Diabetes patients are at risk of having chronic wounds, which would take months to years to resolve naturally. Chronic wounds can be countered using the electrical stimulation technique (EST) by dielectrophoresis (DEP), which is label-free, highly sensitive, and selective for particle trajectory. In this study, we focus on the validation of polystyrene particles of 3.2 and 4.8 μm to predict the behavior of keratinocytes to estimate their crossover frequency (fXO) using the DEP force (FDEP) for particle manipulation. MyDEP is a piece of java-based stand-alone software used to consider the dielectric particle response to AC electric fields and analyzes the electrical properties of biological cells. The prototypic 3.2 and 4.8 μm polystyrene particles have fXO values from MyDEP of 425.02 and 275.37 kHz, respectively. Fibroblast cells were also subjected to numerical analysis because the interaction of keratinocytes and fibroblast cells is essential for wound healing. Consequently, the predicted fXO from the MyDEP plot for keratinocyte and fibroblast cells are 510.53 and 28.10 MHz, respectively. The finite element method (FEM) is utilized to compute the electric field intensity and particle trajectory based on DEP and drag forces. Moreover, the particle trajectories are quantified in a high and low conductive medium. To justify the simulation, further DEP experiments are carried out by applying a non-uniform electric field to a mixture of different sizes of polystyrene particles and keratinocyte cells, and these results are well agreed. The alive keratinocyte cells exhibit NDEP force in a highly conductive medium from 100 kHz to 25 MHz. 2D/3D motion analysis software (DIPP-MotionV) can also perform image analysis of keratinocyte cells and evaluate the average speed, acceleration, and trajectory position. The resultant NDEP force can align the keratinocyte cells in the wound site upon suitable applied frequency. Thus, MyDEP estimates the Clausius-Mossotti factors (CMF), FEM computes the cell trajectory, and the experimental results of prototypic polystyrene particles are well correlated and provide an optimistic response towards keratinocyte cells for rapid wound healing applications.
Recovery of chemicals and fuels from unrecyclable waste plastics at high temperatures (>800 °C) has received much research attention. Thermodynamic equilibrium calculation suggests that it is possible to perform the low-temperature steam reforming of polystyrene. In this study, we synthesized a Ni-Fe bimetallic catalyst for the low-temperature (500 °C) steam reforming of polystyrene. XRD characterization showed that Ni-Fe alloy was formed in the catalyst. Compared to conventional Ni catalysts, the Ni-Fe bimetallic catalysts can significantly increase the H2/CO ratio in the produced gas with high gas production yield. The online gas analysis revealed that H2, CO, and CO2 were formed in the same temperature range. H2 and CO were formed simultaneously through steam reforming reactions, and CO2 was formed through water-gas shift reaction. New morphologies of carbon deposition on the catalyst surface were found, suggesting that wax could be condensed on the catalyst surface at a low temperature.
The continuous fragmentation of plastics and release of synthetic nanoplastics from products have been aggravating nanoplastic pollution in the marine ecosystem. The carrier role of nanoplastics may increase the bioavailability and toxicity effects of toxic metals, e.g., mercury (Hg), which is of growing concern. Here, the copepod Tigriopus japonicus was exposed to polystyrene nanoplastics (PS NPs) and Hg (alone or combined) at environmental realistic concentrations for three generations (F0-F2). Then, Hg accumulation, physiological endpoints, and transcriptome were analyzed. The results showed that the copepod's reproduction was significantly inhibited under PS NPs or Hg exposure. The presence of PS NPs caused significantly higher Hg accumulation, lower survival, and lower offspring production in copepods relative to Hg exposure, suggesting an increased threat to the copepod's survivorship and health. From the molecular perspective, combined PS NPs and Hg caused a graver effect on the DNA replication, cell cycle, and reproduction pathways relative to Hg exposure, linking to lower levels of survivorship and reproduction. Taken together, this study provides an early warning of nanoplastic pollution for the marine ecosystem not only because of their adverse effect per se but also their carrier role for increasing Hg bioaccumulation and toxicity in copepods.
