosity values in the softening temperature range is presented. In this method, an irregular particle, a few millimeters in size, laying on an alumina plate, is heated up to temperature T, and then remains at this temperature. T should be within the softening temperature range of the glass. There are no external applied shear stresses, the only acting shear forces are those coming from the particle's own surface energy. At the fixed temperature T, the surface free energy of the sample decreases by viscous flow while its shape evolves from a polyhedron or irregular shape towards a spherical or rounded shape. This shape evolution is recorded using a photographic camera. From each image, the sample's roundness is determined, obtaining a characteristic time τ from the roundness against time. Simultaneously, using the available software, a value for the viscosity η was calculated, at temperature T, allowing for building sets of T, τ, η, namely three data values. Accordingly, if T, τ are considered as independent variables, a master function η = η (T, τ) can be built. Now, if we measure T, τ data on a glass of an unknown viscosity, the master function makes it possible to assign a η value. When incipient crystallization or liquid-liquid phase separations are present, effective viscosity values are obtained. This method requires a high temperature microscope, as well as tridimmensional samples with a few cubic millimeters of volume. Each isothermal τ determination can take from minutes to several hours. We tested the method with two glasses of known viscosity values: borosilicate glass (VG98) and alumimoborosilicate glass (SG7), both of which are used for radioactive waste immobilization and have assigned log(η) values between 6 and 7.3 with η in Pa s. The discrepancy between the log(η) values assigned here and those values fitted with a VFT function on the values measured for the SG7 and VG98 glasses were within ±14%.

Viscosity and structure relaxation in Zr60Cu20Al10Ni10 metallic glass

This work reports the estimation of the viscosity, relaxation time and free volume of Zr60Cu20Al10Ni10 metallic glass (MG) by extrapolating differential scanning calorimetry (DSC), thermo-mechanical analyzer (TMA), and nanoindentation measurement data. The structural relaxation process of Zr60Cu20Al10Ni10 MG is shown through the study of viscosity and relaxation behavior also displayed by these measurements. It has the ability to exhibit strong fluid behavior near the glass transition temperature and exhibits a large strength parameter of 26.9 and a Vogel-Fulcher-Tamman temperature of 378 K. At the same time its stress relaxation exhibits sensitivity to strain rate and paused load. Finally, we estimated the residual free volume from melt freezing inside the Zr60Cu20Al10Ni10 MG by DSC technique as 0.041. These results indicate that the Zr60Cu20Al10Ni10 MG has a large free volume and exhibits both strong fluidic properties and significant stress relaxation behavior.

Room Temperature Viscous Flow of Amorphous Silica Induced by Electron Beam Irradiation.

The increasing use of oxide glasses in high-tech applications illustrates the demand of novel engineering techniques on nano- and microscale. Due to the high viscosity of oxide glasses at room temperature, shaping operations are usually performed at temperatures close or beyond the point of glass transition Tg . Those treatments, however, are global and affect the whole component. It is known from the literature that electron irradiation facilitates the viscous flow of amorphous silica near room temperature for nanoscale components. At the micrometer scale, however, a comprehensive study on this topic is still pending. In the present study, electron irradiation inducing viscous flow at room temperature is observed using a micropillar compression approach and amorphous silica as a model system. A comparison to high temperature yielding up to a temperature of 1100 °C demonstrates that even moderate electron irradiation resembles the mechanical response of 600 °C and beyond. As an extreme case, a yield strength as low as 300MPa is observed with a viscosity indicating that Tg has been passed. Those results show that electron irradiation-facilitated viscous flow is not limited to the nanoscale which offers great potential for local microengineering.

Physical Properties and Low-Frequency Polarizability Anisotropy and Dipole Responses of Phosphonium Bis(fluorosulfonyl)amide Ionic Liquids with Pentyl, Ethoxyethyl, or 2-(Ethylthio)ethyl Group

