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We report an investigation of the effect of benzil and cobalt stearate on the degradation behaviour of LDPE films. Thin films (70 μ) containing these additives were prepared by sheeting process. The effect of heating, exposure to UV-B and... more
We report an investigation of the effect of benzil and cobalt stearate on the degradation behaviour of LDPE films. Thin films (70 μ) containing these additives were prepared by sheeting process. The effect of heating, exposure to UV-B and natural weathering of LDPE films in ...
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Melamine has shown broad utility as a flame retardant in plastics although its commercial use to date as a flame retardant additive has been principally in coatings and flexible urethane foams. Its mode of action appears to involve... more
Melamine has shown broad utility as a flame retardant in plastics although its commercial use to date as a flame retardant additive has been principally in coatings and flexible urethane foams. Its mode of action appears to involve endothermic sublimation and vapor-phase dissociation, but it also undergoes conversion to non-volatile products and ammonia. Combinations of melamine with other flame retardants of all types have been reported as hav ing advantageous performance. The present review covers the patent and non- patent literature with 130 references.**
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ABSTRACT Isocyanate-terminated urethane prepolymer was prepared by reacting 2 mol of tolylene diisocyanate (TDI) with 1 mol of hydroxy-terminated polybutadiene (HTPB, mol. wt. = 3000) at room temperature (30 ± 1°C) in the presence of... more
ABSTRACT Isocyanate-terminated urethane prepolymer was prepared by reacting 2 mol of tolylene diisocyanate (TDI) with 1 mol of hydroxy-terminated polybutadiene (HTPB, mol. wt. = 3000) at room temperature (30 ± 1°C) in the presence of stannous octoate as the catalyst. Urethane prepolymer was subsequently mixed with 1,4-butane diol: glycerol (6 : 1 ratio), methyl methacrylate (MMA), and ethylene glycol dimethacrylate (EGDMA) to give an interpenetrating polymer network. Stannous octoate was used as a catalyst to give network I, and azobisisobutyronitrile (AIBN), as an initiator to give network II. Different proportions of MMA were added to the prepolymer for studying the effect of composition on mechanical properties, thermal behavior, and optical properties. The mechanothermal behavior was analyzed using a dynamic mechanical thermal analyzer. Tensile strength and modulus decreased with decreasing MMA content, whereas percent elongation at break increased. Thermal stability of the sample increased with increasing urethane content. © 1993 John Wiley & Sons, Inc.
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The paper describes the fabrication of cast acrylic sheets by copolymerizing a prepolymer syrup of methyl methacrylate (MMA) with varying amounts (1‐20 wt.‐%) of 2‐ethylhexyl methacrylate (EHMA), n‐hexyl methacrylate (HMA), 2‐ethylhexyl... more
The paper describes the fabrication of cast acrylic sheets by copolymerizing a prepolymer syrup of methyl methacrylate (MMA) with varying amounts (1‐20 wt.‐%) of 2‐ethylhexyl methacrylate (EHMA), n‐hexyl methacrylate (HMA), 2‐ethylhexyl acrylate (EHA) and n‐hexyl acrylate (HA). The effect of structure of copolymer on light transmittance, density and mechanical properties was evaluated. Tensile strength and storage modulus decreased with increasing comonomer content. Strain increased significantly in the case of MMA/EHA and MMA/HA copolymer sheets having 15 and 20 wt.‐% of comonomer. Softening temperature of copolymer samples was determined using dynamic mechanical thermal analysis. Heat deflection temperature under flexural load and softening temperature decreased with increasing comonomer content in copolymer.
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Urethane methacrylate monomer (UMA) containing methacryloyl group was prepared from toluylene diisocyanate (TDI), 2‐hydroxyethyl methacrylate (HEMA), and ethylene glycol by a two step reaction. Curing was investigated using benzoyl... more
Urethane methacrylate monomer (UMA) containing methacryloyl group was prepared from toluylene diisocyanate (TDI), 2‐hydroxyethyl methacrylate (HEMA), and ethylene glycol by a two step reaction. Curing was investigated using benzoyl peroxide and N,N‐dimethylaniline as initiator system. The effect of concentration of initiator and reactive diluents, i.e., methyl methacrylate and styrene, on gel point was determined. An increase in gel time was observed by increasing the concentration of reactive diluent or decreasing the concentration of initiator. In TG traces (recorded in nitrogen atmosphere) of cured resins two step decomposition was observed in the temperature range of 230 to 500°C. The thermal stability of copolymers was influenced by the nature and content of reactive diluent.
