•Enhancement of laccase secretion in B.brevis mediated PEMPs degradation.•Organic acids play significant role in B.brevis plastic degradation.•Increased crystallinity exposes bacterial consumption of ...amorphous phase of PEMPs.•Identification of dodecane and 2-hexadecanone reveal the CC bond cleavage of PEMPs.
The fragmentation of polyethylene plastics into polyethylene microplastics (PEMPs) due to biotic and abiotic factors affects the environment. Extensive investigations have shown its implications upon accumulation in the living systems. In this study, B.brevis was employed to degrade PEMPs. B.brevis-mediated degradation process has shown a reduction in microplastic's dry weight by 19.8% over 35 days of treatment. The biodegradation was achieved by releasing laccase enzyme and organic acids onto the surface of PEMPs, which were quantified by UP-HPLC. Further, the changes in the morphological and structural changes on of PEMPs were observed by TEM, SEM, DSC, TGA, XRD, and FTIR analysis. Additionally, after the degradation, by-products were observed to contain small molecules such as 2-hexadecanone, decanone etc. The small molecules were resulted from the biodegradation of PEMPs and were further utilized for bacterial metabolism. These outcomes reveal the efficiency of B.brevis in PEMPs degradation.
Polydioxanone is used in numerous medical applications, e.g., biodegradable sutures and implants, for its excellent biocompatibility and appropriate degradation time. However, detailed knowledge of ...the polydioxanone thermokinetic behavior is essential to achieve the required properties of the particular medical appliance produced. Differential scanning calorimetry (DSC) was used for thermokinetic characterization of polydioxanone. The study was focused on three phenomena associated with the amorphous/semi-crystalline state: structural relaxation, cold crystallization, and thermal degradation. The glass transition kinetics was described in terms of the Tool-Narayanaswamy-Moynihan model with the following parameters: Δh* = 679 kJ mol−1, log(A/s) = −311.76, β = 0.50, x = 0.45. The increasing degree of crystalline phase in the polymeric matrix led for the relaxation movements to a gradually decreasing dependence on structural arrangement. The cold crystallization of polydioxanone was described in terms of the autocatalytic Šesták-Berggren model with the following parameters: E = 95.2 kJ mol−1, log(A/s−1) = 15.04, MAC = 0.79, NAC = 0.70. The highest achieved amounts of crystalline phase differed between 53 and 63% depending on the route to the crystal formation (either the crystal growth from the melt during slow cooling or the growth from the fully amorphous phase during slow heating). The kinetic predictions based on the non-isothermal and isothermal crystallization data were found to be in good agreement. Thermal decomposition of polydioxanone starts at 190 °C via depolymerization to p-dioxanone monomer and consequent evaporation. However, the polydioxanone starts to partially depolymerize already at 150 °C, shortening its chains and decreasing average molecular weight. Based on the present thermokinetic characterization, the optimum processing conditions for polydioxanone production by means of hot melt extrusion and molding were discussed.
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•Thermokinetic characterization of polydioxanone was performed using DSC.•Glass transition kinetics was described in terms of TNM model.•Highest achieved degree of crystalline phase was 63 %.•PDX degrades via depolymerization and consequent evaporation.•PDX slowly depolymerizes already at 150 °C via unzipping mechanism.
•Spherical α-Fe2O3 nanoparticles have been synthesized using different precursors.•Iron oxide reduces the activation energy of the decomposition of nitrocellulose.•α-Fe2O3 nanoparticles affects the ...decomposition mechanism of nitrocellulose (NC).•Iron oxide produced from iron chloride is the best catalyst for NC.
In this study, α-Fe2O3 nanoparticles were successfully prepared by a simple and direct hydrothermal method using three different precursors (iron chloride, iron nitrate and iron sulphate). Structure and morphological characterization of the different nanoparticles have been investigated in detail by using a series of analytical methods including FTIR, Raman, XRD and SEM. The synthesized nanoparticles, predominately spherical in shape, have similar chemical structure, whatever the precursor employed. A higher crystallinity has been obtained for nanoparticles derived from iron chloride precursor, which present less agglomeration. The catalytic activity of as-prepared nanoparticles on the thermal decomposition of nitrocellulose (NC) was studied via differential scanning Calorimetry (DSC). Four isoconversional methods have been used to determine the kinetics triplets using the DSC data at different heating rates. It is revealed that the different nanocatalysts have a slight effect on the peak decomposition temperature of NC, whereas a notable decrease of the activation energy is obtained, especially for nanoparticles derived from iron chloride precursor. Finally, we can deduce that Fe2O3 prepared using iron chloride as a precursor may be safely used as an efficient catalyst for NC.