This study compared the physical properties, e.g., glass transition temperature, melting point, viscosity, density, surface tension, and electrical conductivity, and the low-frequency spectra under 200 cm-1 of three synthesized ionic liquids (ILs), triethylpentylphosphonium bis(fluorosulfonyl)amide ([P2225][NF2]), ethoxyethyltriethylphosphonium bis(fluorosulfonyl)amide ([P222(2O2)][NF2]), and triethyl[2-(ethylthio)ethyl]phosphonium bis(fluorosulfonyl)amide ([P222(2S2)][NF2]), at various temperatures using femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES) and terahertz time-domain spectroscopy (THz-TDS). The [P222(2S2)][NF2] had the highest viscosity and glass transition temperature, whereas the [P222(2O2)][NF2] had the lowest. Among the three ILs, the [P222(2S2)][NF2] had the highest density and surface tension, and the [P222(2O2)][NF2] had the highest electrical conductivity. The RIKES and THz-TDS spectral line shapes for the three ILs varied significantly. For the [P2225][NF2], molecular dynamics simulations successfully reproduced the line shapes of the experimental spectra and indicated that the RIKES spectrum was mainly due to the cation and cross-term and their rotational motions, whereas the THz-TDS spectrum was mainly due to the anion and its translational motion. This shows that it is desirable to utilize both fs-RIKES and THz-TDS methods to reveal molecular motions at the low-frequency domain. The [P222(2S2)][NF2] had higher frequency peaks and broader bands in the low-frequency spectra via fs-RIKES and THz-TDS than those for the [P2225][NF2] and [P222(2O2)][NF2].

Mathematical modeling of a three-component system to investigate the formation and characteristics of glass

The article investigates glass formation and its properties in a three-component system using mathematical modeling. The authors have applied the method of mathematical planning to increase the efficiency of research and to establish the dependences of glass properties on the composition. The authors propose a mathematical model of structure relaxation and two-dimensional stress field in grade glass products, considering the temperature dependencies of glass viscosity of a given chemical composition.

Unsteady axisymmetric flow of nanofluid on nonlinearly expanding surface with variable fluid properties

The physical phenomena of nanofluid at high temperature motivate us to analyze problems with temperature-reliant fluid properties, like viscosity and thermal conductivity. Since in glass blowing, viscosity and thermal conductivity of the fluid may gets affected in such high temperature. This communication deals with the unsteady flow of nanofluid generated by nonlinear expansion of the surface. Temperature-dependent fluid viscosity and thermal conductivity are considered in the investigation of the problem. The flow of nanofluid is modeled using famous the Buongiorno's two-phase model, which includes the simultaneous effect of Brownian motion and thermophoresis diffusion. Appropriate transformations are adopted to obtain the ODEs from governing PDEs. Then MATLAB ‘bvp4c’ computation is used to solve the problem and to get a clear insight of the influences of various parameters. Graphical comparisons are made to check the accuracy of used numerical method. The study explores that heat transfer rate significantly enhances by the index of nonlinearity, variable viscosity and thermal conductivity parameters. Unsteadiness of the flow can be used as a controlling parameter to reduce the surface drag, heat and nano-mass transfer rate. Variable viscosity parameter leads to enhance the velocity near the surface and reducing the concentration of the nanoparticles. The thermal and concentration boundary layer thickens with thermal conductivity parameters. Nanofluid temperature and concentration of nanoparticles decay with nonlinear expanding index.

High-performance carbon nanofiber reinforced epoxy-based nanocomposite adhesive materials modified with novel functionalization method and triblock copolymer

New high-performance epoxy-based nanocomposite adhesive materials were developed with the innovative use of nanomaterials to enhance the bond strength, especially at elevated temperatures. A tetraglycidyl diaminodiphenylmethane (TGDDM) based aerospace-grade epoxy adhesive (EA9396) with a high glass transition temperature and viscosity was combined with functionalized CNFs and a phase-separated poly(styrene)-poly(butadiene)-poly(methyl methacrylate) triblock copolymer (SBM). The ozone-treated CNFs (OZ-CNFs) were functionalized with polyethyleneimine dendrimer (PEI + OZ-CNFs), or a polyamine hardener (H + OZ-CNFs) and characterized using X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) to confirm the chemical reaction of the amine functional groups. Room temperature mechanical testing revealed the optimized nanocomposite adhesives containing SBM and CNFs functionalized with either PEI or hardener resulted in a 40% increase in lap shear strength (50 MPa) when compared to the unmodified epoxy (35.6 MPa). At the elevated temperature of 90 °C, a strength improvement of 35% and 38% (29.5 MPa and 30 MPa) was observed for the adhesives containing SBM and CNFs functionalized using PEI or hardener, respectively. SEM images showed that CNF functionalization provided a more uniform distribution in the adhesive and enhanced the SBM plastic deformation during crack propagation. The PEI and hardener functionalization also significantly reduced the level of CNF pull-out, which was believed to enhance the energy dissipation mechanisms responsible for the significant increase in the lap shear strength.