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The effect of commercially available stabilizers such as Tinuvin‐327, Tinuvin‐770, and Irganox‐1024 on the photooxidation of polystyrene (PS) was investigated by following the changes in molecular weight and molecular weight distribution.... more
The effect of commercially available stabilizers such as Tinuvin‐327, Tinuvin‐770, and Irganox‐1024 on the photooxidation of polystyrene (PS) was investigated by following the changes in molecular weight and molecular weight distribution. Structural changes during degradation were studied by 1H‐NMR‐ and IR‐Spectroscopy and by Electron Spectroscopy for Chemical Analysis (ESCA). Neat PS films became very brittle and yellow on exposure to UV light. Tinuvin‐770 stabilized the PS films towards discolouration and brittleness.The ESCA studies of surface photooxidation of polystyrene indicate the formation of ketonic and methylene ether groups in the initial stages (˜ 100 h). At later stages ester and carbonate groups are formed.
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The relative effectiveness of five commercially available stabilizers on the photooxidation and thermal ageing of polypropylene (PP) was investigated by following changes in mechanical properties. Samples of PP containing different... more
The relative effectiveness of five commercially available stabilizers on the photooxidation and thermal ageing of polypropylene (PP) was investigated by following changes in mechanical properties. Samples of PP containing different percentages of Cyasorb UV‐531 were prepared (designated as PC0.5‐31, PC1‐31, PC1.5‐31, and PC2‐31, respectively). The effect of photooxidation on thermal behaviour was investigated by differential scanning calorimetry and thermogravimetric analysis. 2‐Hydroxy‐4‐n‐octyloxy benzophenone (2% w/w) was most effective in stabilizing PP towards discolouration and brittleness. After 32 h irradiation, 81% retention in yield strength was observed in case of PC1‐31 against 18% in case of PP.
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The paper deals with the effect of addition of bis(allylphenyl) type (TM 120) monomer on the properties of unidirectionally carbon fibre reinforced 4,4′ bismaleimidodi‐phenyl methane (BM) – 2,4‐tolylene diamine (A) (1:0.3 molar ratio)... more
The paper deals with the effect of addition of bis(allylphenyl) type (TM 120) monomer on the properties of unidirectionally carbon fibre reinforced 4,4′ bismaleimidodi‐phenyl methane (BM) – 2,4‐tolylene diamine (A) (1:0.3 molar ratio) (BM‐A) composites. The curing and thermal behaviour of the blends was investigated by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) in air atmosphere. A marginal decrease in thermal stability was observed with increasing concentration of TM 120. Flexural, interlaminar, and impact strength of the laminates increased in the presence of this monomer. Optimum mechanical properties were observed at ∼ 20 phr of TM 120.
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The paper describes the effect of styrene on the properties of bis(methacryloxy) derivatives of epoxy resins (vinyl ester resins). The styrene concentration in the resin was systematically varied between 20–60 wt.‐%. The curing... more
The paper describes the effect of styrene on the properties of bis(methacryloxy) derivatives of epoxy resins (vinyl ester resins). The styrene concentration in the resin was systematically varied between 20–60 wt.‐%. The curing characteristics of vinyl ester resins changed only marginally on dilution with styrene. Dilution with styrene resulted in a decrease in tensile modulus and increase in elongation of neat resin castings and glass fibre reinforced laminates. The glass transition temperature of laminates was determined by dynamic mechanical analysis and was found to decrease with increasing styrene content.
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Research Interests: Materials Engineering, Condensed Matter Physics, Chemistry, Conducting Polymers, Medicine, and 12 moreCorrosion, Polymerization, Electrochemical Impedance Spectroscopy, AFM, Dielectric Spectroscopy, Electrical Conductivity, EIS, Charge transfer, Reaction Mechanism, Naphthalene, Copolymer, and The Lancet
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... Vishal Anand,; Veena Choudhary. ... Greater amounts of N-aryl itaconimides could be incorporated into copolymers, which was difficult to attain with maleimides having a similar structure. ... 1 Patel, JD; Patel, MR J Macromol Sci Chem... more
... Vishal Anand,; Veena Choudhary. ... Greater amounts of N-aryl itaconimides could be incorporated into copolymers, which was difficult to attain with maleimides having a similar structure. ... 1 Patel, JD; Patel, MR J Macromol Sci Chem 1983, A19, 801. ...
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Melt rheology and morphology of ternary blends of polypropylene/high density polyethylene (PP/HDPE) ( ) and ethylene-propylene-diene (EPDM) terpolymer were investigated using an Instron capillary rheometer and Weissenberg rheogoniometer.... more
Melt rheology and morphology of ternary blends of polypropylene/high density polyethylene (PP/HDPE) ( ) and ethylene-propylene-diene (EPDM) terpolymer were investigated using an Instron capillary rheometer and Weissenberg rheogoniometer. The effect of temperature ...
