Search

In this work, we report a buckypaper composite with properties suitable for high performance electrodes of redox supercapacitors. The synthesis employs a specific combination of the double- and triple-walled carbon nanotubes (FWCNT) with cellulose nanofibrils (CNF), with dimensions of 20–50 nm in width and lengths of up to several hundred microns. The generated composite (BP/CNT@CNF) preserves the structure of the FWCNTs and ensures greater wettability, without significant damage to electrical conductivity. When compared to a buckypaper produced without CNF, BP/CNT@CNF is completely moldable and flexible, with an increase of about 375% in tensile strength, and 400% in the maximum strain. As electrodes, BP/CNT@CNF is stable in different aqueous redox electrolytes at different pHs containing hydroquinone (HQ in 1.0 M H2SO4), potassium hexacyanoferrate(II) (K₄[Fe(CN)₆] in 3.0 M KOH) and KBr in neutral medium. In all media, excellent capacitance retentions are obtained, evaluated in 12,000 cycles. The best electrochemical performances are obtained with HQ/H2SO4 as a redox electrolyte. High specific capacitance values are found from 1 A g−1 (380.8 F g−1) to 15 A g−1 (216.1 F g−1), with energy and power densities corresponding to 28.2 W h kg−1 and 3974.7 W kg−1, respectively, calculated at electrode level.

In this article, we explore electrical double-layer capacitors (EDLCs) based on ionic liquids (IL), focusing on their stability and efficiencies (Coulombic and energetic). We analyze the conventional voltammetric methods to determine the electrochemical stability window, pointing out that a simple analysis of Coulombic efficiency, under different current and voltage conditions in galvanostatic experiments, has the advantage of being more representative for real cells, especially when studied together with energy efficiency. In addition, we study how IL-based EDLCs differ from aqueous and organic ones in terms of energy efficiency correlating with the physicochemical properties of electrolytes. Finally, we discuss the high resistance of this type of EDLC that has a detrimental effect on energy efficiency and cycling performance, even when the Coulombic efficiency is close to 100%., The authors would like to thank the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)/Brazil for ́ the financial support (Process No. 458487/2014-7). The authors would like to acknowledge the Instituto Nacional de Ciencia e Tecnologia em Nanomateriais de Carbono (INCT ̂ Nanocarbono)/CNPq. R.L.L. is recipient of fellowship from CNPq (Grant No. 313304/2017 - 3). M.C.G.S. thankfully acknowledge the scholarship received from the Coordenaca̧ õ de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) - Brazil.

Scorpion venom is a rich source of biologically active components and various peptides with high-potential therapeutic use that have been characterized for their antimicrobial and antiproliferative activities. Stigmurin is a peptide identified from the Tityus stigmurus venom gland with high antibacterial and antiproliferative activities and low toxicity. Amino acid substitutions in peptides without a disulfide bridge sequence have been made with the aim of reducing their toxicity and increasing their biological activities. The purpose of this study was to evaluate the structural conformation and structural stability, as well as antimicrobial, antiproliferative, and hemolytic activities of two peptide analogs to Stigmurin, denominated StigA6 and StigA16. In silico analysis revealed the α-helix structure for both analog peptides, which was confirmed by circular dichroism. Data showed that the net charge and hydrophobic moment of the analog peptides were higher than those for Stigmurin, which can explain the increase in antimicrobial activity presented by them. Both analog peptides exhibited activity on cancerous cells similar to the native peptide; however, they were less toxic when tested on the normal cell line. These results reveal a potential biotechnological application of the analog peptides StigA6 and StigA16 as prototypes to new therapeutic agents. publishersversion published

A microwave-assisted functionalization of carbon nanotubes (CNTs) with isocyanate groups allowed a reduction of functionalization time from 24 h to 30 min with no change in the degree of functionalization or in the nanotube characteristics. Polymer nanocomposites with enhanced mechanical properties were obtained because of the tailored interface by the covalent linkage between the surface-modified multiwalled-carbon nanotubes (MWCNTs) and an elastomeric polyurethane (PUE) matrix. The mechanical data revealed that the composite containing 0.25 wt % of MWCNT-NCO showed an increase of 31% in tear strength and 28% in static toughness. A good adhesion between the matrix and individually dispersed nanotubes was observed in the scanning electron microscopy and transmission electron microscopy images. Nanoindentation and nanoscratch experiments were conducted to investigate the properties on the sub-surface. An increase by a factor of 3 in the scratch hardness was observed for the composite with 0.50 wt % of MWCNT-NCO with respect to the neat PUE. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44394.

Concrete bridge deck deterioration is a significant problem that must be addressed to preserve highway infrastructure investments in bridges around the world. Reducing the cost of bridge deck maintenance is critical to government and private agencies responsible for maintenance of bridges. Maintenance challenges increase as many bridges begin to approach the end of their design life and traffic loads continue to increase. One means of reducing the cost of bridge deck maintenance is to accurately evaluate the condition of the structure and its constituent materials. Current methods used to evaluate deterioration of bridge decks include acoustic, electrochemical, electromagnetic, and visual inspection techniques. The purpose of this study was to assess the advantages and limitations of three available evaluation methods. The evaluation techniques included in this study were ground penetrating radar, the chain drag method, and IE. These techniques represent an important group of inspection methods currently used to evaluate in-service bridge decks. The bridge deck used in the study contains significant delaminations but exhibits virtually no outwardly visible signs of these deficiencies, so a detailed visual inspection survey of the deck was not included. Cores were taken from the bridge deck at selected locations to confirm the accuracy of the results obtained through each evaluation method. This paper presents the findings from each method and describes their respective advantages and limitations.

