Search

This study investigates the comparative effects of carboxyl-functionalized multi-walled carbon nanotube (MWCNT)/water nanofluids and titanium dioxide (TiO2) /water nanofluids in direct absorption parabolic solar collectors. To achieve this, a standard testing apparatus was constructed, and the thermal and exergy efficiencies of the collector were calculated using nanofluids at various concentrations. UV/Vis analysis was used to analyze the radiative properties of the nanofluids, and their thermal conductivity was also measured. Experiments were conducted under laminar flow conditions with flow rates of 20, 60, and 100 liters per hour and inlet temperatures of 20, 30, and 40 °C under real conditions with direct solar irradiation. The highest thermal efficiency recorded for the carbon-based nanofluid was 44.96%, while the titanium-based nanofluid achieved a thermal efficiency of 34.98%. Given the substantial improvement in efficiency compared to the base fluid (distilled water), the combined effect of using both nanofluids was also examined, resulting in a maximum thermal efficiency of 48.77%. The exergy efficiency at the highest flow rate and inlet temperature for the base fluid, TiO2 nanofluid, MWCNT nanofluid, and the hybrid nanofluid were 2.61%, 4.98%, 6.68%, and 7.26%, respectively. The pressure drop of all nanofluids in the absorber tube ranged from 5 to 39.6 Pascals. The studied nanofluids enhance the thermal performance of the system and create low pressure drop, indicating their high efficiency in direct absorption solar collectors. [ABSTRACT FROM AUTHOR]

A microbial fuel cell (MFC) is a device that converts chemical energy into electrical energy through the catalytic processes of microorganisms. In this study, flexible and porous WO3/CNTs-Graphite-PVC film was fabricated through uniform adding of Zn powder into matrix of carbon nanotubes-graphite-Polyvinyl Chloride) PVC ( film followed by selective dissolving of Zn from the film structure in acidic solution and finally electrodeposition of WO3 (Tungsten trioxide) into previously porous CNTs-Graphite-PVC film. Surface morphology studies showed that the flexible film has rough and porous structure and carbon nanotubes are uniformly present as electron conduction channels within the composite film. Studies also showed that porous WO3/MWCNTs-Graphite-PVC film as a bioanode in MFC at resistance of 1000 ohms and current density of 900 mA/m² has a power density of 324 mW/m². The method presented in this research can be used as a suitable method for preparing of suitable electrocatalysts based on commercial graphite powder in microbial fuel cells. [ABSTRACT FROM AUTHOR]

This study was carried out with the aim of covalent immobilization of Aspergillus oryzae beta-galactosidase and Bacillus licheniformis protease on multi-walled amino-carbon nanotubes. In this method, fractional 2k design was used to study the effect of seven continuous factors (activation pH, glutaraldehyde molarity, activation time, buffer solution pH, buffer solution molarity, MWCNT-NH3- glutaraldehyde amount and stabilization time) on the stabilization efficiency and enzyme activity. . Design-expert software was used to analyze data and draw graphs. The results showed that the aforementioned factors predict the level of enzyme activity of Bacillus licheniformis protease and Aspergillus oryzae betagalactosidase with correlation coefficients of 0.80 and 0.92 at the rate of 77 and 88%, respectively. Also, the correlation coefficient of the covalent fixation efficiency model of Aspergillus oryzae beta-galactosidase and Bacillus licheniformis protease on multi-walled carbon nanotubes was 0.89 and 0.82, respectively, and the studied factors were able to determine the covalent fixation beta efficiency, respectively. Aspergillus oryzae galactosidase and Bacillus licheniformis protease on multi-walled amino-carbon nanotubes predict 83 and 77%, respectively. [ABSTRACT FROM AUTHOR]

This paper deals with drilling of carbon fiber reinforced polymer (CFRP) composite filled with carbon nanotube (CNT) using response surface method (RSM) based utility function. In the drilling of CFRP composites with a hybrid metal base, the additional advance force and pleat height reduce the performance of the composite. Therefore, to improve the performance of the hybrid metal matrix composite, the advancing force and the pleat height of the composite are minimized. Hence, the advancing force and pleat height are the factors considered in the present research and are the main responses that are minimized using the RSM-based utility function. Four important input factors such as drilling speed, feed rate, CNT percentage and drill helix angle are considered to analyze the performance of the drilling process. The results showed that the advance rate is a very influential parameter that affects the advance force and pleat height in hybrid metal matrix composites. During the drilling operation, due to the mutual rubbing of the CNT abrasive particles, it causes extensive surface damage such as holes, cracks, and fibers coming out. The ANOVA results show that the experimental data are well correlated at the 95% confidence interval, and this technique can be very useful and reliable for predicting drilling parameters of CFRP metal matrix composites. [ABSTRACT FROM AUTHOR]

This research used multi-walled carbon nanotubes with a 30 to 50 nm diameter and an approximate length of 6 μm to store hydrogen gas by the volumetric method. Carbon nanotubes' structure, shape, and physical properties were investigated by X-ray diffraction analysis, transmission electron microscopy, and infrared spectroscopic analysis. To investigate the hydrogen storage capacity in carbon nanotubes, the effect of two parameters, namely acid washing and YAG: Nd laser irradiation, were studied. The results showed that acid washing and laser irradiation increased the specific surface area of carbon nanotubes by 59% and 100%, respectively. Studies also showed that purified carbon nanotubes stored 0.3 wt.% hydrogen, which revealed a 75% increase compared to the original nanotubes. Also, laser irradiation with different times changed the storage capacity of nanotubes. The optimal value of laser irradiation was obtained to be 90 minutes, which increased the storage capacity of hydrogen gas in nanotubes to 1.1 wt.%. [ABSTRACT FROM AUTHOR]

The effective Hamiltonian describing indirect exchange interactions of type Ruderman- Kittel-Kasuya-Yosida [RKKY] between the magnetic impurities near the Dirac Points is based on the first-order energy. Besides, the points where the impurities are located are important in identifying the oscillatory behaviour of these interactions. Then in this paper, we first intend to obtain the effective Hamiltonian elements near the Dirac points for 2D graphene structures using the tight-binding approximation and then the phase factors between neighbor Dirac points are noticed. The obtained results are extended to obtain the effective Hamiltonian and then the first-order energy for carbon nanotubes. Using the quantized wave vector in the circumferential direction of nanotubes at Dirac Points, we examine the condition for nanotubes to be metallic or semiconductors. The obtained results based on the tight binding could be used to study the magnetic interactions at low energy for graphene structures as well as carbon nanotubes.