In-situ bioremediation of mangrove soil contaminated with polyethylene terephthalate (PET) and polystyrene (PS) microplastics was investigated using indigenous microbial consortium with adequate capacity to degrade the plastics. Eight (8) bacteria were isolated from plastic/microplastic-inundated mangrove soil and screened for the ability to degrade PET and PS microplastics. Optical density at 600 nm and colony forming unit counts were measured to evaluate the growth response of the microbes in the presence of PS and PET microplastics at different times of exposure. Structural and surface changes that occurred post biodegradation on the microplastics were determined through EDS and SEM analysis. The obtained results demonstrated the elongation and disappearance of peaks, suggesting that the microbial consortium could modify both types of microplastics. The overall results of the microplastic degradation showed varied degrees of weight loss after 90 experimental days, with the treated plot recorded 18% weight loss. The augmented soil was increased in the concentrations of Si S, and Fe and decreased in the concentrations of C, O, Na, Mg, Al, Cl, and K after bioremediation.
The direct determination of toxic metal ions, in environmental samples, is difficult because of the latter's presence in trace concentration in association with complex matrices, thereby leading to insufficient sensitivity and selectivity of the methods used. The simultaneous removal of the matrix and preconcentration of the metal ions, through solid phase extraction, serves as the promising solution. The mechanism involved in solid phase extraction (SPE) depends on the nature of the sorbent and analyte. Thus, SPE is carried out by means of adsorption, ion exchange, chelation, ion pair formation, and so forth. As polymeric supports, the commercially available Amberlite resins have been found very promising for designing chelating matrices due to its good physical and chemical properties such as porosity, high surface area, durability and purity. This review presents an overview of the various works done on the modification of Amberlite XAD resins with the objective of making it an efficient sorbent. The methods of modifications which are generally based on simple impregnation, sorption as chelates and chemical bonding have been discussed. The reported results, including the preconcentration limit, the detection limit, sorption capacity, preconcentration factors etc., have been reproduced.
Microplastics (MPs) have become pollutants of concern due to their unknown human health effect and negative impact on terrestrial and aquatic ecosystems. There is increasing number of experimental research on MPs globally with its effects not fully understood; recent animal studies explore its effects on the intestines, yet on other vital organs. Javanese medaka fish was exposed to polystyrene microplastics (PS-MPs) beads for a period of 21 days. Histological alterations, intestinal oxidative stress, permeability and neurotoxicity were evaluated. Significant inflammatory changes and tissue damage were observed in the intestine, liver and kidney. Intestinal oxidative stress and permeability were found to be significantly increased. In the brain, neurotoxicity characterised by a significant induction of oxidative stress, lipid peroxidation and the inhibition of acetylcholinesterase enzyme were elucidated. This study provided an insight into the multiple organ effect of microplastics exposure, necessitating further exploration and identification of biomarkers to be utilised for biomonitoring population at risk in the future.
The physical properties by natural fibre have a great importance, specifically in the structural of natural fibre which reinforces matrix. Response surface methodology with Box-Behnken (BB) design of experiment was utilized to study water absorption and melt flow index (MFI) of abaca fibre reinforced high impact polystyrene (HIPS) composites. The design utilizes fraction of weight abaca fibre, maleic anhydride (MAH), and impact modifier to develop models for characteristic behaviours of water absorption and MFI of composites. Abaca fibre reinforced high impact polystyrene (HIPS) composites were produced with different fibre loadings (30, 40, and 50 wt%), different compositions of coupling agent, maleic anhydried (MAH) (1, 2, and 3 wt%) and different compositions of impact modifier (4, 5, 6 wt%). The individual optimum of water absorption was found when loading abaca fibre close to 34.61 wt%, maleic anhydride 1 wt%, and impact modifier 4.01 wt%. The individual optimum of melt flow index dealt with loading abaca fibre 36.71 wt%, maleic anhydride 3 wt% and impact modifier 4.02 wt%. Meanwhile, the optimum condition for water absorption of abaca fibre reinforced HIPS composites was followed by a decreasing trend of the value of melt flow index.
This paper introduces a dielectrophoretic system for the manipulation and separation of microparticles. The system is composed of five layers and utilizes microarray dot electrodes. We validated our system by conducting size-dependent manipulation and separation experiments on 1, 5 and 15 μm polystyrene particles. Our findings confirm the capability of the proposed device to rapidly and efficiently manipulate and separate microparticles of various dimensions, utilizing positive and negative dielectrophoresis (DEP) effects. Larger size particles were repelled and concentrated in the center of the dot by negative DEP, while the smaller sizes were attracted and collected by the edge of the dot by positive DEP.