This paper reports the development of superhydrophobic nanocomposite systems which are also oleophilic. As hydrophobicity is based on low energy surface and surface roughness, the electrospinning technique was selected as the manufacturing technique. N , N ′ dimethylformamide (DMF) was employed as the polystyrene (PS) solvent. The “Tea-bag” (T-B) nanocomposite system is based on exfoliated graphite surrounded by PS superhydrophobic membranes. The T-B systems were tested regarding its adsorption and absorption rates. To test these properties, it was employed three different water/oil emulsions, i.e., new and used motor oil, which have physical properties (viscosity and specific gravity) similar to heavy crude oil extracted in Brazil, and vacuum pump oil (which does not form oil/water emulsion). It was observed that oil adsorption rate is dependent on oil surface tension, while the absorption rate is mainly dependent on membrane/exfoliated graphite surface area. Experimental data show that oil absorption rates ranged between 2.5 g/g and 40 g/g, while the adsorption rate oscillated from 0.32 g/g/min to 0.80 g/g/min. Furthermore, T-B systems were tested as containment barriers and sorbent materials with good results including its recyclability.

A novel and simple method to prepare nickel-based catalysts for ethanol steam reforming is proposed. The present method was developed using castor oil as a precursor. The results clarify that the nickel–carbon (Ni/C) catalyst has a high activity for ethanol steam reforming. It was observed that the catalytic behavior could be modified according to the experimental conditions employed. Moreover, it is interesting to note that the increase in the catalytic activity of the Ni/C nanocomposite over time, at 500 and 600 °C of reaction temperature, may be associated with the formation of filamentous carbon. The preliminary results indicate that the novel methodology used, led to the obtainment of materials with important properties that can be extended to applications in different catalytic process.

This paper describes the design, construction and characterization of a subcarrier multiplexed broadband digital microwave radio link with Viterbi error control coding. The design and construction of the RF and microwave devices are described and analyzed. A key point of the research is that low cost materials could be used to implement a broadband wireless link. The effect of error control coding on the system is analyzed and bit error rate measurements were performed. Adjacent channel interference (ACI) measurements were also performed to assess the performance of the link in the presence of an adjacent carrier.

Aims: To assess whether feeding bioassays using culture-supernatant proteins could be combined with PCR into a first-tier screening strategy for Vip3A-like genes efficient against tropical Spodoptera frugiperda. Methods and Results: Out of 12 Bacillus thuringiensis strains studied, the total protein concentrated from the culture supernatant of only the strain HD125 yielded a significantly increased armyworm mortality and an intense band of the predicted size for VIP3A protein in SDS-PAGE. However, PCR and sequencing data indicated Vip-like genes are ubiquitous in tropical B. thuringiensis isolates. Interestingly, the HD125 strain was also the only one displaying a single-band amplification pattern and the highest sequence identity to the reported Vip3A(a) gene. Conclusions: Results suggest the insecticidal effectiveness of putative VIPs in B. thuringiensis isolates can be preliminarily estimated by the use of supernatant-derived total protein in feeding experiments, though only in a limited manner. Significance and Impact of the Study: A simple and cost-effective first-tier screening strategy for VIP-derived activities in B. thuringiensis collections can be developed by combining PCR and feeding bioassays. Moreover, the employed primers showed to be useful as a tool for strains differentiation at DNA level, and for characterization and isolation of Vip-like genes in tropical B. thuringiensis germplasm.

@Background: elevated heart rate preceding the onset of ventricular tachycardia (VT), suggesting an increased sympathetic tone, has been reported to reduce the success of antitachycardia pacing (ATP) therapy in patients with implantable cardioverter defibrillators (ICD). Based on the data of the Variability Learned from Implantable Defibrillators (VALID) study, we aimed to assess the impact of autonomic tone on ATP effectiveness in ICD recipiens. Methods and results: a total of 36 out of 226 VALID-study patients implanted with a Biotronik ICD(Phylax XM or Microphylax+) were considred for the present sub-study. These devices have extended memory capacities (18000 RR intervals) that offerred the ability of analyzing heart rate variability (HRV) before the begening of the arrythmia. All the patients had ischemic heart disease. ATP programming was standardized within VT zones. During follow-up, 106 VTs recurred in these patients, 95 were terminated by ATP (ATP+) and ATP was unseccessful in 11 VTs (ATP-). HRV parameters were analyzed during the 30 minutes preceding VT onset. Two time- and three frequency-domain indices were derived semi-automatically: the standard deviation of normal RR intervals (SDNN), the proportion of adjacent normal RR intervals differing by > 50 ms (pNN50), the low-frequency (LF) power reflecting sympathetic tone, the high-frequency (HF) power reflecting parasympathetic activity, and the LF/HF power ratio. The following table summarizes the main