After the discovery of carbon nanotubes, observations showed that carbon nanotubes have multi-purpose properties and can be used as a reinforcing material for metal nanocomposites. In this research, multi-walled carbon nanotubes have been used as nanocomposite reinforcement with Cu-5Zn alloy base. Carbon nanotubes were added to the nanocomposite in percentages of 0.25-1. Ultrasonic waves were used for good dispersion of carbon nanotubes in the field. Pressing and sintering processes were used to make nanocomposite samples. The microstructure was studied using a scanning electron microscope. The effect of carbon nanotubes on mechanical properties such as microhardness and tensile strength of nanocomposite was investigated. The results showed that the mechanical properties are improved by adding carbon nanotubes. The proposed mechanism for increasing the strength in nanocomposites reinforced with carbon nanotubes is the bridging mechanism. The microhardness of nanocomposites increases linearly with the increase of carbon nanotubes up to 0.75%, and the increase in hardness of nanocomposite with carbon nanotube reinforcing phase is 36% more than copper-zinc base alloy. The tensile strength of copper nanocomposites is 289 MPa by increasing the amount of carbon nanotube reinforcement, which is a significant increase compared to the base copper-zinc alloy with a strength of 165 MPa. [ABSTRACT FROM AUTHOR]

Wastewaters containing heavy metals produced by industries has detrimental effects on the environment. One of the effective methods for removal of heavy metals is the use of adsorption method by nanoparticles. The aim of this study was to remove zinc and nickel elements from effluents of Tarom industrial Town of Zanjan using modified multi-walled carbon nanotubes. In this descriptive-analytical study, effect of effective parameters such as contact time, adsorbent content, pH, temperature and concentration of metal ions on the removal efficiency of metals from Ni(II) and Zn(II) from wastewater and isotherm, kinetics and thermodynamic models of adsorption process was investigated. SEM and FTIR spectrums were taken to prove nanotubes and to determine adsorbent factor groups before and after preparation, respectively. The results of study showed that the absorption of Zn and Ni metals is highly dependent on pH. Study results showed that by increasing the pH of effluent up to the range of 8, and 7 for Ni(II) and Zn(II) metals, respectively, the removal percentage of metal ions increased and then decreased. By increasing in the adsorbent amount and contact time, the removal percentage of metal ions increased and by increasing the reaction temperature and concentration of metal ions in the effluent, the removal percentage of metal ions decreased. So that, the highest removal percentage of Ni(II) and Zn(II) ions was obtained in adsorbent value of 2 mg/L, contact time of 120 min, concentration of 100 mg/L and temperature of 15 °C. The results also showed that the adsorption of Ni(II) and Zn(II) metals from effluent follows Langmir isotherm absorption model and the adsorption kinetics is adapted to the second-order pseudo-reaction (R2>0.98), this mechanism is controlled by adsorption. Also, based on the obtained results, with increasing temperature, the free energy of Gibbs system standard decreased, which indicates the adsorption process is done spontaneously. The maximum adsorption capacity of nickel and zinc metals was 43 and 54 mg/g, respectively. According to the results, it is concluded that modified multi-walled carbon nanotubes have good ability to remove nickel and zinc from effluents and can be used in wastewater treatment containing heavy metals.

Recently, the use of carbon nanotubes in water treatment membranes has been proposed. Understanding the mechanism of the process in nanotubes may have a significant impact on the development of this technology. In this study, to clarify the molecular mechanism and measure the impact of the effective factors, the water desalination process by filters consisting of carbon nanotubes has been investigated by the molecular dynamics simulation method. The effect of factors such as nanotube diameter applied pressure and porosity on the process is studied. The results showed that reducing the filtration pressure increases salt rejection. However, reducing the pressure reduces the water flow through the nanotubes, which should be considered in the optimal design of the treatment system. Increasing the porosity of the membrane for a given nanotube does not have a significant effect on the desalination rate, but it greatly increases the flow rate. The simulation results showed that if the geometry studied in this study is used as a filter for nanotubes (10, 10), the flow rate of water at a pressure of 100 MPa will be equal to 7 mL/s per unit cross-section of the filter.

In the present study, the effect of magnetic field and electrospray on the orientation of carbon nanotubes (CNT), stabilized with COOH, in the obtained alginate/CNT adsorbent's matrix, as well as the adsorption of methylene blue, were investigated. FE-SEM and UV-visible spectroscopy were used to determine the characteristics and performance of absorbents. The images showed that the CNTs were significantly oriented in the polymer matrix by placing alginate-CNTs colloid in a magnetic field with an average strength of 318 mT for 2 h. While the spraying of colloidal droplets under the electric field had a negligible effect on the alignment of CNTs, it led to the size reduction of the droplets and an increase in the specific surface area of particles. By combining magnetic and electric fields in the presence of CNT, 92.2% of the methylene blue adsorption was obtained, which was higher than electrospray only (71%), and electrospray only without CNTs (59%). This research revealed that the orientation of carbon nanotubes under magnetic and electric fields was effective in increasing the adsorption efficiency of environmental pollutants and can lead to the production of more economical adsorbents. [ABSTRACT FROM AUTHOR]