Research Interests: Engineering, Materials Science, Rheology, Morphology, Polymer, and 13 moreNatural rubber, Theoretical Morphology (in Biology), Temperature, Activation Energy, Polypropylene, Composite Material, CHEMICAL SCIENCES, Impact Strength, High Density Polyethylene, Epdm Rubber, Tensile Strength, Young Modulus, and Mechanical Property
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The study represents synthesis, characterization and biological evaluation of redox responsive polymeric nanoparticles based on random multiblock copolymer for doxorubicin delivery in breast cancer. The random multiblock copolymer was... more
The study represents synthesis, characterization and biological evaluation of redox responsive polymeric nanoparticles based on random multiblock copolymer for doxorubicin delivery in breast cancer. The random multiblock copolymer was synthesized via ring opening polymerization of lactide with polyethylene glycol to form triblock copolymer followed by isomerization polymerization of the triblock copolymer and 2-hydroxyethyl disulfide with the help of hexamethylene diisocynate in presence of dibutyltin dilaurate as a catalyst. Folic acid was conjugated to hydroxyl group from the multiblock polymer through DCC-NHS coupling. High drug loading content of ∼22% was achieved in the polymeric nanoparticles with size range of ∼110nm and polyethylene glycol fraction of ∼18% in the multiblock copolymer. Drug release profile confirmed the redox responsive behavior of polymeric nanoparticles with ∼72% drug release at pH 5.5 in presence of 10mM GSH as compared to ∼18% drug release at pH 7.4. In vitro cellular uptake studies showed ∼22% cellular uptake with dual (folic acid and trastuzumab) conjugated polymeric nanoparticles as compared to non-targeted polymeric nanoparticles. Fluorescence activated cell sorting (FACS) studies demonstrated higher apoptosis (∼80%) as compared to non-conjugated polymeric nanoparticles (20%) in MCF-7 cell line. In vivo studies showed 91% tumor regression in Ehrlich ascites tumor (EAT) as compared to free doxorubicin treated mice without showing any significant toxicity. Thus, it is envisaged that these redox responsive polymeric nanocarriers act as Trojan horses in cancer therapeutics.
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The aim of this work was the development of a versatile route for the preparation of temperature‐ and pH‐responsive hydrogels with small dimensions. The copolymerization of N,N‐dimethylaminoethyl methacrylate with various amounts (5 and... more
The aim of this work was the development of a versatile route for the preparation of temperature‐ and pH‐responsive hydrogels with small dimensions. The copolymerization of N,N‐dimethylaminoethyl methacrylate with various amounts (5 and 10 mol %) of dimethylmaleimidoethyl methacrylate in solution with 2,2′‐azobisisobutyronitrile as an initiator is described. The structural and molecular characterization of the copolymers was performed with proton nuclear magnetic resonance, Fourier transform infrared, and ultraviolet spectroscopy, as well as size exclusion chromatography. Differential scanning calorimetry and thermogravimetry were used for the thermal characterization of the copolymers. Micro‐ and nanohydrogels of the copolymers were prepared by photocrosslinking. The gels obtained by photocrosslinking were characterized with a combination of surface plasmon resonance and optical waveguide spectroscopy, dynamic light scattering, and scanning electron microscopy. The hydrogels showed temperature‐ and pH‐responsive behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 669–679, 2007
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Abstract This paper reviews the recent studies of extraction of nanocellulose (cellulose nanofibers, nanocrystals, nanowhiskers, nanocrystalline cellulose, etc.) from sugarcane bagasse as agro-waste by different extraction methods such as... more
Abstract This paper reviews the recent studies of extraction of nanocellulose (cellulose nanofibers, nanocrystals, nanowhiskers, nanocrystalline cellulose, etc.) from sugarcane bagasse as agro-waste by different extraction methods such as acid-hydrolysis, alkaline-hydrolysis, enzymatic-hydrolysis, sonication, high-pressure homogenization, and shear ultrafine friction grinding, disk-grinder, including potential applications. Keywords: Sugarcane bagasse, nanocellulose, nanofibres, nanocrystals, acid-hydrolysis
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Graft copolymerization of acrylic acid on to polypropylene filaments was investigated by a simultaneous irradiation technique. The effect of various solvents and solvent combinations on swelling behaviour and on percentage grafting was... more
Graft copolymerization of acrylic acid on to polypropylene filaments was investigated by a simultaneous irradiation technique. The effect of various solvents and solvent combinations on swelling behaviour and on percentage grafting was studied. At a constant dose, the percentage grafting was found to be higher at low dose rates and it increased linearly up to 0.25 Mrad and then saturated. It was also observed that grafting increases with increasing monomer concentration up to 2 mole/litre. Graft copolymers were characterized by infrared spectroscopy and colour formation with methylene blue.
