Nitrogen-Doped Carbon Nanotube/Polymer Nanocomposites Towards Thermoelectric Applications

This study investigates the impact of nitrogen doping on the performance of carbon nanotube (CNT)/polymer nanocomposites for thermoelectric applications; this was performed through measurement of conductivity of the generated nanocomposites. Three different catalysts (Co, Fe, and Ni) were used to synthesize nitrogen-doped CNTs (N-CNTs) by chemical vapor deposition technique. Synthesized N-CNTs were melt-mixed with a polyvinylidene fluoride (PVDF) matrix with a small-scale mixer at a broad range of loadings from 0.3 to 3.5 wt.% and then compression molded. Measurement of electrical conductivity of the generated nanocomposites showed superior properties in the following order of the synthesis catalyst: Co > Fe > Ni. We employed various characterization techniques to figure out the reasons behind dissimilar electrical conductivity of the generated nanocomposites, i.e., transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetric analysis, light microscopy, and rheometry. It was found out, that the superior electrical conductivity of (N-CNT)Co nanocomposites was due to a combination of high synthesis yield, high aspect ratio, low nitrogen content, and high crystallinity of N-CNTs coupled with a good state of N-CNT dispersion. Moreover, it was revealed, that nitrogen doping had an adverse impact on electrical conductivity and, thus, on thermoelectric performance of CNT/polymer nanocomposites

Analysis of stakeholder roles and the challenges of solar energy utilization in Iran

Growing energy demand, rising greenhouse gas emissions and the depletion of fossil fuels necessitates the development of renewable energy sources. In order to improve renewable energy utilization, it is necessary to determine the most important factors influencing energy strategy. The energy system of Iran is highly dependent on fossil fuels; however, Iran has a high potential for solar energy development and several policies are being pursued by the government to develop power generation by renewable energy resources. This study presents and discusses several important parameters of energy policy and security which make the installation of photovoltaic (PV) systems crucial for the future. Installation of solar PV will improve energy security, foster job creation and reduce environmental problems. It also introduces and investigates those institutions and organizations involved in developing renewable energies, especially solar energy. These include the Ministry of Energy and universities, both of which play key roles in the development of solar energy.fi=vertaisarvioitu|en=peerReviewed

Effects of Erbium Family Laser on Shear Bond Strength of Composite to Dentin After Internal Bleaching

Introduction: The aim of this study was to assess the effect of surface treatment with erbium: yttrium-aluminum-garnet (Er:YAG) and erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers on shear bond strength of composite resin to recently bleached dentin.Methods: In this study, 40 extracted human premolars were selected. The teeth were cut 4 mm apical to the cusp tip and were randomly divided into four groups (n = 10 in each group) for shear bond strength testing. For bleaching, 35% hydrogen peroxide (H2o2) gel (Opalescence Endo, Ultradent, South Jordan, UT, USA) was applied to dentin surfaces of all specimens for 10 days. Before etching and bonding, in Er,Cr:YSGG and Er:YAG laser groups, dentin surfaces were irradiated with Er,Cr:YSGG and Er:YAG lasers, respectively. In Er,Cr:YSGG group, Er:YAG group and control group, composite restoration was performed immediately after bleaching while in common procedure group, composite restoration was performed after seven days. The teeth were then subjected to shear bond strength testing machine. The data were statistically analyzed using analysis of variance (ANOVA) and Tukey test.Results: The mean and standard deviation (SD) of shear bond strength was 4.3 ± 1.4 MPa for control group, 6.7 ± 2.0 Mpa for Er,Cr:YSGG group, 14.4 ± 3.7 Mpa for Er:YAG group and 19.4 ± 2.6 Mpa for common procedure group.Conclusion: The shear strength of composite to Er:YAG laser-treated bleached dentin was significantly higher than control group while significantly lower than common procedure

Aromatic amino acids play a harmonizing role in prostate cancer: A metabolomics-based cross-sectional study

Background: Prostate cancer (PCa) is a common health problem worldwide. The rate of this disease is likely to grow by 2021. PCa is a heterogeneous disorder, and various biochemical factors contribute to the development of this disease. The metabolome is the complete set of metabolites in a cell or biological sample and represents the downstream end product of the omics. Hence, to model PCa by computational systems biology, a preliminary metabolomics-based study was used to compare the metabolome profile pattern between healthy and PCa men. Objective: This study was carried out to highlight energy metabolism modification and assist the prognosis and treatment of disease with unique biomarkers. Materials and Methods: In this cross-sectional research, 26 men diagnosed with stage-III PCa and 26 healthy men with normal PSA levels were enrolled. Urine was analyzed with proton nuclear magnetic resonance (1H-NMR) spectroscopy, accompanied by the MetaboAnalyst web-based platform tool for metabolomics data analysis. Partial least squares regression discriminant analysis was applied to clarify the separation between the two groups. Outliers were documented and metabolites determined, followed by identifying biochemical pathways. Results: Our findings reveal that modifications in aromatic amino acid metabolism and some of their metabolites have a high potential for use as urinary PCa biomarkers. Tryptophan metabolism (p < 0.001), tyrosine metabolism (p < 0.001), phenylalanine, tyrosine and tryptophan biosynthesis (p < 0.001), phenylalanine metabolism (p = 0.01), ubiquinone and other terpenoid-quinone biosynthesis (p = 0.19), nitrogen metabolism (p = 0.21), and thiamine metabolism (p = 0.41) with Q2 (0.198) and R2 (0.583) were significantly altered. Conclusion: The discriminated metabolites and their pathways play an essential role in PCa causes and harmony. Key words: Metabolomics, Prostate cancer, Aromatic amino acids, 1H-NMR spectroscopy