The purpose of this research is to investigate the physical and mechanical properties of the wood-plastic nanocomposite made using Blank and Functionalized carbon nanotubes (CNTs). For this purpose, wood flour at a fixed amount of 50%, Blank CNTs at three levels of 0, 1 and 2% and coupling agent at two levels of 0 and 3% and the balance HDPE matrix were used. Also, Functionalized CNTS were used to strengthen the efficiency of nanocomposites at 1 and 2% levels separately. The materials were mixed in an internal mixer (Haake) and then the samples were made by a hot press machine. The results showed that by increasing the amount of CNTs from 0 to 2% wt, the tensile strength and modulus of the samples increased by 58.8% and 12.6% respectively, and water absorption and thickness swelling decreased by 54.5% and 19.4% respectively. Composites containing 2% wt of CNTs showed higher impact resistance compared to control samples. The coupling agent had a positive effect on the performance of nanocomposites. The physical and mechanical properties of the samples were significantly improved by adding the coupling agent and Functionalized CNTs. The results were also confirmed by scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Introduction Due to the rapid growth in the urban population, the numbers of cars also have increased which resulted in an increase of pollution level in the urban areas of the developing countries. The pollutants emerging from combustion engines may include: carbon monoxide (CO), unburned hydrocarbons (UBHC), oxide of nitrogen (NOx), oxides of sulfur (SOx), particulate matter (PM), soot, hydrogen, oxygen, traces of aldehydes, alcohols, ketons, phenols, acid, lead aerosol, etc., along with normal combustion products i.e. carbon dioxide (CO2) and water vapors. In order to overcome the problems associated with the bio-fuel, the chemical substances like fuel additives derived from organic, inorganic metals were used. Fuel additives generally improve the combustion efficiency and reduce the pollution. Metallic based compounds, such as manganese, iron, copper, barium, calcium and platinum, etc., which have been used as a combustion catalyst for hydrocarbon fuels. Recent advances in nanoscience and nanotechnology enables production, control and characterization of nanoscale energetic materials. Nano materials are more effective than bulk materials because of its higher surface area. Another important advantage of nanoparticle is its size, because there is no chance for fuel injector and filter clogging as in the case of micron sized particles. Gan and Qiao, (2011) investigated the burning characteristics of fuel droplets containing nano and micron sized aluminum (Al) particles by varying its size, surfactant concentration and type of base fluid. Tyagi et al. (2008) conducted a study to improve the ignition properties of diesel fuel and investigated the influence of size and quantity of Al and Al2O3 nanoparticles in a diesel fuel. It was inferred that it shortens the ignition delay and increased the ignition probability of fuel. Finally, it was concluded that, the increase in heat and mass transfer properties of the fuel has the potential of reducing the evaporation time of droplets. In the present investigation, the effect of mixture of ethanol with gasoline and carbon nanotubes on emission characteristics was evaluated using Jatropha biodiesel in a compression in a spark ignition engine. Materials and Methods In this study, a mixture of ethanol with gasoline (at five levels, 0, 10, 20, 30 and 40%) as a renewable fuel and carbon nanoparticles (at three levels of 0, 20 and 80 ppm) as catalyst were used in spark ignition engine (in 1000, 2000 and 3000 rpm). Engine pollutants such as sound, carbon monoxide, unburnt hydrocarbons, carbon dioxide and oxygen output were measured. Furthermore, a device was designed and manufactured to measure and display the amount of carbon monoxide in the exhaust outlet; moreover, if the amount of carbon increased air compressor was activated to reduce carbon monoxide in the exhaust outlet. Results and Discussion The results showed that with increasing ethanol consumption, the amount of carbon monoxide and unburned hydrocarbons were reduced. Furthermore, the amount of produced oxygen and carbon dioxide increased. Also adding carbon nanoparticles to fuel caused the engine sound level decreased. According to the observation, carbon monoxide decreased while using an electronic device compare to the engine without a carbon monoxide controlling system. This depicts that implementation of carbon monoxide can be control and reduce which is very useful while engine is working under the close environments. Conclusions The use of alternative fuel, gasoline as well as the reduction of exhaust emissions in the spark ignition engine is of great importance. Therefore, in the present study five levels of ethanol (0, 10, 20, 30 and 40%) and three levels of carbon nanoparticles (0, 20 and 80 ppm) were mixed with gasoline and used in spark ignition engine at three rotation speed (in 1000, 2000 and 3000 rpm). According to the results, there is a reduction in carbon monoxide and unburned hydrocarbons and increasing carbon dioxide emission by using ethanol, because of its fuel bound O2. Furthermore, 3.8% dB 54% reduction in sound and CO, respectively at 3000 rpm with E10 were observed.

In this paper, a new model has been proposed to estimate the electrical conductivity of polymer carbon nanotube (CNT) nanocomposites based on the conventional power-law model and Halpin-Tsai formulation. Halpin-Tsai model was originally presented to calculate the tensile modulus of composites, which can be modified for the estimation of the electrical conductivity by replacing the electrical parameters. The nature of the “b” exponent in the power-law model is defined according to CNT dimensions, CNT electrical conductivity, and the interphase thickness, and also the impacts of these parameters on the “b” and the electrical conductivity of nanocomposite are taken into consideration. The developed model interprets that the electrical conductivity of polymer-CNT nanocomposite increases as the concentration, length, and electrical conductivity of CNT and the interphase thickness increase. Furthermore, reduction in CNT diameter and waviness results in the growth of nanocomposite electrical conductivity. In order to validate the developed model, nanocomposite samples with different volume fractions were produced by the solid -state technique of the melt -blending method. The results of calculations and experimental procedures show good agreement. [ABSTRACT FROM AUTHOR]

In our previous work [1], pristine and functionalized carbon nanotubes with 1, 2 and 4 hours refluxing times and concentrations of 0.1, 0.25 and 0.5 Vol% were used to prepare nanofluids and their thermal conductivity was measured at 20, 30, 40 and 50 °C. Lots of empirical works cannot be done because they are time consuming and costly. One of the best methods for investigation of low cost and wide range of empirical works is using the modeling methods. The artificial neural network model is a method which replicates the initial sensory processes of the brain. It is possible to design a virtual laboratory using artificial neural networks to predict the results for the same conditions even not measured experimentally. In this work, a multilayer perceptron (MLP) neural network was used to design a virtual lab and modeling the experimental data including the thermal conductivity of ethylene glycol nanofluids containing CNTs. In order to achieve a minimum error, neural networks with different hidden layers (1, 2 and 3 layers) and different number of neurons in each layer (2, 3, 4, 5, 6, 10 and 15 neurons) were studied. The minimum error of 6.5% was obtained for the neural network with two hidden layers by 3 neurons in the first layer and 2 neurons in the second one. This network was used to predict the results in the conditions which were closed to experimental conditions and it was observed that the predicted results were in good agreement with the experimental results.

Carbon nanotubes contain impurities and deamorphization is one of the methods of their purification. In this study, for the first time, a solution of piranha with a ratio of 3:1 (30 ml sulfuric acid + 10 ml hydrogen peroxide) as well as microwave irradiation with processing time of 30 minutes were used to remove amorphous carbon from the nanotube arrays. Ultrasonication was performed to disperse pristine and purified carbon nanotubes in water and centrifugation was performed to separate large particles. To assess the removal of amorphous carbon, new characterization methods such as dispersed percent and floating percent were used. It was observed that with increase in the ultrasonication time (from 0 to 50 minutes), the dispersed percentage of treated arrays was increased (about 47%), while the floating percentage of pure array decreased (about 20%). These results are ascribed to the removal of amorphous carbon. The results of the thermo gravimetric analysis (TGA) were in good agreement with the results obtained from the newly proposed characterization methods. [ABSTRACT FROM AUTHOR]

Background and Aim: The residuals of drug are belonging to emerging pollutants. Drugs and their metabolites should be removed from water resources due to potential risks and their toxicities for humans and the environment.These materials are not completely eliminated by the conventional methods of water and wastewater treatment. The purpose of this study was to investigate the removal of acetaminophen using single-walled and multi-walled carbon nanotubes from aqueous environments. Materials and Methods: In this experimental study, the effect of different parameters such as: pH, initial concentration of acetaminophen, adsorbent dose, time of touch and mixing speed were investigated in acetaminophen removal by single-wall and multi-wall carbon nanotubes. The adsorption isotherms of Langmuir, Freundlich, Temkin, Dubinin-Rudeshkuvich and BET and pseudo-first and pseudo-second order adsorption kinetics were also investigated. Acetaminophen concentration was measured by spectrophotometer at (λ max=258 nm). Results: The result of the experiments showed that single-wall and multi-wall carbone nanotubes could be able to removal 38.59% and 28.24% of acetaminophen at time=45 min , PH=7. With increasing the dose of nanotubes, the removal percentage increased and absorption capacity decreased, Absorption process showed the highest correlation with Langmuir model and pseudo-second kinetics (R2>0.99). Conclusion: The results showed that single-walled and multi-walled carbon nanotube adsorbents can be used as an effective adsorbent in the removal of acetaminophen from aqueous environments along with other treatment methods.