Effect of SiO2 content on the oxidation resistance of SiO2–B4C-glass coating for alumina–carbon refractories

To improve the oxidation resistance of alumina–carbon refractories, SiO2–B4C-glass composite coating was prepared by slurry brushing method on the surface of refractories. Effect of SiO2 content on the oxidation resistance of the coating was studied. Oxidation resistance mechanism and failure reason of the SiO2–B4C-glass coating were discussed. Results showed that introducing SiO2 could increase viscosity activation energy and elevate the glass layer's viscosity at high temperature. With the increase of SiO2 content, the glass viscosity at high temperature gradually increased. When SiO2 content was too low, the glass exhibited smaller viscosity and larger fluidity, so the glass layer was easy to be washed away. When SiO2 content was too high, the glass phase with high viscosity and low fluidity could not uniformly cover on the surface of alumina–carbon refractories. The composite coating with SiO2 content of 55 wt% exhibited excellent oxidation resistance, which could effectively protect alumina–carbon refractories at 800 °C for 100 h with weight loss of only −1.721%. Excellent oxidation resistance of the coating mainly depended on the glass layer with good self-healing ability. With the extension of oxidation time, the coating thickness decreased, leading to the relatively poor self-healing ability and reduced weight gain rate of the coating.

Investigation on the anti-aging properties enhancement mechanism of graphene on RA based on size effect

The application of rubber powder to modify asphalt has become one of the main ways of resourceful and harmless utilization of waste tire rubber. However, rubber powder is prone to degradation during service, and this deficiency limits its further development. To solve the problem of insufficient aging resistance of RA, multi-layer graphene with different sizes was adopted to modify it. The aging resistance of modified asphalt was evaluated by high-temperature dynamic shear test(DSR), low-temperature bending beam test (BBR), and Brookfield rotational viscosity test (RV), and the microscopic mechanism was investigated by Fourier infrared spectroscopy (FTIR) and Four-component analysis(SARA). Furthermore, the aging model of modified asphalt was established by combining the content of asphalt components and the number of oxidation functional groups using MD technology, to reveal the size effect and anti-aging mechanism of graphene from a molecular perspective. In the molecular simulation section, the radial distribution function (RDF), mean square displacement (MSD), glass transition temperature (TG), and viscosity of the model were compared and analyzed. Macroscopic tests showed that graphene could improve the rheological properties and viscosity of RA, and the graphene with a smaller size has a more obvious improvement of asphalt anti-aging properties. Comparing the carbonyl index and carboxyl index of the four components before and after asphalt aging, it can be found that, graphene mainly relies on the inhibition of the oxidation of saturated phenols to improve the aging resistance of asphalt. In further simulation analysis, the glass transition behavior and viscosity simulation of the asphalt model confirmed the above conclusion and further revealed that the modification mechanism of graphene is related to its size. The high surface of small-sized graphene adsorbs more light components and forms a "micelle core", which inhibits the tendency of resin, aromatic, and asphaltene rearrangement during aging. In addition, graphene increases the energy within asphalt molecules and decreases the energy between asphalt molecules, which leads to more active intermolecular motion and promotes uniform dispersion of asphalt micelles in the dispersion medium. This research can offer a theoretical guideline for optimizing the use of graphene in modified asphalt.

Evaluation of Bioactive Glass and Low Viscosity Resin as Orthodontic Enamel Sealer: An In Vitro Study.

The study aimed to evaluate the effect of applying fluoride bioactive glass (FBAG) and Alpha-Glaze® (resin sealer) on the shear bond strength of orthodontic brackets to enamel bonded by Transbond XT, brushing‒abrasion durability, and their protective effect against simulated cariogenic acidic attack. Materials include 135 extracted premolars that were divided into three groups-FBAG, Alpha-Glaze, and control. The shear bond strength test was measured using an Instron Universal Testing Machine. The brushing abrasion challenge took place with a tooth-brushing simulator. Transmitted light microscopy examinations were performed after the specimens were demineralized for 4 days. The results show that the shear bond strength values of the three groups did not report any statistically significant differences: FBAG (28.1 ± 5.5 Mpa), Alpha-Glaze (32.5 ± 7.4 Mpa), and control (30.7 ± 6.5 Mpa) p &lt; 0.05. The Adhesive Remenant Index (ARI) study showed chipping of enamel in 6.6% of Alpha-Glaze and control specimens and 40% of specimens had their enamel surface covered with resin. Furthermore, 30% of the FBAG and 100% of the Alpha-Glaze sealer specimens resisted the abrasion test. In conclusion, FBAG can serve as an orthodontic-sealer capable of protecting the enamel surface surrounding orthodontic brackets. However, the Alpha-Glaze sealer did not offer the capability of protecting the enamel.