Curing behavior plays a key role in determining the ultimate properties of thermosetting polymers. With the use of fillers, curing behavior and reaction kinetics are affected. Here, we report the ...study of the curing process and thermal and mechanical behaviors of phenolic composites reinforced with 50 wt% of an economic filler, coal char. Curing kinetics were investigated using non-isothermal differential scanning calorimetry (DSC) measurements and analyzed by model-free isoconversional methods for determining kinetic parameters. The study revealed that the coal char had a retarding effect on the curing of the phenolic resin. The curing reaction was also influenced by the processing method of the composite. Mixing of the char in tetrahydrofuran (THF) led to higher activation energies than via dry mixing. The mechanical properties and thermal stability of the phenolic resin were significantly improved in the presence of the filler. The information reported in this work can be used for optimal curing of phenolic resin/coal char composites as well as tuning performance by choosing an appropriate processing technique.
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•Curing kinetics of phenolic resin/coal char composites was studied by differential scanning calorimetry (DSC).•The composites showed higher activation energies than the pure phenolic resin which retarded curing process.•Curing kinetics and performance of the composites were influenced by the processing technique.
Multicomponent borate glasses with the chemical composition (60−x) B2O3–10 Bi2O3–10 Al2O3–10 ZnO–10 Li2O–(x) Dy2O3 or Tb4O7 (x=0.5mol%), and (60−x−y) B2O3–10 Bi2O3–10 Al2O3–10 ZnO–10 Li2O–(x) ...Dy2O3–(y) Tb4O7 (x=0.25, 0.5, 0.75, 1.0, 1.5, and 2.0mol%, y=0.5mol%) have been fabricated by a conventional melt-quenching technique and were characterized by X-ray diffraction (XRD), Attenuated Total reflectance-Fourier transform Infrared (ATR-FTIR) spectroscopy, Raman spectroscopy, thermo-gravimetric analysis (TGA), and differential scanning calorimetry (DSC). Also, the radiation shielding parameters such as mass attenuation coefficient (μ/ρ), half value layer (HVL), mean free path (MFP) and exposure buildup factor (EBF) values were explored within the energy range 0.015MeV–15MeV using both XCOM and MCNPX code to determine the penetration of gamma and neutron radiations in the prepared glasses. The main BO3, BO4, BiO6, and ZnO4 structural units and AlOAl bonds were confirmed by ATR-FTIR and Raman spectroscopy. Weight loss, and the glass transition (Tg), onset crystallization (Tx), and crystallization (Tc) temperatures were determined from TGA and DSC measurements, respectively. The stability of the glass against crystallization (ΔT) is varied within the temperature range 114–135°C for the studied glasses. In addition, the shielding parameters like the (μ/ρ) values investigated using both MCNPX Monte Carlo and XCOM software are in good agreement with each other. The (μ/ρ) values calculated using XCOM software were used to evaluate the HVL and MFP in the photon energy range 0.015MeV–15MeV. It is found that all the synthesized glasses possess better shielding properties than ordinary concrete, zinc oxide soda lime silica glass and lead zinc phosphate glass indicating the high potentiality of the prepared glasses to be utilized as radiation shielding materials.
•Glasses in the system B2O3-Bi2O3-Al2O3-ZnO-Li2O-Dy2O3-Tb4O7 were synthesized.•Various functional groups were confirmed by both ATR-FTIR, and Raman spectroscopy.•All the synthesized glasses show good thermal stability with ΔT (=Tx−Tg)>100°C.•XCOM software and MCNPX simulation are used to calculate (μ/ρ) at different energies.•Geometric progression (GP) method was used to calculate the exposure buildup factors.
The green synthesis of nanoparticles has become a matter of great interest in recent times and proposed as an environmentally friendly alternative to chemical and physical methods. Blend of ...polyethylene oxide (PEO)/starch (70/30 wt%) doped with various concentrations of gold nanoparticles (Au NPs) were prepared by casting technique. X-ray diffraction (XRD) shows the semi-crystalline nature of all prepared samples. It also shows an increase in the amorphous region due to raising the doping level. Fourier Transform Infrared (FT-IR) spectra showed a change in intensities of OH groups and CH2 asymmetric stretching vibration after addition of gold nanoparticles, these changes were attributed to the interaction between polymeric matrix and Au NPs. Scanning electron microscopy (SEM) exhibited the partial compatibility between the polymer blend and the Au NPs. Differential scanning calorimetry (DSC) measurement indicated miscibility between the two polymers. The electrical properties were investigated via DC electrical conductivity, where found electrical conductivity increased as Au NPs content increased. The results suggest the choice of Au NPs as filler to enhance the electrical, optical, and thermal properties of PEO/starch blend.
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•Ricinus communis leaf extract was used for gold nanoparticles biosynthesis.•(PEO/Starch) blend/Au nanocomposites sample was prepared by a casting method.•XRD show the crystallinity degree decrease with increase of gold nanoparticles.•The optical parameters were improved after doping gold nanoparticles.•DC electrical measurements were increased after doping of gold nanoparticles.