An experimental study is presented on the critical buckling load of aluminum columns reinforced with glass/epoxy composite belts containing carbon nanotubes (CNTs) in this paper. The columns with solid circular cross-section are subjected to axial pressure load. Aluminum column specimens are reinforced with glass/epoxy and CNT/glass/epoxy. CNTs with 0.25, 0.5, and 1 weight percent are dispersed into the epoxy resin. Three layers of composite belts are wrapped around the columns. Glass fibers are placed along the column axes in each layer. The columns are tested under fixed end boundary condition using Instron hydraulic universal testing machine. Pressure load with respect to the end shortening is plotted for each specimen. To achieve the average value of the critical buckling load, four specimens are examined for each composite belt material. Results show that when 0.5% CNT/glass/epoxy composite belt is used to reinforce the column, the critical buckling load of the column increases by 45% with respect to the column with glass/epoxy composite belt. The proper dispersion of CNTs into the matrix material along with appropriate adhesion between the nanocomposite belt and the aluminum column leads to the increase of buckling load. To validate the results, buckling analysis of aluminum column reinforced with glass/epoxy composite belt was done in Abaqus finite element software. Finite element simulation confirms the experimental results obtained. [ABSTRACT FROM AUTHOR]

Water desalination systems is among the methods used to produce potable water to be used for domestic, agricultural and industrial applications. Reverse osmosis is a common methods employed for desalination facilities, mainly because of its low energy consumption, and high efficiency for permeate production. The main aim of this research is to use nanocomposite containing carbon nanotubes to improve membrane wall performance. in addition, the increase in the flux as a result of decreased clogging surface on the membrane was also studied. To accomplish the objective of the study, the synthesized polyamid reverse osmosis nanocomposite membrane were used for purification of brackish water with the characteristic of having the electroconductivity of 4000 µs/cm. The modified raw-multi walled carbon nanotubes membrane was embedded through polymerization method in order to increase porosities and hydrophilicity. Analysis of Contact angle, SEM, FTIR and AFM were done for recognizing the compounds which were created on the surface of membranes and membranes hydrophilicity. Three sets of samples were prepared for testing in the membrane cell synthesis analysis. Water flux and rejection rates were assessed every 30 minutes. Results of this study showed that the membranes have soft hydrophil surfaces and by increasing nanocomposite concentrations with specified measure, the water flux increased up to 30.8 L/m2h which was noticeable compared to the simple polyamide membranes. Our results also showed that fouling reduced considerably and the clogging condition was reduced by nanocomposite membranes, and the rejection rate was higher than 97 percent for all synthesized membranes with pyrrol.

In this paper due to the abundant and also different applications of carbon nanotubes doped with boron, molecular vibrations related to boron element were identified and investigated in B-doped carbon nanotubes by experimental, computational and simulation ‎methods. In the experimental approach, Raman spectra of MWCNTs and B- doped MWCNTs were recorded and the Raman active modes assigned to the relevant specific vibrations. In the computational approach, the vibrational frequencies of C-C and C-B (pure carbon chains and doped with boron) oscillators were simulated using simple harmonic oscillator model and shift of vibrational frequencies toward lower wavenumbers was observed. Finally, by software simulation approach, vibrational frequencies of carbon-carbon and carbon-boron were investigated using the Gaussian software. The D- band intensity increased as the boron concentration reached to 3% while the center of the peak downshifted by 8 cm-1 (1336 cm-1 ® 1328 cm-1). Doping of carbon nanotubes with the boron concentration in the range of 4 to 10% upshifted the D- band central position by 18 cm-1 (1328 cm-1® 1346 cm-1). The ID-IG ratio (the intensity of the disorder D mode divided by the intensity of the graphite G mode) was increased by B-doping of carbon nanotubes (0.75®1.5). In conclusion, the results of the present article reveals that the intensity and frequency variations of D and G modes in the pure and the B doped MWCNT structures were approved with acceptable accuracy by the experimental, computational and simulation methods.

Hypothesis: Electrospinning of nanoparticles/polymer solutions offers the potential to achieve novel composite nanofibers in a variety of high performance applications. In this respect, the aspect ratio and purity of multi-walled carbon nanotubes (MWCNTs) were examined to study the morphological and electrical properties of the electrospun composite nanofibers. Methods: In the first step, MWCNTs samples were characterized using scanning electron microscopy (SEM) and Raman spectroscopy. Next, nanocomposite solutions containing MWCNTs were prepared by physical dispersion method in presence of a non-ionic surfactant. Finally, the prepared composite solutions were loaded to a glass syringe and connected to a DC power supply device. The electrospinning was performed by applying a high voltage of 15kV between the needle and the rotating collector. Findings: It is generally accepted that a combination of G-band intensity and G/D ratio is useful to evaluate the purity and crystallinity of MWCNTs. The morphological properties of the electrospun composite nanofibers showed their high dependency on carbon nanotubes dimensions, so that at higher aspect ratios the morphological properties generally improved. The morphological analysis of the composite nanofibers revealed that the deformation of the nanofibers increased with increasing MWCNTs diameter. Very smooth surfaces of the composite electrospun nanofibers even with 1 wt% MWCNT concentration were successfully achieved because of the high stability of MWCNT dispersions. The composite nanofibers with higher purity and aspect ratio presented better electrical conductivity. The electrical conductivity of electrospun composite nanofibers could be adjusted from ~10–8 S/cm (insulator) to ~10–3 S/cm (conductor) by different aspect ratios and purities of MWCNTs. MWCNTs with high aspect ratio and high purity offer a promising way to develop electrospun composite nanofibers with improved morphological and electrical properties.

