Different biological methods are gaining recognition for the production of silver nanoparticles (Ag-NPs) due to their multiple applications. The use of plants in the green synthesis of nanoparticles emerges as a cost effective and eco-friendly approach. In this study the green biosynthesis of silver nanoparticles using Callicarpa maingayi stem bark extract has been reported. Characterizations of nanoparticles were done using different methods, which include; ultraviolet-visible spectroscopy (UV-Vis), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDXF) spectrometry, zeta potential measurements and Fourier transform infrared (FT-IR) spectroscopy. UV-visible spectrum of the aqueous medium containing silver nanoparticles showed absorption peak at around 456 nm. The TEM study showed that mean diameter and standard deviation for the formation of silver nanoparticles were 12.40 ± 3.27 nm. The XRD study showed that the particles are crystalline in nature, with a face centered cubic (fcc) structure. The most needed outcome of this work will be the development of value added products from Callicarpa maingayi for biomedical and nanotechnology based industries.
The current status of silver nanoparticles (AgNPs) in the water environment in Malaysia was examined and reported. For inspection, two rivers and two sewage treatment plants (STPs) were selected. Two activated carbons derived from oil palm (ACfOPS) and coconut (ACfCS) shells were proposed as the adsorbent to remove AgNPs. It was found that the concentrations of AgNPs in the rivers and STPs are in the ranges of 0.13 to 10.16 mg L-1 and 0.13 to 20.02 mg L-1, respectively, with the highest concentration measured in July. ACfOPS and ACfCS removed up to 99.6 and 99.9% of AgNPs, respectively, from the water. The interaction mechanism between AgNPs and the activated carbon surface employed in this work was mainly the electrostatic force interaction via binding Ag+ with O- presented in the activated carbon to form AgO. Fifteen kinetic models were compared statistically to describe the removal of AgNPs. It was found that the experimental adsorption data can be best described using the mixed 1,2-order model. Therefore, this model has the potential to be a candidate for a general model to describe AgNPs adsorption using numerous materials, its validation of which has been confirmed with other material data from previous works.
In this work, quantum chemical analysis was used to predict the degradation potential of a recalcitrant dye, Acid blue 113, by hydrogen peroxide, ozone, hydroxyl radical and sulfate radical. Geometry optimization and frequency calculations were performed at 'Hartree Fock', 'Becke, 3-parameter, Lee-Yang-Parr' and 'Modified Perdew-Wang exchange combined with PW91 correlation' levels of study using 6-31G* and 6-31G** basis sets. The Fourier Transform-Raman spectra of Acid blue 113 were recorded and a complete analysis on vibrational assignment and fundamental modes of model compound was performed. Natural bond orbital analysis revealed that Acid blue 113 has a highly stable structure due to strong intermolecular and intra-molecular interactions. Mulliken charge distribution and molecular electrostatic potential map of the dye also showed a strong influence of functional groups on the neighboring atoms. Subsequently, the reactivity of the dye towards the oxidants was compared based on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy values. The results showed that Acid blue 113 with a HOMO value -5.227 eV exhibits a nucleophilic characteristic, with a high propensity to be degraded by ozone and hydroxyl radical due to their lower HOMO-LUMO energy gaps of 4.99 and 4.22 eV respectively. On the other hand, sulfate radical and hydrogen peroxide exhibit higher HOMO-LUMO energy gaps of 7.92 eV and 8.10 eV respectively, indicating their lower reactivity towards Acid blue 113. We conclude that oxidation processes based on hydroxyl radical and ozone would offer a more viable option for the degradation of Acid blue 113. This study shows that quantum chemical analysis can assist in selecting appropriate advanced oxidation processes for the treatment of textile effluent.