•The dielectric response of a film-forming amine (OLDA) without electrolyte was investigated by broadband dielectric spectroscopy (BDS).•The OLDA dielectric contribution on electrochemical impedance ...spectra (EIS) was identified.•The impedance spectra (BDS and EIS) showed resistive and capacitive behaviours in mid and high frequency ranges, respectively.•In EIS, the high frequency capacitive response contains contributions of both the OLDA layer and the electrochemical double layer.•The gauche defects in the OLDA alkyl chain could facilitate ion and water infiltration in the adsorbed monolayer.
In this study, a detailed analysis of the dielectric response of a film-forming amine (1,3 N-oleyl propanediamine (OLDA)) in impedance spectra is presented, addressing both “bulk” OLDA and adsorbed OLDA layer on a carbon steel surface. The dielectric response of the “bulk” OLDA in the absence of electrolyte over an extensive temperature range (-150 °C to 50 °C) was explored by broadband dielectric spectroscopy (BDS). Subsequently, the response of the OLDA adsorbed layer on the steel surface was analysed by electrochemical impedance spectroscopy (EIS), for various immersion times (2 min to100 min) and temperatures (25 °C to 75 °C) in an aqueous NaCl solution.
Impedance spectra (BDS and EIS), interpreted through the complex conductivity formalism, showed a resistive behaviour in the mid-frequency range and a capacitive behaviour at higher frequencies. The high frequency capacitive response in EIS spectra was shown to contain contributions from the OLDA layer and from the electrochemical double layer, as well. The temperature dependency of the OLDA conductivity was found to be similar to the temperature dependency of the electrolyte resistance, suggesting that the electrolyte (water and ions) crossed the OLDA layer to reach the steel surface. The presence of gauche defects in the OLDA alkyl chain, revealed by polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) analyses, may be a contributing factor to the disorder in the adsorbed layer, facilitating electrolyte infiltration.
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We aimed to study the effect of conjugation with gum Arabic (GA) by Maillard reaction in aqueous solution on the structural properties of Canola protein isolate (CPI). First, the grafting of GA to ...CPI through Maillard reaction was confirmed by examination of the Fourier transform infrared spectra. The results showed that the thermal stability of CPI was remarkably improved by mixing or conjugating with GA. The evidence of particle size distribution determined by nanoparticles tracking analysis (NTA) confirmed that glycation can reduce the thermal aggregation and also nanoparticles of conjugate appear bigger than CPI. Furthermore, the tertiary structure of protein in conjugate changed with decreasing number of aromatic side-chains exposed in heating environment. The decrease in fluorescence intensity of conjugate was related to conformational changes due to presence of GA.
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•Glycation with gum Arabic improved thermal stability of canola protein isolate.•FTIR analysis confirmed grafting of canola protein isolate with gum Arabic.•The mean particle size value of samples measured by nanoparticle tracking analysis.•Intrinsic tryptophan fluorescence and tertiary structure of samples were evaluated.
This study is concerned with the design of multi-input Dynamic Surface Control (DSC) to dynamic stability improvement of power systems which include both Doubly Feed Induction Generator (DFIG) and ...Static Synchronous Series Compensator (SSSC). The presented control method has a multi-input feature which acts on synchronous generators. To improve dynamic stability, the control law is developed by applying a suitable Lyapunov function. The coefficients of the proposed controller are determined by use of metaheuristic optimization algorithms. This optimal control law leads to a significantly improved performance in comparison with linear control. A particular low-pass filter is also introduced and applied to cancel the effects of additional undesired terms in the design method, leading to a simplified control form compared to the other available approaches in the literature. Implementing an adaptive parameter estimation scheme will result in the robustness of the proposed method. The effectiveness of the presented approach is investigated on a standard 39-Bus power system which includes DFIG and SSSC.
This paper presents adaptive neural tracking control of underactuated surface vessels with modeling uncertainties and time-varying external disturbances, where the tracking errors consisting of ...position and orientation errors are required to keep inside their predefined feasible regions in which the controller singularity problem does not happen. To provide the preselected specifications on the transient and steady-state performances of the tracking errors, the boundary functions of the predefined regions are taken as exponentially decaying functions of time. The unknown external disturbances are estimated by disturbance observers and then are compensated in the feedforward control loop to improve the robustness against the disturbances. Based on the dynamic surface control technique, backstepping procedure, logarithmic barrier functions, and control Lyapunov synthesis, singularity-free controllers are presented to guarantee the satisfaction of predefined performance requirements. In addition to the nominal case when the accurate model of a marine vessel is known a priori, the modeling uncertainties in the form of unknown nonlinear functions are also discussed. Adaptive neural control with the compensations of modeling uncertainties and external disturbances is developed to achieve the boundedness of the signals in the closed-loop system with guaranteed transient and steady-state tracking performances. Simulation results show the performance of the vessel control systems.
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