Discharge of toxic metals such as cadmium (Cu), lead (Pb), and zinc (Zn) in the environment can impact the quality of air and water. High concentration of these toxic metals larger than the regulated concentration in the air and water can pose serious human health risks. The aim of this research was to investigate the removal of these heavy metals (Cd, Pb and Zn) from aqueous solutions by using a multi walled carbon nanotubes modified by chitosan as an absorbent agent. To perform the experimental study, nitrate salt of heavy metals solution prepared with distilled water was used. Factors examined for the removal efficiency of heavy metals in this study include pH, absorbent dose concentration, retention time, and the initial concentration of heavy metals. All analytical analyses were performed according to standard methods. Also, the infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) used for identification and modification of the absorbent. The results obtained from this study showed that an increase in pH, retention time and initial concentration of heavy metals, also increased the adsorption efficiency rate. The optimum heavy metals removal efficiency was about 75% and that occurred when pH =7, retention time =120 minutes and the initial concentration of heavy metals =20 mg/L. In addition, plot of Langmuir and Freundlich adsorption isotherms for heavy metals showed that the adsorption process mostly follows the Freundlich isotherm. The limited data obtained from this experimental sudy, it can be concluded that using carbon nanotubes modified with chitosan as an absorbant agent is an effective method for the removal of heavy metals (Cd, Pb, and Zn) from aqueous solutions.

Abstract Background and aim: Antibiotics are a category of organic pollutants that can cause serious environmental problems through their disposal and uncontrolled release to the environment. The purpose of this study was to investigate the removal of sulfadimethoxine from aqueous solutions using carbon nanotubes. Materials and Methods: The present work was an experimental study in which the effects of different parameters, such as PH, time, doses of carbon nanotubes, and different concentrations of sulfadimethoxine, on the removal of antibiotic from solutions were examined. All experiments were carried out in a 100-mL reactor at laboratory temperature (24 ± 2 ° C) using a magnetic stirrer at 350 rpm. Results: The results showed that the maximum removal efficiency (94.5%) was occurred at pH = 6, adsorbent dosage 0.04 g, contact time of 30 min, and initial concentration of 20 mg/L. The findings on the effect of pH showed that the adsorption capacity increases with increasing pH, and at pH = 6, it reaches its maximum and then decreases again. The extent of removal was increased by increasing the dose of carbon nanotubes and the optimum amount for initial concentration of 100 mg/L (50 mL) was 0.04 g. The amount of absorption increased with increasing contact time and the maximum absorption occurred when the contact time was 30 min. The sulfadimethoxine antibiotic isotherm followed the Langmuir isotherm model (R2 = 0.9800) and the pseudo-second-order kinetic model (R2 = 0.9937). Conclusion: The results showed that carbon nanotubes have a high potential for removal of sulfadimethoxine from aqueous solutions, due to its properties like its high surface area.

In the peresent work, tetrakis(p-aminophenyl)porphyrin manganese(III) chloride was attached through an amide bond on multi-wall carbon nanotubes and the prepared catalyst was characterized by different methods. After synthesis and characterization of this catalyst, its catalytic activity was investigated as heterogeneous catalyst in the oxidation of sulfides with sodium periodate. Different sulfides were converted efficiently to their corresponding sulfoxides and solfones by this catalytic system. The oxidation products were sulfone and sulfoxide which isolated and identified. The effect of reaction parameters such as catalyst amount and different solvents on the catalytic activity was also investigated. This catalyst was reused several times without significant loss of its catalytic activity.

Global warming and other adverse environmental effects of fossil fuels have forced humans to consider clean and renewable energy resources. In this context, hydrogen production from water splitting reaction is a key approach. In order to reduce required overpotential for water oxidation reaction, it is necessary to use low cost and earth abundant electrocatalysts like Co, Cu, Fe, Mn, Ni and Zn nanostructures. Herein, cobalt nanostructures on steel-mesh substrate were applied. Electrochemical method was used for growth of Co nanoflakes because of its simplicity and scalability for commercial approach. On the other hand, using carbonaceous support layers including nanomaterials such as graphene and carbon nanotubes, can reduce overpotential and increase efficiency of the electrocatalyst. According to the results, 40 wt% of graphene oxide and 60 wt% of carbon nanotubes in prepared carbon paste led to better growth for cobalt oxide nanoflakes. For the mentioned layer, cobalt was detected in metallic crystalline phase and the overpotential and electrical resistance measured 305 mV and 20 Ω, respectively.

Thermal fatigue is one of the most important issues in different engineering fields. The importance of this phenomenon is its application in aerospace industries and considerable effects on the material properties. In this research, the effect of thermal fatigue on the machining quality of polymeric CNT-reinforced composites is studied. To follow this aim, initially the composite specimens with eight layers in symmetrical and unsymmetrical layups are fabricated and subjected to thermal cycling. Then, two different machining processes including conventional drilling and ultrasonic vibration assisted drilling are carried out and the thermal fatigue effects are experimentally studied. Additionally, the effects of various parameters including “addition of multi wall carbon nanotube”, “machining process” and “layup method” on machining quality of composites under thermal fatigue condition is investigated in order to obtain the least delamination. The results indicated that addition of multi-walled carbon nanotubes enhances the machining quality up to 13%. It was also revealed that the implement of ultrasonic assisted drilling could reduce the delamination damage up to 10%. [ABSTRACT FROM AUTHOR]

In the present study, multilayer nanocomposites fabricated by accumulative roll bonding (ARB) process. Aluminum sheets, copper sheets (with 0.1 and 0.3mm thickness) and multiwall carbon nanotubes (MWCNTs) were used as experimental materials. The rolling process continued to five cycles. Then, microstructure, hardness, tensile strength and electrical conductivity of nanocomposites were investigated. Necking and fracturing recognized as mechanisms of copper layers distribution in the aluminum matrix. The bonding strength between layers increased with the number of cycles due to the improvement of MWCNTs distribution. The results show that the hardness of aluminum increased with increasing copper layer thickness and these increases were about 30 and 32% for composites without nano reinforcements and nanocomposites contain MWCNTs, respectively. The highest hardness (147HV), is related to the sample containing carbon nanotubes and 0.3mm copper sheet, after five rolling cycles (446% increase compared to aluminum sheets). The results confirm the positive effect of copper and the MWCNTs on the improvement of strength. The highest strength and elongation is observed in the aluminum-copper-MWCNTs nanocomposite after four cycles. The results also indicated that the addition of copper and MWCNTs can simultaneously increase the strength and electrical conductivity of the resulted composites. [ABSTRACT FROM AUTHOR]