In the present study, the construction of arrays on silicon for naked-eye detection of DNA dengue was demonstrated. The array was created by exposing a polyethylene glycol (PEG) silane monolayer to 254 nm ultraviolet (UV) light through a photomask. Formation of the PEG silane monolayer and photomodifed surface properties was thoroughly characterized by using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The results of XPS confirmed that irradiation of ultraviolet (UV) light generates an aldehyde functional group that offers conjugation sites of amino DNA probe for detection of a specific dengue virus target DNA. Employing a gold enhancement process after inducing the electrostatic interaction between positively charged gold nanoparticles and the negatively charged target DNA hybridized to the DNA capture probe allowed to visualize the array with naked eye. The developed arrays demonstrated excellent performance in diagnosis of dengue with a detection limit as low as 10 pM. The selectivity of DNA arrays was also examined using a single base mismatch and noncomplementary target DNA.
Inactivation constant for V79 cells has been extracted from radiobiology experiments that utilize charged particles to irradiate mammal cells in vitro. Physical parameters such as effective charge, radiation mean free path and linear ionization which characterized protons and heluim-4 particles are determined using of standard values. The relationship between inactivation constant α and physical quality parameters have been determined, in this research, for protons and heluim-4 particles. This approach allows getting the characteristic biological response of inactivation of V79 cells in terms of each selected physical quality parameter. The best regression models are formulated for each obtained relationship.
Copper ion recognition and DNA interaction of a newly synthesized fluorescent Schiff base (HPyETSC) were investigated using UV-vis and fluorescent spectroscopy. Examination using these two techniques revealed that the detection of copper by HPyETSC is highly sensitive and selective, with a detection limit of 0.39 μm and the mode of interaction between HPyETSC and DNA is electrostatic, with a binding constant of 8.97×10(4) M(-1). Furthermore, gel electrophoresis studies showed that HPyETSC exhibited nuclease activity through oxidative pathway.
The main physical properties of ferroelectric crystals are described, and the macroscopic and microscopic viewpoints are discussed along with some applications, such as in capacitors and nonlinear optics. The emphasis is on physical understanding, while the mathematical level is kept to a minimum or supplemented by graphical representations to make the article more accessible.
Erythromycin A and roxithromycin are clinically important macrolide antibiotics that selectively act on the bacterial 50S large ribosomal subunit to inhibit bacteria's protein elongation process by blocking the exit tunnel for the nascent peptide away from ribosome. The detailed molecular mechanism of macrolide binding is yet to be elucidated as it is currently known to the most general idea only. In this study, molecular dynamics (MD) simulation was employed to study their interaction at the molecular level, and the binding free energies for both systems were calculated using the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method. The calculated binding free energies for both systems were slightly overestimated compared to the experimental values, but individual energy terms enabled better understanding in the binding for both systems. Decomposition of results into residue basis was able to show the contribution of each residue at the binding pocket toward the binding affinity of macrolides and hence identified several key interacting residues that were in agreement with previous experimental and computational data. Results also indicated the contributions from van der Waals are more important and significant than electrostatic contribution in the binding of macrolides to the binding pocket. The findings from this study are expected to contribute to the understanding of a detailed mechanism of action in a quantitative matter and thus assisting in the development of a safer macrolide antibiotic.
FT-IR spectrum of (2E)-3-(3-nitrophenyl)-1-[4-piperidin-1-yl]prop-2-en-1-one was recorded and analyzed. The vibrational wavenumbers were computed using HF and DFT quantum chemical calculations. The data obtained from wavenumber calculations are used to assign IR bands. Potential energy distribution was done using GAR2PED software. The geometrical parameters of the title compound are in agreement with the XRD results. NBO analysis, HOMO-LUMO, first and second hyperpolarizability and molecular electrostatic potential results are also reported. The possible electrophile attacking sites of the title molecule is identified using MEP surface plot study. Molecular docking results predicted the anti-leishmanic activity for the compound.
To reduce undesirable charging effects in scanning electron microscope images, Rayleigh contrast stretching is developed and employed. First, re-scaling is performed on the input image histograms with Rayleigh algorithm. Then, contrast stretching or contrast adjustment is implemented to improve the images while reducing the contrast charging artifacts. This technique has been compared to some existing histogram equalization (HE) extension techniques: recursive sub-image HE, contrast stretching dynamic HE, multipeak HE and recursive mean separate HE. Other post processing methods, such as wavelet approach, spatial filtering, and exponential contrast stretching, are compared as well. Overall, the proposed method produces better image compensation in reducing charging artifacts.