A detailed study on the conflicting role that colloid stability plays in magnetophoresis is presented. Magnetic iron oxide particles (MIOPs) that were sterically stabilized via surface modification with poly(sodium 4-styrene sulfonate) of different molecular weights (i.e., 70 and 1000 kDa) were employed as our model system. Both sedimentation kinetics and quartz crystal microbalance with dissipation (QCM-D) measurements suggested that PSS 70 kDa is a better stabilizer as compared to PSS 1000 kDa. This observation is mostly attributed to the bridging flocculation of PSS 1000 kDa decorated MIOPs originated from the extended polymeric conformation layer. Later, a lab-scale high gradient magnetic separation (HGMS) device was designed to study the magnetophoretic collection of MIOPs. Our experimental results revealed that the more colloidally stable the MIOP suspension is, the harder it is to be magnetically isolated by HGMS. At 50 mg/L, naked MIOPs without coating can be easily captured by HGMS at separation efficiency up to 96.9 ± 2.6%. However, the degree of separation dropped quite drastically to 83.1 ± 1.2% and 67.7 ± 4.6%, for MIOPs with PSS 1000k and PSS 70k coating, respectively. This observation clearly implies that polyelectrolyte coating that was usually employed to electrosterically stabilize a colloidal system in turn compromises the magnetic isolation efficiency. By artificially destroying the colloidal stability of the MIOPs with ionic strength increment, the ability for HGMS to recover the most stable suspension (i.e., PSS 70k-coated MIOPs) increased to >86% at 100 mM monovalent ion (Na(+)) or at 10 mM divalent ion (Ca(2+)). This observation has verified the conflicting role of colloidal stability in magnetophoretic separation.
A field trial of the use of expanded polystyrene beads (EPSB) to control the breeding of mosquito larvae in household septic tanks was conducted in Sarawak. One week after treatment, the breeding of Culex quinquefasciatus and Aedes albopictus was reduced by 100% and 68.7% respectively. For both species combined, a 57.25% reduction in the adult emergence rate was achieved. No adult was caught in the emergence trap one month after treatment. A reduction in mosquito biting rates was reported by 87.3% of respondents. All households regarded the EPSB treatment as effective. This study has reduced the relatively high infestation rate of A. albopictus in the septic tanks to 16-20%. The EPSB treatment is feasible and practical. Post-treatment assessment using adult emergence traps and the implications for the vector control programme of the local authority are discussed.
Monodispersed iron oxide nanoparticles (IONPs) coated with polystyrenesulfonate (PSS) and cetrimonium bromide (CTAB) have been used to stabilize magnetic Pickering emulsions (MPEs). Magnetophoresis of MPEs under the influence of a low gradient magnetic field (∇B < 100 T/m) was investigated at the macroscopic and microscopic scale. At the macroscopic scale, for the case of pH 7, the MPE achieved a magnetophoretic velocity of 70.9 μm/s under the influence of ∇B at 93.8 T/m. The magnetic separation efficiency of the MPE at 90% was achieved within 30 min for pH 3, 7, and 10. At pH 10, the colloidal stability of the MPE was the lowest compared to that for pH 3 and 7. Thus, MPE at pH 10 required the shortest time for achieving the highest separation efficiency, as the MPE experienced cooperative magnetophoresis at alkaline pH. The creaming rate of the MPE at all conditions was still lower compared to magnetophoresis and was negligible in influencing its separation kinetics profiles. At the microscopic scale, the migration pathways of the MPEs (with diameters between 2.5 and 7.5 μm) undergoing magnetophoresis at ∇B ∼ 13.0 T/m were recorded by an optical microscope. From these experiments, and taking into consideration the MPE size distribution from the dynamic light scattering (DLS) measurement, we determined the averaged microscopic magnetophoretic velocity to be 7.8 ± 5.5 μm/s. By making noncooperative magnetophoresis assumptions (with negligible interactions between the MPEs along their migration pathways), the calculated velocity of individual MPEs was 9.8 μm/s. Such a value was within the percentage error of the experimental result of 7.8 ± 5.5 μm/s. This finding allows for an easy and quick estimation of the magnetophoretic velocity of MPEs at the microscale by using macroscopic separation kinetics data.