In this research, aero-thermo-elastic stability of fibrous laminated plates subjected to supersonic airflow has been investigated. The experimental method was used to determine the effect of carbon nanotubes on the thermo-elastic properties of the composite matrix material. Young’s modulus and linear coefficient of thermal expansion of neat epoxy and carbon nanotube reinforced epoxy was determined using the tensile test and dilatometry method. The modified Halpin-Tsi micromechanical model was used to characterize the mechanical properties of the carbon nanotubes-fiber-epoxy laminated composites. A rectangular simply supported plate subjected to supersonic airflow was assumed. The governing equation of motion was extracted using the energy method and Hamilton’s principle. Linear piston theory was used to evaluate the aerodynamic pressure. Galerkin’s method was employed to solve the governing equation. The influence of adding carbon nanotubes in epoxy resin was illustrated when glass or carbon fibers were used as microscale reinforcements. Moreover, the effect of plate aspect ratio and temperature on the aeroelastic stability boundary was investigated. Results show that for the plates with high aspect ratio, adding carbon nanotubes into the epoxy resin has more effect on the aeroelastic stability boundary especially when the glass fibers are used. According to the results, in high temperatures, carbon nanotubes have less effect on the expanding of the stability region. [ABSTRACT FROM AUTHOR]

Abstract Background: Nowadays, drug resistances are the main problems in no response of cancer patients to drug. Identification of molecular mechanisms and causative agents of drug resistance can be important to determine the treatment method in different stages of disease. In this study, for the first time, expression of multidrug resistance (MDR1) gene was studied in colorectal cancer by Carbon Nanotubes (CNTs)-based nanobiosensor method. Materials and Methods: At first, a nanobiosensor was designed based on carbon nanotubes (CNTs). After optimizing reaction condition to identify target DNA sequence, colorectal cancer patient’s cDNA samples were evaluated by nanbiosensor. Results: After immobilizing the probe on CNTs, Fluorescence immersion was quenched but by adding complementary DNA, fluorescence again was observed. In hybridization reaction of cDNA with nanobiosensor high significant levels of fluorescence emission was observed in colorectal cancer tumor samples compared normal tissue indicating high level expression of MDR1gene in tumor tissue. Conclusion: Finally, the evaluation of the expression of MDR1 gene by nanobiosensor indicated that in colorectal cancer tissue MDR1, mRNA level was higher than normal tissue. In addition, the results of this study indicated that carbon nanotubes-based nanobiosensor beside PCR-based method can be used as a very powerful tool for expression studies in human cancers at mRNA levels.

In this study, nonlinear axisymmetric bending analysis of Functionally Graded Carbon Nanotube Reinforced Composite (FG-CNTRC) cylindrical shell is investigated. Four distribution types of carbon nanotubes along the thickness direction of shells are considered, including a uniform and three kinds of functionally graded distributions. The material properties of FG-CNTRC shells are determined according to the modified rule of mixture. The equilibrium equations are derived based on First-order Shear Deformation Shell Theory (FSDT) and nonlinear Donnell strains. The coupled nonlinear governing equations are solved by Dynamic Relaxation (DR) method combined with central finite difference technique for different combinations of simply supported and clamped boundary conditions. For this purpose, a FORTRAN computer program is provided to generate the numerical results. In order to verify the accuracy of the formulation and present method, the results are compared with those available in the literatures for ABAQUS finite element package, as well as a similar report for an isotropic function shell. The appropriate accordance of the results indicated the accuracy of employed numerical solution in the present study. Finally, a parametric study is carried out to study the effects of distribution of carbon nanotubes (CNTs), shell radius and width-to-thickness ratios, boundary conditions and volume fraction of CNTs on the deflection, stress and moment resultants in detail. The results show that with increase of CNTS volume fractions, the O and UD distributions have the most and the least decrease of deflection, respectively, in both clamped and simply supported boundary conditions.

In this paper, chirality effect on the buckling behavior of SWCNTs has been investigated. In order to explore the effect of chiral angle, all structures are used with the same length and diameter but different chiral angles. For modeling of chemical bonds between carbon atoms, potential energy of molecular mechanics theory and strain energies of a 3D beam element have been equalized. After calculating the element properties, the node coordinates have been determined using a computer code developed in MATLAB software. Then, ANSYS software is used to study the chirality effects on axial and torsional buckling load. Results show that the chiral angle has no significant influence on critical axial force. However, chiral angle is an effective parameter in torsional buckling. Chiral angle of 19.11 degree has the maximum critical torsional moment among all structures. In counter-clock-wise loading condition, chiral angle of 9.64 degree has the minimum critical torsional moment. Also, the direction of twisting (cw or ccw) is important and the difference between cw and ccw critical torsional moment reaches its maximum value for chiral angle of 15.48 degree.

Today, electron therapy has a lot of advantages such as: its homogenous, dose in the target volume, low absorbed dose for the normal tissues, non-effective transmitted dose of air bubble which surrounded the target (in comparison of photon treatments), controllability in turning on and electron beam flux adjustment during the treatment. It has no interchangeable case in the most treatment centers. Electron can use for up to 20cm depth in radiation therapies. In this study, we demonstrate, for the first time, a design of flexible guider for the electron accelerator output, which may increase the treatment ability effectively. One of the important of its advantages is non-limited ability in treatment of tumors in case of deep depth, in other words overcome to limitation of surface cancer treatment and providing a safe condition for other normal tissues during the radiation therapy. One of the important of its advantages is non-limited ability in treatment of tumors in case of deep depth, in other words overcome to limitation of surface cancer treatment and providing a safe condition for other normal tissues during the radiation therapy. in other words overcome to limitation of surface cancer treatment and providing a safe condition for other normal tissues during the radiation therapy.

In this work, the optical properties dependence of Multi-Walled Carbon Nanotubes (MWNT) on concentration was discussed. MWNT samples were prepared in polypyrrole by an electrochemical polymerization of monomers, in the presence of different concentrations of MWNTs, using Sodium Dodecyl-Benzen-Sulfonate (SDBS) as surfactant at room temperature. The nonlinear refractive and nonlinear absorbtion indices were measured using a low power CW laser beam operated at 532 nm using z-scan method. The results show that nonlinear refractive and nonlinear absorbtion indices tend to be increased with increasing the concentration of carbon nanotubes. Optical properties of carbone nanotubes indicate that they are good candidates for nonlinear optical devices

In this study, Circular Disk Model (CDM) has been developed to determine the residual stresses in twophase and three- phase unit cell. The two-phase unit cell is consisting of carbon fiber and matrix. The three-phase unit cell is consisting of carbon fiber, carbon nanotubes and matrix in which the carbon fiber is reinforced with the carbon nanotube using electrophoresis method. For different volume fractions of carbon nanotubes, thermal properties of the carbon fiber and carbon nanotube in different linear and lateral directions and also different placement conditions of carbon nanotubes have been considered. Also, residual stresses distribution in two and three phases has been studied, separately. Results of micromechanical analysis of residual stresses obtained from Finite Element Method and CDM, confirms the evaluation and development of three dimensional CDM.

