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•Flexible graphene supercapacitors (SCs) were fabricated with porous oxides on their anodes.•The porous oxides Al2O3, Sr2CeO4, and ZnO enhanced the capacitance of the devices by 40–78 ...times.•The introduction of the porous oxides into the SCs stabilized their output voltage and favored a battery-like behavior.
This work reports the electrochemical performance of flexible graphene-based supercapacitors (SCs) fabricated with and without porous oxides of: Al2O3, Sr2CeO4 and ZnO. According to the scanning electron microscopy images, the Al2O3, Sr2CeO4, and ZnO have particle sizes of 20−40 μm, 0.4−5 μm, and 100−200 nm, respectively. In addition, the X-ray diffraction analysis revealed that Al2O3, Sr2CeO4 and ZnO have rhombohedral, orthorhombic, and wurtzite crystalline structures, respectively. The electrochemical performance of the SCs devices was also evaluated and we found that the SC devices made with Al2O3 (G/Al-SC device), Sr2CeO4 (G/Sr-SC device) and ZnO (G/Zn-Sc device) had 40.5, 67 and 78 times more capacitance than the SC device made without porous oxides. Additionally, the energy density of the devices increased in the order: G/Al-SC < G/Sr-SC < G/Zn-SC, in agreement with the order of increase of the surface area for the porous oxides according to the BET measurements: Al2O3 (65.06 m2 g−1)<Sr2CeO4 (214.7 m2 g−1)<ZnO (335.6 m2 g−1). Ce3+/Ce4+ species and carboxylic groups were detected by X-ray photoelectron spectroscopy and Fourier transform infrared techniques, respectively. The presence of such species and carboxylic groups was important because they worked as redox centers for the charge storage. Thus, the results presented here could be useful for the development of graphene-based batteries with high energy density and prolonged discharge times.
By means of a symbolic method, a new family of time-space harmonic polynomials with respect to Lévy processes is given. The coefficients of these polynomials involve a formal expression of Lévy ...processes by which many identities are stated. We show that this family includes classical families of polynomials such as Hermite polynomials. Poisson–Charlier polynomials result to be a linear combinations of these new polynomials, when they have the property to be time-space harmonic with respect to the compensated Poisson process. The more general class of Lévy–Sheffer polynomials is recovered as a linear combination of these new polynomials, when they are time-space harmonic with respect to Lévy processes of very general form. We show the role played by cumulants of Lévy processes, so that connections with boolean and free cumulants are also stated.
Diabetic ketoacidosis with mild hyperglycemia is a major complication of sodium-glucose cotransporter 2 inhibitors. Although its use is not approved for patients with type 1 diabetes mellitus, the ...drug is often prescribed with the hope of optimizing metabolic control. We report a 20 years old female with hypothyroidism and type 1 diabetes consulting for vomiting and abdominal pain. The patient had used canagliflozin during the two previous months. Laboratory showed a blood glucose of 200 mg/dl, a severe metabolic acidosis (pH 7.1) and ketonemia. The patient was successfully treated in the intensive care unit.
•Flexible graphene composites were used for smoke detection.•Ruddlesden Popper perovskite (RPP) microparticles were used as sensitizing material.•The smoke sensor operates with low power consumption ...(0.7–3.3 mW).•The smoke sensor has a fast response time of 1−2 s.
The fire risks detection using reliable devices with compact design and ultralow energy consumption has been an important topic of research in the last years. Therefore, this work reports the fabrication and electrical characterization of flexible graphene sensors (FGSs) for smoke detection. For this, a flexible graphene composite with thickness of 1.0 ± 0.1 mm was fabricated using a mold-casting method and sensitized with Ruddlesden Popper perovskite (RPP) and TiO2 micro/nanoparticles for smoke detection purposes. The electrical characterization indicates that the sensors sensitized with the RPP microparticles present faster response times and lower recovery times than those sensitized with TiO2 nanoparticles. The main advantages of these sensors are: 1) They operate with very low power consumption (2−7 mW), and 2) they do not need to be in direct contact with the smoke source or fire source as reported in previous graphene based sensors. Thus, the flexible smoke sensors presented here offer new opportunities to develop a new generation of low cost and compact sensors which can be re-designed in the near future for detecting other types of gases for security purposes or medical applications.
The thermoresistive behavior of multiwall carbon nanotube (MWCNT)/polysulfone composites is experimentally investigated under heating-cooling cycles. Composites with MWCNT weight concentrations ...between 0.5 and 50 wt.% were fabricated and their morphology and porosity were examined. Changes in their electrical resistance upon changes in temperature were simultaneously measured under heating-cooling cycles above and below room temperature (25 °C), and under incremental steps of constant temperature. The thermoresistive sensitivity (temperature coefficient of resistance, TCR) and the hysteresis of each heating-cooling cycle were also investigated. Composites with MWCNT concentrations of 25 wt.% and below showed a positive TCR, while negative ones were measured for composites with 40 wt.% and 50 wt.%. The thermoresistive hysteresis was higher for composites with high MWCNT content (40 wt.% and 50 wt.%). Higher TCRs were found for temperatures above room temperature than below, and dominance of the MWCNT inherent thermoresistivity was observed for composites with very high MWCNT content (≥40 wt.%). Finally, the potential of this material to perform as a thermistor was assessed by comparing its readings to those of a commercial (solid state) sensor, showing very high sensitivity, good reproducibility and fair agreement with the commercial sensor.