Thermal characterization of sugar palm fibre (SPF), reinforced high impact polystyrene (HIPS)
composites, was studied by means of thermogravimetric analysis. The effects of alkaline treatment and compatibilizing agent on the thermal stability of the composites were evaluated. Alkaline treatment was carried out by soaking the fibres in 4 and 6% of NaOH solution, while treatment with compatibilizing agent was employed by adding 2 and 3% maleic anhydride-graft-polystyrene (MA-g-PS) to the composites. Both the treatments were aimed to improve the mechanical performance of the composites. From the study, the thermal stability of the treated composites was found to be higher than that of untreated composites. It is shown that the incorporation of sugar palm fibre influences the degree of thermal stability of the composites. The treatments on composites also contributed to shifting the peak temperature of degradation of the composites. In other words, there are strong chemical reactions between the components of the treated composites. The thermal stability of the composites, with alkaline treatment and compatibilizing agent, was found to be better as compared to those of the untreated composites.
Shotcrete is a process where concrete is projected or “shot” under pressure, using a feeder or a
“gun” onto a surface to form structural shapes including walls, floors, and roofs. The surface can
be wood, steel, polystyrene, or any other surfaces that concrete can be projected onto. The surface
can be trowel led smooth while the concrete is still wet. Shotcrete has high strength, durability, low
permeability, excellent bond, and limitless shape possibilities. These properties allow shotcrete
to be used as a structural material in most cases. Although the hardened properties of shotcrete
are similar to conventional cast-in-place concrete, the nature of the placement process provides
additional benefits, such as excellent bond with most substrates and instant or rapid capabilities,
particularly on complex forms or shapes. In addition to building homes, shotcrete can also be used
to build pools. The practice of underground tunneling shows that the degree of stability of tunnels
is dependent on the state of the soil, rock mass, and shotcrete around the tunnel contour. The
development in the urban or suburban areas leads to the construction of tunnels in all kinds of soil
and rock. Meanwhile, the construction of tunnels in shallow depth or soft soils causes the ground
to displace. The determination of soil and rock mechanical properties to assess the stability of New
Austrian Tunnelling Method (NATM) tunnels and design the support system is one of the most
important steps in tunnelling. This paper provides information pertaining to the safety and increase
the stability of NATM tunnel before, during and after the operation of the tunnel. Therefore, the
shotcrete process is a recognized method for cemented sandy silt stabilization, with the aid of high
pressure shot concrete to increase the stability of tunnels.
Response Surface Methodology (RSM) was used in the study to optimize the production of vanillin from isoeugenol through fermentation by Aspergillus niger I-1472. Three factors were studied which include amount of isoeugenol, resin (Amberlite XAD-4) and Span 80. During fermentation, isoeugenol as substrate were vortexed with Span 80 and added into the culture on Day 4. Resin (Amberlite XAD-4) was added into the medium the following day. The predicted optimum medium combination consisted of 3.61 g/L of isoeugenol, 5.8% (g/ mL) of Amberlite XAD-4 resin and 0.37% of Span 80 with an expected vanillin production of 0.137 g/L. Verification test showed that the model produced similar predicted and experimental values.
The purpose of this study is to compare the tensile strength between additional polystyrene into coconut meat husk reinforced fiber composite. Composite were produced by using hand layup technique. It is seen that with the additional of polystyrene into the coconut meat husk reinforced polyester composites showed the increment tensile strength value compared to the non-added polystyrene which indicates that effective stress transfer between the fiber, matrix and polystyrene.
Cellulose acetate (CA) is an interesting material due to its wide spectrum of utilities across different domains ranging from absorbent to membrane filters. In this study, polystyrene (PS) nanofibres, and cellulose acetate/polystyrene (CA/PS) blend nanofibres with various ratios of CA: PS from 20: 80 to 80: 20 were fabricated by using electrospinning technique. The SEM images show that the nanofibres exhibited non-uniform and random orientation with the average fibre diameter in the range of 100 to 800 nm. It was found that the incorporation of PS had a great effect on the morphology of nanofibre. At high proportion of PS, no or less beaded CA/PS nanofibres were formed. Thermal properties of the composite nanofibres were investigated by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. The TGA results showed thermal stability of CA/PS nanofibres were higher than pristine CA.