A well healthy environment can quietly affect the life quality and human community. In recent decades the need for and utilizing fossil had increased and thus the environmental pollutions including for soil has also increased. Petroleum contaminated soils are not suitable for agricultural, residential and social usage and cause economical, ecological and agricultural damage. To cope with this challenge, the use of additives such as carbon nanotubes has expanded to soil, but the use of these elements has raised concerns about their risk to biological processes and systems, such as effects on physiology and plant growth, and there have not been much studies on this issue. In order to investigate the interaction of soil petroleum pollution and carbon nanotubes on some plant characteristics such as wet mass, dry matter and plant length, seed and maize seedling were separately treated with 0, 10, 20 and 40 mg/l carbon nanotubes at the beginning. In pots containing soil with three levels of petroleum pollution, 2.43, 2.76 and 4.16% were cultivated with 3 replications. A completely randomized design was used in the form of factorial experiments. Wet mass, dry matter and length of shoot and root of plants were determined. The results showed that petroleum pollution had a negative effect on the growth characteristics. It was also observed that application of carbon nanotubes to maize (whether seed or seedling) depending on the concentration of these materials, could have different effects on plant growth parameters. [ABSTRACT FROM AUTHOR]

Background and Aim: The residuals of drug are belonging to emerging pollutants. Drugs and their metabolites should be removed from water resources due to potential risks and their toxicities for humans and the environment.These materials are not completely eliminated by the conventional methods of water and wastewater treatment. The purpose of this study was to investigate the removal of acetaminophen using single-walled and multi-walled carbon nanotubes from aqueous environments. Materials and Methods: In this experimental study, the effect of different parameters such as: pH, initial concentration of acetaminophen, adsorbent dose, time of touch and mixing speed were investigated in acetaminophen removal by single-wall and multi-wall carbon nanotubes. The adsorption isotherms of Langmuir, Freundlich, Temkin, Dubinin-Rudeshkuvich and BET and pseudo-first and pseudo-second order adsorption kinetics were also investigated. Acetaminophen concentration was measured by spectrophotometer at (λ max = 258 nm). Results: The result of the experiments showed that single-wall and multi-wall carbone nanotubes could be able to removal 38.59% and 28.24% of acetaminophen at time=45 min , PH=7. With increasing the dose of nanotubes, the removal percentage increased and absorption capacity decreased, Absorption process showed the highest correlation with Langmuir model and pseudo-second kinetics (R2>0.99). Conclusion: The results showed that single-walled and multi-walled carbon nanotube adsorbents can be used as an effective adsorbent in the removal of acetaminophen from aqueous environments along with other treatment methods. [ABSTRACT FROM AUTHOR]

Carbon nanotubes have special importance due to unique properties as an amplifier phase. In this paper, the effect of multiwall carbon nanotubes on water absorption and fatigue life of poly methyl methacrylate is investigated. To this end, nanocomposites based on polymethyl methacrylate, containing 0-1.5 weight percentage of multiwall carbon nanotubes are produced with screw and injection molding process. The morphology was studied, using scanning electron microscopy. Microscopic images examination showed that carbon nanotubes have been well released in the field of polymer. The fatigue testing of each of the prototypes was carried out under identical conditions. Based on the results of fatigue test, nanocomposite fatigue strength containing 0.5% carbon nanotubes increased than base polymer. Also, based on the results of water absorption test, the existence of multiwall carbon nanotubes in polymer field decreased absorption water of the samples. [ABSTRACT FROM AUTHOR]

Critical force and time are the two important output parameters in nanomanipulation of different particles. Various input parameters affect the critical force and time, among which dimensional parameters and velocity can be considered the most important ones. To accurately calculate the critical forces and time of the manipulation requires careful analysis of the effect of various input parameters. One of the new methods in affecting the sensitivity analysis of input parameters on problems are statistical sensitivity analysis methods, one of the most accurate methods of which is the Sobol method. Previously, research on the influence of various parameters on the 2D manipulation has been done. In this paper, for the first time, using Sobol statistical sensitivity analysis method, effects of various dimensional parameters, including length of cantilever, width of cantilever, thickness of cantilever, height of tip, the speed in direction of the x and y-axes, radius of the particle, radius of the tip needle, and length of particle have been studied on 8 output parameters, including critical force of sliding along the x-axis, rolling around the x-axis, sliding along the y-axis, rolling around the y-axis, and critical time of sliding along the x-axis, rolling around the x-axis, sliding along the y-axis, and rolling around the y-axis in 3D manipulation. The final obtained results demonstrate that “cantilever thickness” and “cantilever length” are the most influential parameters on critical forces, and “tip height” and “cantilever thickness” are the most influential ones on critical times. [ABSTRACT FROM AUTHOR]

Prevention, recognize and treatment of cancer is one target and concern in medical science. Novel drug delivery systems have been provided In order to improve the treatment of cancer. In these systems, specified amount of the drug with an appropriate carrier is forwarded inside the cell. Nanotubes can be used as a carrier for drug delivery due to the large empty space inside nanotubes for encapsulation the drug. With regard to the importance of drug delivery in cancer therapy, In this paper two types of Armchair(10 ,10) and Zigzag (18 ,0) single-walled carbon nanotubes and the method of encapsulation the Gemcitabine anti-cancer drug were checked out. The drug is stable energetically in both nanotubes due to the energy absorption of the drug in nanotubes. According to achieved Center of mass (COM) and Root-mean-square displacement (RMSD) diagrams, Zigzag carbon nanotube can be a suitable carrier to encapsulate the Gemcitabine anti-cancer drug.

In this paper, buckling behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates is studied in line with the plates thikness. All governing equations are presented incrementally, based on a First-order Shear Deformation Theory (FSDT) of plates and von Karman strain field. In order to find the critical buckling load, the axial load is applied to the plate incrementally and the equilibrium equations are solved by Dynamic Relaxation (DR) method. Parametric study of the effects of volume fraction of Carbon Nanotubes (CNTs), CNTs distribution, plate width-to-thickness ratio and aspect ratio of nano composite plates is done in detail. The results show that functionally graded distribution of CNTs causes a significant increase of critical buckling load.

In this study, a three-dimensional finite element (FE) model for armchair, zigzag and chiral single-walled carbon nanotubes (SWCNTs) is proposed. To create the FE models, nodes are placed at the locations of carbon atoms and the bonds between them are modeled using three-dimensional elastic beam elements. The FE model is used to investigate the influence of chirality and Stone-Wales defects on the ultimate strength (Ultimate stress and ultimate strain) of SWCNTs. Results indicate that Stone-Wales defect significantly reduces the ultimate stress and strain of armchair CNTs. But this defect has a negligible effect on the ultimate strength of zigzag nanotubes. Based on the results, the crack growth path in zigzag and armchair nanotubes have 90 and 45 degree angle to the long axis of the nanotube, respectively.