The aim of this work is to investigate the effect of the applied voltage on the morphological and mechanical properties of electrospun polycaprolactone (PCL) scaffolds for potential use in tissue ...engineering. The morphology of the scaffolds was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and the BET techniques for measuring the surface area and pore volume. Stress-strain curves from tensile tests were obtained for estimating the mechanical properties. Additional studies for detecting changes in the chemical structure of the electrospun PCL scaffolds by Fourier transform infrared were performed, while contact angle and X-ray diffraction analysis were realized for determining the wettability and crystallinity, respectively. The SEM, AFM and BET results demonstrate that the electrospun PCL fibers exhibit morphological changes with the applied voltage. By increasing the applied voltage (10 to 25 kV) a significate influence was observed on the fiber diameter, surface roughness, and pore volume. In addition, tensile strength, elongation, and elastic modulus increase with the applied voltage, the crystalline structure of the fibers remains constant, and the surface area and wetting of the scaffolds diminish. The morphological and mechanical properties show a clear correlation with the applied voltage and can be of great relevance for tissue engineering.
Introduction:
Patients with rheumatoid arthritis (RA) present a higher incidence and severity of periodontitis than the general population. Our study, Outcomes of Periodontal Treatment in Patients ...with Rheumatoid Arthritis (OPERA), was a randomized waiting-list controlled trial using mixed methods. Patients randomized to the intervention arm received intensive periodontal treatment, and those in the control arm received the same treatment with a 6-mo delay.
Aim:
The nested qualitative component aimed to explore patients’ experiences and priorities concerning oral health and barriers and facilitators for trial participation.
Methods:
Using purposive sampling until thematic saturation was reached, we conducted 21 one-to-one semistructured interviews with randomized patients in either of the 2 treatment arms as well as with patients who did not consent for trial participation.
Results:
The patients described their experiences about RA, oral health, and study participation. Previous experiences with dental care professionals shaped patients’ current perceptions about oral health and the place of oral health on their list of priorities compared with other conditions. Patients also highlighted some of the barriers and facilitators for study participation and for compliance with oral health maintenance. The patients, in the control arm, presented their views regarding the acceptable length of waiting time for the intervention.
Conclusion:
The associations between periodontal and systemic health are increasingly recognized by the literature. Our study provided an insight into RA patients’ experiences and perceptions about oral health. It also highlighted some of the barriers and facilitators for participating in a periodontal interventional study for this group. We hope that our findings will support the design of larger interventional periodontal studies in patients with RA. The complex challenges faced by the burden of RA and the associated multimorbidities in this patient group might highlight opportunities to improve access to oral health services in this patient population.
Knowledge Transfer Statement:
This article provided insights into the experiences and perceptions of rheumatoid arthritis patients about their oral health to improve patient participation in a definitive clinical trial.
A two-patch logistic metapopulation model is investigated both analytically and numerically focusing on the impact of dispersal on population dynamics. First, the dependence of the global dynamics on ...the stability type of the full extinction equilibrium point is tackled. Then, the behaviour of the total population with respect to the dispersal is studied analytically. Our findings demonstrate that diffusion plays a crucial role in the preservation of both subpopulations and the full metapopulation under the presence of stochastic perturbations. At low diffusion, the origin is a repulsor, causing the orbits to flow nearly parallel to the axes, risking stochastic extinctions. Higher diffusion turns the repeller into a saddle point. Orbits then quickly converge to the saddle’s unstable manifold, reducing extinction chances. This change in the vector field enhances metapopulation robustness. On the other hand, the well-known fact that asymmetric conditions on the patches is beneficial for the total population is further investigated. This phenomenon has been studied in previous works for large enough or small enough values of the dispersal. In this work, we complete the theory for all values of the dispersal. In particular, we derive analytically a formula for the optimal value of the dispersal that maximizes the total population.
A dumbbell‐shaped dialkylammonium ion (see scheme) templates the formation, about its NH2+ center, of a crown ether like macrocycle under thermodynamic control from dialdehyde and diamine precursors. ...The imine‐containing 2rotaxane that ensues was converted by reduction into a kinetically stable interlocked molecule, which has been characterized in the solid state by X‐ray crystallography in both free base and salt forms.
This work reports the electrochemical properties of graphene supercapacitors that employ flexible graphene electrodes (FGEs) coated by V2O5 (VOx) or carbon nanotubes (CNTs)/VOx layers. According to ...scanning electron microscopy images, the morphology of VOx consists in micro-ribbons with lengths of 20–45 μm and widths from 5 to 12 μm. The CNTs form interconnected long fibers, which were functionalized with carboxylic groups for producing defects. We demonstrated that the gel electrolyte used for the supercapacitors produces V4+-oxygen vacancies (VO) defects. Both, the CNTs and V4+-VO defects act as redox centers, which delay the current discharge in the supercapacitors. The presence of the carboxylic groups, defects in CNTs, defects in VOx, and oxidation states (V4+ and V5+), were confirmed by the UV–Vis, XPS, and FTIR techniques. The electrochemical characterization of the supercapacitors indicated that the devices made with FGEs coated by VOx or CNTs/VOx layers produced constant voltages of 0.14 V and 0.38 V during 535 and 593 min, respectively. The increase of voltage is explained by the increase of surface area and by the extra redox centers (defects) introduced by the CNTs. The results indicated that the CNTs/VOx layer increases the voltage and discharge times of the graphene supercapacitors, which can be of interest for the development of graphene systems with high charge storage capabilities.
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•Flexible Supercapacitors (SCs) were made with graphene electrodes.•The SCs with CNTs and V4+-VO defects in their electrodes had prolonged discharge times.•A maximum constant voltage discharge of 0.38 V was observed for 10 h.
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