The title compound, 2C14H14N4O·H2O, comprises a neutral mol-ecule containing a central pyrazol-3-one ring flanked by an N-bound phenyl group and a C-bound 5-methyl-1H-pyrazol-3-yl group (at positions adjacent to the carbonyl substituent), its zwitterionic tautomer, whereby the N-bound proton of the central ring is now resident on the pendant ring, and a water mol-ecule of crystallization. Besides systematic variations in geometric parameters, the two independent organic mol-ecules have broadly similar conformations, as seen in the dihedral angle between the five-membered rings [9.72 (9)° for the neutral mol-ecule and 3.32 (9)° for the zwitterionic tautomer] and in the dihedral angles between the central and pendant five-membered rings [28.19 (8) and 20.96 (8)° (neutral mol-ecule); 11.33 (9) and 11.81 (9)°]. In the crystal, pyrazolyl-N-H⋯O(carbon-yl) and pyrazolium-N-H⋯N(pyrazol-yl) hydrogen bonds between the independent organic mol-ecules give rise to non-symmetric nine-membered {⋯HNNH⋯NC3O} and {⋯HNN⋯HNC3O} synthons, which differ in the positions of the N-bound H atoms. These aggregates are connected into a supra-molecular layer in the bc plane by water-O-H⋯N(pyrazolide), water-O-H⋯O(carbon-yl) and pyrazolyl-N-H⋯O(water) hydrogen bonding. The layers are linked into a three-dimensional architecture by methyl-C-H⋯π(phen-yl) inter-actions. The different inter-actions, in particular the weaker contacts, formed by the organic mol-ecules are clearly evident in the calculated Hirshfeld surfaces, and the calculated electrostatic potentials differentiate the tautomers.
The title compound, C13H10N2O2 [also called 1-(pyridin-2-yl)-3-(pyridin-3-yl)propane-1,3-dione], features an almost planar (r.m.s. deviation = 0.0095 Å) central C3O2 core consolidated by an intra-molecular hy-droxy-O-H⋯O(carbon-yl) hydrogen bond. Twists are evident in the mol-ecule, as seen in the dihedral angles between the central core and the 2- and pyridin-3-yl rings of 8.91 (7) and 15.88 (6)°, respectively. The conformation about the C=C bond [1.3931 (17) Å] is Z, and the N atoms lie to the same side of the mol-ecule. In the mol-ecular packing, supra-molecular chains along the a axis are mediated by π(pyridin-2-yl)-π(pyridin-3-yl) inter-actions [inter-centroid distance = 3.7662 (9) Å]. The observation that chains pack with no directional inter-actions between them is consistent with the calculated electrostatic potential, which indicates that repulsive inter-actions dominate.
A novel disposable electrochemical biosensor based on immobilized calf thymus double-stranded DNA (dsDNA) on the carbon-based screen-printed electrode (SPE) is developed for rapid biorecognition of carrageenan by using methylene blue (MB) redox indicator. The biosensor protocol for the detection of carrageenan is based on the concept of competitive binding of positively charged MB to the negatively charged dsDNA and carrageenan. The decrement in the MB cathodic peak current (ipc) signal as a result of the released MB from the immobilized dsDNA, and attracted to the carrageenan can be monitored via differential pulse voltammetry (DPV). The biosensor showed high sensitivity and selectivity to carrageenan at low concentration without interference from other polyanions such as alginate, gum arabic and starch. Calibration of the biosensor with carrageenan exhibited an excellent linear dependence from 1-10 mg L-1 (R2 = 0.98) with a detection limit of 0.08 mg L-1. The DNA-based carrageenan biosensor showed satisfactory reproducibility with 5.6-6.9% (n = 3) relative standard deviations (RSD), and possessing several advantages such as simplicity, fast and direct application to real sample analysis without any prior extensive sample treatments, particularly for seaweeds and food analyses.