Background and Objective: Natural organic matters (NOMs) are a mixture of chemically complex polyelectrolytes with varying molecular weights, produced mainly from the decomposition of plants and animal residues. Various purification methods are used for removal of NOMs from water. The objective of this study was to remove NOMs from aqueous solution using reformed continuous carbon nanotubes column. Materials and Methods: The removal of NOMs from aqueous solution using reformed continuous carbon nanotubes column was studied. Effect of several variables such as zero point of pH (pHZPC), pH, influent concentration of natural organic matters were studied and different isotherms were assessed. Results: Investigation of pH effect showed that the adsorbability of NOMs increased with decreasing of pH. The experiments indicated that carbon nanotubes (CNT) samples exhibit pHZPC around 6. Results from Freundlich, Langmuir, and BET isotherm experiments revealed that the correlation coefficient R2 in Freundlich model was higher than that of Langmuir. In addition, experiments of continuous flow in different initial concentrations of NOMs showed that the adsorption capacities of CNT were 53.46, 30.40, and 24.75 mg/g for NOMs initial concentrations of 10, 5, and 3 mg/L, respectively. Conclusion: The present study shows that CNTs have high potential for adsorption of NOMs from aqueous solution

In this work we report the synthesis and characterization of hybrid nanostructures of multiwall carbon nanotubes (MWCNT) and cadmium sulphide (CdS) nanoparticles. In a solution of thioacetamide and cadmium sulphide, purified MWCNT are added to prepare the CNT/CdS hetrostructure. XRD diagrams, SEM images, and also photoluminescence spectra of the prepared samples are analyzed. SEM images show the CdS nanoparticles of 17nm size coated on the CNTs. Visible photoluminescence with peaks at 435 nm and 535 nm, obtained from the prepared CNT/CdS, is discussed. The synthesis technique can be simply extended to other luminescent dopants, and the possibility of making optoelectronic devises based on the CNTs is confirmed by this method

The carbon nanotube membranes which have unique properties can make dramatic changes in adsorption and separation of compounds. Adsorption of pollutants from uranium chemical processing units is one of the most important environmental issues in this industry. Therefore, the adsorption isotherms of UO2, F2, UF6, UF4 and UO2F2 into carbon nanotube were studied by using the Monte Carlo simulation in order to evaluate the performance of carbon nanotubes membranes in the uptake of compounds of uranium chemical processing units. Also in this study, the effects of pressure and diameter of the carbon nanotubes on the adsorption of compounds were investigated. The results indicate that the adsorption of compounds onto the carbon nanotubes is as follows: UO2 > UF4 > UO2F2 > UF6 > F2. In other words, the maximum and minimum adsorption onto the carbon nanotubes are related to UO2 and F2, respectively. The effects of pressure and diameter of the carbon nanotubes on the adsorption of compounds show that the adsorption isotherm of all gases increases with increasing pressure and diameter of the nanotubes and the pressure influence on the adsorption of the compounds depends on the type of component and the carbon nanotubes diameter.

Background: Nowadays, drug resistances are the main problems in no response of cancer patients to drug. Identification of molecular mechanisms and causative agents of drug resistance can be important to determine the treatment method in different stages of disease. In this study, for the first time, expression of multidrug resistance (MDR1) gene was studied in colorectal cancer by Carbon Nanotubes (CNTs)-based nanobiosensor method. Materials and Methods: At first, a nanobiosensor was designed based on carbon nanotubes (CNTs). After optimizing reaction condition to identify target DNA sequence, colorectal cancer patient's cDNA samples were evaluated by nanbiosensor. Results: After immobilizing the probe on CNTs, Fluorescence immersion was quenched but by adding complementary DNA, fluorescence again was observed. In hybridization reaction of cDNA with nanobiosensor high significant levels of fluorescence emission was observed in colorectal cancer tumor samples compared normal tissue indicating high level expression of MDR1gene in tumor tissue. Conclusion: Finally, the evaluation of the expression of MDR1 gene by nanobiosensor indicated that in colorectal cancer tissue MDR1, mRNA level was higher than normal tissue. In addition, the results of this study indicated that carbon nanotubes-based nanobiosensor beside PCR-based method can be used as a very powerful tool for expression studies in human cancers at mRNA levels. [ABSTRACT FROM AUTHOR]

The nanoscale fracture behavior of epoxy-based nanocomposites reinforced with double-walled carbon nanotube (DWNT) was investigated by molecular dynamics (MD) simulations technique. In order to prepare a nanocomposite model including polymer and DWNT, the exact atomic structure of epoxy was adopted as in previous experimental studies made by authors. Tersoff and Amber potential, which are well known potentials, were used for simulation of polymer and DWNT, respectively. Among different available methods to simulate the cross-linking process, a technique was adopted with closer similarity to what happens in real conditions. Therefore, when some especial atoms of monomer and hardener molecules were closer than a specific potential distance, the chemical bonds were created between them. To verify the prepared model, a pull-out simulation was carried out and the results were compared with those of previous studies. It was found that although a rather wide range for interface strength has been presented by different researchers and different techniques, the strength obtained in this study is in the middle of this range. In addition, the fracture energy obtained from the simulations for pure epoxy was compared with that of experimental results and good agreement was obtained. To evaluate the effect of nanocomposite structure at nanometer scale, DWNT was modeled in three different angles relative to the loading direction, including 0°, 45°and 90°. It was found that when DWNT is parallel with the loading direction (i.e. 90°) it has the least impact on the fracture energy. The maximum fracture energy was obtained when MWNT was at 45° relative to loading direction. These results were compared with the theories provided for conventional composites.

Organic and mineral compounds generated as products of waste mineralization within biological processes and accompanying physical and chemical processes are washed out by percolating rainwater through the deposit of wastes in landfill and form leachate that has created many health and environmental concerns.This study intended to determine the efficiency of reducing COD, BOD5, TS and color of Hamadan landfill leachate by using carbon nanotubes. Experiments were performed in batch reactor and changing effective factors such as pH, time and concentration of iron nanoparticles .The efficiency of carbon nanotubes were investigated using a statistical test, One-Way ANOVA software SPSS-12. Highest removal efficiency was at concentrations of 2500 mg/ L NZVI, pH = 2.5 and 10 minutes reaction time, 58.23%, 12.5%, 66.87% , 80% for COD, BOD, TS and color, respectively. The project results showed high potential for carbon nanotubes into absorbing organic use for treatment or pretreatment of Hamadan landfill leachate.