Providing a Distance Bounding Protocol Named Pasargad in order to Defend against Relay Attacks on RFID-Based Electronic Voting System

ABSTRACT The most important characteristic of RFID-base

A novel and cost-effective double-capsule nanocomposite coating based on carbon hollow spheres with self-healing performance for corrosion protection

The ability of a cost-effective self-healing nanocomposite system to restore its protection functionality in case of a coating defect is of pivotal importance to ensure durable performance under demanding corrosive conditions. In this research, a self-healing epoxy coating was fabricated by incorporation of carbon hollow spheres (CHSs) doped separately with epoxy and polyamine as film forming agents. Graphene-based CHSs were synthesized via silica templating method in presence of sucrose as a carbon precursor. After encapsulation of epoxy and polyamine agents in CHSs denoted as Ep-DCSs and Am-DCSs, respectively, 10 wt. % and 5 wt. % of Ep-DCSs and Am-DCSs were introduced in an epoxy matrix. The final nanocomposite coating was applied on the surface of mild steel substrates. A blank epoxy coating was also used as a control sample. The synthesized CHSs were characterized before and after the silica core removal using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The CHSs loaded with the film forming agents were evaluated using thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the protective and self-healing properties of the coatings were studied using electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET) and salt spray testing. The obtained results showed that the fabricated nanocomposite epoxy coating can heal appropriately the scratches applied on the surface of the coating barricading the accessibility of corrosive species to the metal substrate (Figure 1). Please click Additional Files below to see the full abstract

Impact of synthesis temperature on morphology, rheology and electromagnetic interference shielding of CVD-grown carbon nanotube/polyvinylidene fluoride nanocomposites

Employing chemical vapor deposition technique, multi-walled carbon nanotubes (CNTs) were synthesized over Fe catalyst at a broad range of temperatures, i.e. 550° C to 950° C (at 100° C intervals). CNTs were melt-mixed into a polyvinylidene fluoride (PVDF) matrix at various loadings, and then compression molded. Surprisingly, despite the ascending trend of CNT powder conductivity with the synthesis temperature, the nanocomposites made with CNT synthesized at 650° C had significantly lower percolation threshold (around 0.4 wt%) and higher electromagnetic interference shielding effectiveness (EMI SE) (20.3 dB over the X-band for 3.5 wt% CNT and 1.1 mm thickness) than the other temperatures. Exhaustive characterization studies were conducted on both CNTs and composites to unveil their morphological and electrical characteristics. Superior EMI shielding of CNT650° C was attributed to a combination of high carbon purity, aspect ratio, crystallinity, and moderate powder conductivity along with decent state of dispersion within the PVDF matrix

Evaluation of Efficacy of Low-Level Laser Therapy

Introduction: Given the inconsistencies in the literature regarding laser performance in non-surgical treatments, this study investigated the available literature to determine the advantages and disadvantages of low-power lasers in treating non-surgical complications and diseases.Methods: Authentic information from articles was extracted and evaluated to assess low-power laser performance for non-surgical treatments. A systematic search of studies on low-level laser therapy (LLLT) for non-surgical treatments was conducted mainly in PubMed and google scholar articles.Results: Four categories of diseases, including brain-related diseases, skin-related diseases, cancers, and bone-related disorders, which were treated by LLLT were identified and introduced. The various types of LLLT regarding the studied diseases were discussed.Conclusion: Positive aspects of LLLT versus a few disadvantages of its application imply more investigation to find better and efficient new methods

Tuneable Dielectric Properties Derived from Nitrogen-Doped Carbon Nanotubes in PVDF-Based Nanocomposites

Nitrogen-doped multiwall carbon nanotubes (N-MWNTs) with different structures were synthesized by employing chemical vapor deposition and changing the argon/ethane/nitrogen gas precursor ratio and synthesis time, and broadband dielectric properties of their poly(vinylidene fluoride) (PVDF)-based nanocomposites were investigated. The structure, morphology, and electrical conductivity of synthesized N-MWNTs were assessed via Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy, and powder conductivity techniques. The melt compounded PVDF nanocomposites manifested significantly high real part of the permittivity (ϵ′) along with low dissipation factor (tan δϵ) in 0.1 kHz to 1 MHz frequency range, suggesting use as efficient charge-storage materials. Longer synthesis time resulted in enhanced carbon purity as well as higher thermal stability, determined via TGA analysis. The inherent electrical conductivity of N-MWNTs scaled with the carbon purity. The charge-storage ability of the developed PVDF nanocomposites was commensurate with the amount of the nitrogen heteroatom (i.e., self-polarization), carbon purity, and inherent electrical conductivity of N-MWNTs and increased with better dispersion of N-MWNTs in PVDF

Depression among hemodialysis patients: a cross-sectional study in southeast of Iran

Background and aims: Mental disorders may negatively affect on the quality of life in hemodialysis patients and their response to treatment. The aim of present study was to examine the prevalence of depression and related risk factors in hemodialysis patients. Methods: In this cross-sectional study, during June 2013 to September 2013, 217 patients with hemodialysis whom were admitted to Kerman hemodialysis center were examined. The depression level of patients was assessed using Iranian version of Beck Depression Inventory. Results: The mean score of depression was 24.2±12.6 (range: from 2-59). Totally, 29, 30 and 27.4 were reported as suffering from mild, moderate and severe level of depression, respectively. The results of the present study also showed that diabetic patients and patients with hypertension were significantly at a higher risk of depression. Conclusion: Results of the present study indicates that depression is highly prevalent in hemodialysis patients. It is important that all patients with maintenance hemodialysis be frequently screened for signs and symptoms of psychiatric disorders such as depression