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Research Interests: Engineering, Materials Science, Polymer Chemistry, Morphology, Polymerization, and 11 moreSuzuki Miyaura cross-coupling, Block Copolymer, Polymer, Nanostructure, Controlled/living Radical Polymerization, CHEMICAL SCIENCES, Molecular weight, Copolymer, Block Copolymers, Molecular Weight Distribution, and Styrene
ABSTRACT This paper investigates rheological and mechanical properties of poly(trimethylene terephthalate) (PTT) in presence of multi-walled carbon nanotubes (MWCNTs). Morphological characterization by scanning electron microscope and... more
ABSTRACT This paper investigates rheological and mechanical properties of poly(trimethylene terephthalate) (PTT) in presence of multi-walled carbon nanotubes (MWCNTs). Morphological characterization by scanning electron microscope and transmission electron microscope showed uniform distribution of MWCNTs in the PTT matrix. Incorporation of MWCNTs into PTT matrix resulted in higher complex viscosity (η), storage (G′) and loss modulus (G″) than those of neat PTT, especially in low-frequency region. The dramatic increase in melt viscosity of PTT observed upon incorporation of MWCNTs in the range of 0.25–1 wt% could be due to the formation of interconnected network of MWCNTs in the polymer matrix, and thus, this can be regarded as rheological percolation threshold concentration. Cole–Cole plot showed change in slope and also shift in G′ versus G″ plot, which suggested change in microstructure upon MWCNT addition. The reinforcing effect of MWCNTs was also confirmed by dynamic mechanical analysis, where, by adding CNTs, a noticeable increase in storage modulus of PTT was observed. However, addition of MWCNTs showed no significant effect on the tensile properties of PTT due to poor interfacial interaction between CNTs and polymer matrix.
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ABSTRACT Multiwalled carbon nanotubes (MWCNTs) were synthesized using chemical vapor deposition and poly(trimethylene terephthalate) (PTT)/MWCNT composites with varying amounts of MWCNTs were prepared by melt compounding using DSM... more
ABSTRACT Multiwalled carbon nanotubes (MWCNTs) were synthesized using chemical vapor deposition and poly(trimethylene terephthalate) (PTT)/MWCNT composites with varying amounts of MWCNTs were prepared by melt compounding using DSM micro-compounder. Morphological characterization by SEM and TEM showed uniform dispersion of MWCNTs in PTT matrix upto 2% (w/w) MWCNT loading. Incorporation of MWCNTs showed no effect on percent crystallinity but affected the crystallite dimensions and increased the crystallization temperature. Dynamic mechanical characterization of composites showed an increase in storage modulus of PTT upon incorporation of MWCNTs above glass transition temperature. The electrical conductivity of PTT/MWCNT composites increased upon incorporation of MWCNTs and percolation threshold concentration was obtained at a loading of MWCNTs in the range of 1–1.5% (w/w). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
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This article reports the detailed study of dynamic mechanical properties of multiwalled carbon nanotubes/poly(ether ketone) nanocomposites prepared by melt blending. The dynamic mechanical characterisitic parameters such as storage... more
This article reports the detailed study of dynamic mechanical properties of multiwalled carbon nanotubes/poly(ether ketone) nanocomposites prepared by melt blending. The dynamic mechanical characterisitic parameters such as storage modulus (E′), loss modulus (E″) and damping factor (tan δ) were explored in detail to investigate the adhesion factor (A), strength factor (B), efficiency factor (C), and entanglement density (N). Adhesion factor, which is inversely related to the degree of interaction between nanotubes and matrix, decreased with increase in MWCNT loading. Strength factor (B) which is a direct measure of interaction between MWCNTs and PEK increased with increase in MWCNT loading. The effect of nanotubes on moduli of composites is calculated in terms of coefficient of reinforcement (C factor). Lower is the value of coefficient (C) higher will be the effectiveness of reinforcement on moduli of composites. It decreased from value of 1 at 1 wt% MWCNTs loading in PEK to 0.67 at 5 wt% MWCNTs loading which point towards increased effectiveness of MWCNTs at 5 wt% loading for excellent properties. To compliment these findings, entanglement density (N) was also calculated. Furthermore, Cole–Cole analysis was carried out to demonstrate the compatibility of both the components in composite system. POLYM. COMPOS., 39:2587–2596, 2018. © 2016 Society of Plastics Engineers