Fish oil-in-water emulsions containing fish oil, thiol-modified β-lactoglobulin (β-LG) fibrils, chitosan and maltodextrin were fabricated using a high-energy method. The results showed that chitosan coating induced charge reversal; denoting successful biopolymers complexation. A significantly (p<0.05) larger droplet size and lower polydispersity index value, attributed to the thicker chitosan coating at the oil-water interface, were observed. At high chitosan concentrations, the cationic nature of chitosan strengthened the electrostatic repulsion between the droplets, thus conferring high oxidative stability and low turbidity loss rate to the emulsions. The apparent viscosity of emulsions stabilized using thiol-modified β-LG fibrils-chitosan complex was higher than those stabilized using β-LG fibrils alone, resulting in the former's higher creaming stability. Under thermal treatments (63°C and 100°C), emulsions stabilized using thiol-modified β-LG fibrils-chitosan complex possessed higher heat stability as indicated by the consistent droplet sizes observed. Chitosan provided a thicker protective layer that protected the oil droplets against high temperature. Bridging flocculation occurred at low chitosan concentration (0.1%, w/w), as revealed through microscopic observations which indicated the presence of large flocs. All in all, this work provided us with a better understanding of the application of protein fibrils-polysaccharide complex to produce stable emulsion.
This study presents an investigation on the effect of shield placement for mitigation of transient voltage in a 33/11 kV, 30 MVA transformer due to Standard Switching Impulse (SSI) and Oscillating Switching Impulse (OSI) surges. Generally, the winding and insulation in transformers could experience severe voltage stress due to the external impulses i.e. switching events. Hence, it is important to examine the voltage stress and identify the mitigation action i.e. shield placements in order to reduce the adverse effect to the transformer windings. First, the resistances, inductances, and capacitances (RLC) were calculated for disc type transformer in order to develop the winding RLC equivalent circuit. The SSI and OSI transient voltage waveforms were applied to the High Voltage (HV) winding whereby the transient voltages were simulated for each disc. The resulting voltage stresses were mitigated through different configurations of electrostatic shield placements. The resonant oscillations generated due to switching surges were analysed through initial voltage distribution. The analyses on the transient voltages of the transformer winding and standard error of the slope (SEb) reveal that the location of shield placement has a significant effect on the resonant switching voltages. The increment of the shield number in the windings does not guarantee optimize mitigation of the resonant switching transient voltages. It is found that the voltage stress along the windings is linear once a floating shield is placed between the HV and Low Voltage (LV) windings of the disc-type transformer under the SSI and OSI waveforms. These findings could assist the manufacturers with appropriate technical basis for mitigation of the transformer winding against the external transient switching overvoltage surges.
This paper proposes an alternative approach to extract transformer's winding parameters of resistance (R), inductance (L), capacitance (C) and conductance (G) based on Finite Element Method (FEM). The capacitance and conductance were computed based on Fast Multiple Method (FMM) and Method of Moment (MoM) through quasi-electrostatics approach. The AC resistances and inductances were computed based on MoM through quasi-magnetostatics approach. Maxwell's equations were used to compute the DC resistances and inductances. Based on the FEM computed parameters, the frequency response of the winding was obtained through the Bode plot function. The simulated frequency response by FEM model was compared with the simulated frequency response based on the Multi-conductor Transmission Line (MTL) model and the measured frequency response of a 33/11 kV, 30 MVA transformer. The statistical indices such as Root Mean Square Error (RMSE) and Absolute Sum of Logarithmic Error (ASLE) were used to analyze the performance of the proposed FEM model. It is found that the simulated frequency response by FEM model is quite close to measured frequency response at low and mid frequency regions as compared to simulated frequency response by MTL model based on RMSE and ASLE analysis.