Here we use triple-cation metal-organic halide perovskite single crystals for the transistor channel of a flash memory device. Moreover, we design and demonstrate a 10 nm thick single-layer nanofloating gate. It consists of a ternary blend of two organic semiconductors, a p-type polyfluorene and an n-type fullerene that form a donor:acceptor interpenetrating network that serves as the charge storage unit, and of an insulating polystyrene that acts as the tunneling dielectric. Under such a framework, we realize the first non-volatile flash memory transistor based on a perovskite channel. This simplified, solution-processed perovskite flash memory displays unique performance metrics such as a large memory window of 30 V, an on/off ratio of 9 × 107, short write/erase times of 50 ms, and a satisfactory retention time exceeding 106 s. The realization of the first flash memory transistor using a single-crystal perovskite channel could be a valuable direction for perovskite electronics research.
An optical sensor for Hg(II) monitoring using a complex of zinc dithizonate immobilised on XAD 7 which is based on reflectance spectrophotometry has been developed in this study. Measurements were made using a kinetic approach whereby the reflectance signal is measured at a fixed time of 5 min. The sensor could be regenerated using a saturated solution of KCl in 1 M sulphuric acid. The sensor was found to have an optimum response at pH 3.0 with respective measurement repeatability and probe-to-probe reproducibility of 1.53% and 5.26%. A linear response was observed in the Hg(II) concentration range of 0.0-180.0 ppm with a calculated limit of detection (LOD) of 0.05 ppm. The results obtained for aqueous Hg(II) determination using this probe were found to be comparable with the well-established method of atomic absorption spectrometry.
Molecularly imprinted polymers (MIPs) were prepared by bulk polymerization in acetonitrile using 2,4-dinitrophenol, acrylamide, ethylene glycol dimethacrylate, and benzoyl peroxide, as the template, functional monomer, cross-linker, and initiator, respectively. The MIP membrane was prepared by hybridization of MIP particles with cellulose acetate (CA) and polystyrene (PS) after being ground and sieved. The prepared MIP membrane was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. The parameters studied for the removal of 2,4-dinitrophenol included the effect of pH, sorption kinetics, and the selectivity of the MIP membrane. Maximum sorption of 2,4-nitrophenol by the fabricated CA membrane with MIP (CA-MIP) and the PS membrane with MIP (PS-MIP) was observed at pH 7.0 and pH 5.0, respectively. The sorption of 2,4-dinitrophenol by CA-MIP and PS-MIP followed a pseudo-second-order kinetic model. For a selectivity study, 2,4-dichlorophenol, 3-chlorophenol, and phenol were selected as potential interferences. The sorption capability of CA-MIP and PS-MIP towards 2,4-dinitrophenol was observed to be higher than that of 2,4-dichlorophenol, 3-chlorophenol, or phenol.
Stem cell culture is typically based on batch-type culture, which is laborious and expensive. Here, we propose a continuous harvest method for stem cells cultured on thermoresponsive nanobrush surfaces. In this method, stem cells are partially detached from the nanobrush surface by reducing the temperature of the culture medium below the critical solution temperature needed for thermoresponse. The detached stem cells are harvested by exchange into fresh culture medium. Following this, the remaining cells are continuously cultured by expansion in fresh culture medium at 37 °C. Thermoresponsive nanobrush surfaces were prepared by coating block copolymers containing polystyrene (for hydrophobic anchoring onto culture dishes) with three types of polymers: (a) polyacrylic acid with cell-binding oligopeptides, (b) thermoresponsive poly-N-isopropylacrylamide, and (c) hydrophilic poly(ethyleneglycol)methacrylate. The optimal coating durations and compositions for these copolymers to facilitate adequate attachment and detachment of human adipose-derived stem cells (hADSCs) and embryonic stem cells (hESCs) were determined. hADSCs and hESCs were continuously harvested for 5 and 3 cycles, respectively, via the partial detachment of cells from thermoresponsive nanobrush surfaces.