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The paper describes the synthesis of block copolymers of methyl methacrylate (MMA) and N‐aryl itaconimides using atom‐transfer radical polymerization (ATRP) via a poly(methyl methacrylate)–Cl/CuBr/bipyridine initiating system or a reverse... more
The paper describes the synthesis of block copolymers of methyl methacrylate (MMA) and N‐aryl itaconimides using atom‐transfer radical polymerization (ATRP) via a poly(methyl methacrylate)–Cl/CuBr/bipyridine initiating system or a reverse ATRP AIBN/FeCl3·6H2O/PPh3 initiating system. Poly(methyl methacrylate) (PMMA) macroinitiator, ie with a chlorine chain‐end (PMMA‐Cl), having a predetermined molecular weight (Mn = 1.27 × 104 g mol−1) and narrow polydispersity index (PDI = 1.29) was prepared using AIBN/FeCl3·6H2O/PPh3, which was then used to polymerize N‐aryl itaconimides. Increase in molecular weight with little effect on polydispersity was observed on polymerization of N‐aryl itaconimides using the PMMA‐Cl/CuBr/Bpy initiating system. Only oligomeric blocks of N‐aryl itaconimides could be incorporated in the PMMA backbone. High molecular weight copolymer with a narrow PDI (1.43) could be prepared using tosyl chloride (TsCl) as an initiator and CuBr/bipyridine as catalyst when a mixture of MMA and N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 was used. Thermal characterization was performed using differential scanning calorimetry (DSC) and dynamic thermogravimetry. DSC traces of the block copolymers showed two shifts in base‐line in some of the block copolymers; the first transition corresponds to the glass transition temperature of PMMA and second transition corresponds to the glass transition temperature of poly(N‐aryl itaconimides). A copolymer obtained by taking a mixture of monomers ie MMA:N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 showed a single glass transition temperature. Copyright © 2005 Society of Chemical Industry
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Research Interests: Engineering, Chemical Engineering, Chemistry, Polymer Chemistry, Kinetics, and 12 moreExperimental Design, Polymerization, Optimization, Emulsion polymerization, Factorial Design, CHEMICAL SCIENCES, Monomer, Particle Size, Methyl Methacrylate, Emulsion, Journal of Applied Polymer Science, and Pulmonary Surfactant
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... Nimisha Agarwal,; Abhishek Singh,; Indra K. Varma,; Veena Choudhary. Article first published online: 30 JAN 2008. ... 5 Malik, M.;Choudhary, V.;Varma, IK In Proceedings of the Conference on Thermophysical Properties of Materials;... more
... Nimisha Agarwal,; Abhishek Singh,; Indra K. Varma,; Veena Choudhary. Article first published online: 30 JAN 2008. ... 5 Malik, M.;Choudhary, V.;Varma, IK In Proceedings of the Conference on Thermophysical Properties of Materials; Hing, P., Ed.; Singapore, 1999; p 249. ...
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ABSTRACT In the present paper poly(methyl methacrylate) (PMMA)/multiwall carbon nanotubes (MWCNT) nanocomposites were prepared by bulk polymerization of MMA in presence of varying amounts of MWCNT and 2-hydroxyethyl methacrylate (HEMA)... more
ABSTRACT In the present paper poly(methyl methacrylate) (PMMA)/multiwall carbon nanotubes (MWCNT) nanocomposites were prepared by bulk polymerization of MMA in presence of varying amounts of MWCNT and 2-hydroxyethyl methacrylate (HEMA) modified MWCNT (HCNT) using azobisisobutyronitrile (AIBN) as an initiator. The nanocomposites were characterized for their structural, thermal, electrical and morphological behaviour using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The presence of nanofiller inhibits the formation of head to head linkages as all the nanocomposite samples show two step degradation whereas PMMA prepared under similar condition showed three step degradation. The glass transition temperature (Tg) of PMMA increased after incorporation of MWCNTs. The obtained nanocomposites show an increasing trend in the molecular weight with increase in the wt % of MWCNT whereas it decreases with the increasing initiator concentration. It was observed that the electrical conductivity is the function of molecular weight of the polymer as well as the content of MWCNT in the nanocomposites. The electrical conductivity of PMMA/HCNT composites was slightly lower as compared to PMMA/MWCNT whereas an increasing trend in the storage modulus of PMMA/HCNT nanocomposites was observed.