This paper presents a unique synergistic behavior between a graphene oxide (GO) and graphene nanoplatelet (GnP) composite in an aqueous medium. The results showed that GO stabilized GnP colloid near its isoelectric point and prevented rapid agglomeration and sedimentation. It was considered that a rarely encountered charge-dependent electrostatic interaction between the highly charged GO and weakly charged GnP particles kept GnP suspended at its rapid coagulation and phase separation pH. Sedimentation and transmission electron microscope (TEM) micrograph images revealed the evidence of highly stable colloidal mixtures while zeta potential measurement provided semi-quantitative explanation on the mechanism of stabilization. GnP suspension was confirmed via UV-vis spectral data while contact angle measurement elucidated the close resemblance to an aqueous solution indicating the ability of GO to mediate the flocculation prone GnP colloids. About a tenfold increase in viscosity was recorded at a low shear rate in comparison to an individual GO solution due to a strong interaction manifested between participating colloids. An optimum level of mixing ratio between the two constituents was also obtained. These new findings related to an interaction between charge-based graphitic carbon materials would open new avenues for further exploration on the enhancement of both GO and GnP functionalities particularly in mechanical and electrical domains.
Curdlan (CN)-doped montmorillonite/poly(N-isopropylacrylamide-co-N,N'-methylene-bis-acrylamide) [CN/MT/P(NIPA-co-MBA)] smart nanocomposites (NCs) were developed for efficient erlotinib HCl (ERL) delivery to lung cancer cells. The placebo NCs demonstrated excellent biodegradability, pH/thermo-responsive swelling profiles and declined molar mass (M¯c) between the crosslinks with increasing temperature. The XRD, FTIR, DSC, TGA, and SEM analyses revealed the architectural chemistry of these NC scaffolds. The NCs loaded with ERL (F-1-F-3) displayed acceptable diameter (734-1120 nm) and zeta potential (+1.16 to -11.17 mV), outstanding drug entrapping capability (DEE, 78-99%) and sustained biphasic ERL elution patterns (Q8h, 53-91%). The ERL release kinetics of the optimal matrices (F-3) obeyed Higuchi model and their transport occurred through anomalous diffusion. The mucin adsorption behaviour of these matrices followed Freudlich isotherms. As compared to pure ERL, the formulation (F-3) displayed an improved anti-proliferative potential and induced apoptosis more effectively on A549 cells. Thus, the CN-doped smart NCs could be utilized as promising drug-cargoes for lung cancer therapy.
Therapies with magnetic/electromagnetic field are employed to relieve pains or, to accelerate flow of blood-particles, particularly during the surgery. In this paper, a theoretical study of the blood flow along with particles suspension through capillary was made by the electro-magneto-hydrodynamic approach. Analytical solutions to the non-dimensional blood velocity and non-dimensional particles velocity are obtained by means of the Laplace transform with respect to the time variable and the finite Hankel transform with respect to the radial coordinate. The study of thermally transfer characteristics is based on the energy equation for two-phase thermal transport of blood and particles suspension with viscous dissipation, the volumetric heat generation due to Joule heating effect and electromagnetic couple effect. The solution of the nonlinear heat transfer problem is derived by using the velocity field and the integral transform method. The influence of dimensionless system parameters like the electrokinetic width, the Hartman number, Prandtl number, the coefficient of heat generation due to Joule heating and Eckert number on the velocity and temperature fields was studied using the Mathcad software. Results are presented by graphical illustrations.
Three sorbent materials (A18C6-MS, DA18C6-MS and AB18C6-MS) based on the crown ether ligands, 1-aza-18-crown-6, 1,4,10,13-tetraoxa-7,16-diazacyclo octadecane and 4'-aminobenzo-18-crown-6, respectively, were prepared by the chemical immobilization of the ligand onto mesoporous silica support. The sorbents were characterized by FT-IR, scanning electron microscopy-energy dispersive X-ray microanalysis, elemental analysis and nitrogen adsorption-desorption test. The applicability of the sorbents for the extraction of biogenic amines by the batch sorption method was extensively studied and evaluated as a function of pH, biogenic amines concentration, contact time and reusability. Under the optimized conditions, all the sorbents exhibited highest selectivity toward spermidine (SPD) compared to other biogenic amines (tryptamine, putrescine, histamine and tyramine). Among the sorbents, AB18C6-MS offer the highest capacity and best selectivity towards SPD in the presence of other biogenic amines. The AB18C6-MS sorbent can be repeatedly used three times as there was no significant degradation in the extraction of the biogenic amines (%E>85). The optimized procedure was successfully applied for the separation of SPD in food samples prior to the reversed-phase high performance liquid chromatography separation.