This work studies the structural, microstructural, and magnetic properties of carbon nanotubes with magnetic iron carbide nanoparticles attached to their walls. The samples were fabricated in a ...single step using a modified chemical vapor deposition (CVD) method. The proposed method allows to obtain carbon nanotubes with iron carbide nanoparticles partially immersed in their walls. The carbon nanotubes were characterized using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM). Results show that the obtained carbon nanotubes are multi-walled with a bamboo-like structure. They have an average diameter of 40 nm and inner cavities of 20 nm in diameter. The magnetic nanoparticles are firmly fixed to the nanotubes, and they have an average diameter of 15 nm with rounded borders. The iron carbide nanoparticles exhibit a ferromagnetic behavior with high magnetic saturation resulting from their morphological characteristics and their location on the walls of the nanotubes, which prevent their agglomeration and reduce dipolar interactions.
In this work, the remanence properties and the hyperfine parameters of the strontium hexaferrite were investigated when a copper layer was deposited on its surface using magnetron sputtering. The ...magnetic properties and maximum energy product were significantly improved after the copper was deposited on the hexaferrite. The magnetic interactions were studied using IRM and DCD remanent magnetization processes and by the construction of the Henkel plots and the
δM
curves which allowed us to assess the effect of copper on the observed enhancement of the magnetic properties. X-ray diffraction confirms the copper deposition while scanning electron microscopy shows a homogeneous deposited layer. The Mössbauer spectroscopy was used to analyze the effect of copper on the hyperfine parameters of the iron nuclei. Results showed a competition between the magnetizing-like and the demagnetizing-like interactions in the uncoated hexaferrite. However, the strength of the demagnetization-like interaction is significantly weakened because of the copper layer deposited on the hexaferrite surface. This behavior suggests the emergence of a magnetic coupling with a magnetizing effect. In addition, the Mössbauer analysis revealed that copper increased the hyperfine fields and strongly affected the electronic cloud of the 4f
I
and 2a iron sites.
Abstract
In this work, strontium hexaferrite (SrFe
12
O
19
) was prepared using two different methods, the solid-state reaction and the sol–gel pechini methods. In each case, the structural ...properties and microstructural features were analyzed in order to evaluate their influence on the photocatalytic activity of the strontium hexaferrite. In addition, the magnetic properties of each sample were also investigated. The analysis of the photocatalytic activity was done using methylene blue as a test dye. The results show that the fabrication method significantly impacts how the photocatalytic activity occurs. Firstly, the bandgap energy of the sample obtained by the solid-state reaction method turned out to be smaller than that obtained by the sol–gel pechini method. This behavior was attributed to the structural differences shown between the two samples. On the other hand, particle size also has a significant effect on photochemical reactions. However, smaller particle sizes make it difficult for photons to transport in the system, resulting in reduced photocatalytic activity. In this case, better results were obtained from the sample obtained from the solid-state reaction method.
At present, it is unknown whether the use of nutrient-rich dairy proteins improves the markers of sarcopenia syndrome. Therefore, our proposal was to investigate whether adding 210 g of ricotta ...cheese daily would improve skeletal muscle mass, handgrip strength, and physical performance in non-sarcopenic older subjects.
This was a single-blind randomized clinical trial that included two homogeneous, randomized groups of men and women over 60 years of age. Participants in the intervention group were asked to consume their habitual diet but add 210 g of ricotta cheese (IG/HD + RCH), while the control group was instructed to consume only their habitual diet (CG/HD). Basal and 12-week follow-up measurements included appendicular skeletal muscle mass (ASMM) by dual-energy X-ray absorptiometry, handgrip strength by a handheld dynamometer, and physical performance using the short physical performance battery (SPPB) and the stair-climb power test (SCPT). The main outcomes were relative changes in ASMM, strength, SPPB, and SCPT.
ASMM increased in the IG/HD + RCH (0.6±3.5 kg), but decreased in the CG/HD (-1.0±2.6). The relative change between groups was statistically significant (P=0.009). The relative change in strength in both groups was negative, but the loss of muscle strength was more pronounced in CG/HD, though in this regard statistical analysis found only a tendency (P=0.07). The relative change in the balance-test scores was positive for the IG/HD + RCH, while in the CG/HD it was negative, as those individuals had poorer balance. In this case, the relative change between groups did reach statistical significance.
The addition of 210 g of ricotta cheese improves ASMM and balance-test scores, while attenuating the loss of muscle strength. These results suggest that adding ricotta cheese to the habitual diet is a promising dietetic strategy that may improve the markers of sarcopenia in subjects without a pronounced loss of ASMM or sarcopenia.
•Aluminum deposition with magnetron sputtering on strontium hexaferrite.•Deposited aluminum improves the maximum energy product of Sr-hexaferrite.•Remanence properties of the strontium hexaferrite ...with deposited aluminum.•Aluminum deposit on the Sr-hexaferrite reduces the demagnetizing-like interactions.
This work deals with the effect that aluminum deposited on the strontium hexaferrite has on the magnetic and remanence properties. The aluminum was deposited using magnetron sputtering and the deposit thickness was varied through two deposition times. The presence of the aluminum was corroborated by X-ray diffraction and scanning electron microscopy. The magnetic characterization showed an increment in remanence squareness (Mr/Ms), while the maximum energy product (BHmax) exhibited a large increment regarding the hexaferrite without aluminum. Isothermal remanent magnetization (IRM) and direct current demagnetization (DCD) curves were measured for two samples with different amounts of deposited aluminum and for the strontium hexaferrite without aluminum. The Henkel plots and δM curves were discussed in the Stoner-Wohlfarth framework. Results show a diminishing of demagnetizing-like interactions as the deposited aluminum increases on the hexaferrite surface. This behavior suggests that aluminum promotes the emergence of a type of exchange interaction with a magnetizing effect.
In this study the pressure distribution homogeneity on the catalytic surface is found to provide a simple and reliable fuel flow parameter that can be used to optimize the bipolar plate geometry and ...the PEM fuel cell performance. Finite element commercial ANSYS software was used to determine the fuel velocity, pressure and mass distribution on eight different bipolar plate geometries. These geometries were also fabricated and characterized experimentally in order to establish a correlation between the power densities with the fuel flow parameters obtained from the simulations. The results show that a highly uniform pressure distribution of the fuel in the bipolar plate is necessary to obtain higher power densities. Inversely, non‐homogeneous pressure distributions lead to lower power densities. Additionally, the measured power density increases when the geometry dependent effective catalytic surface area increases. These results are interesting since they provide an optimization methodology for PEM fuel cells that simplifies and reduces computing requirements, experimentation and manufacturing time.
•Deterministic coherence and anti-coherence resonances were found in small networks of coupled oscillators in in star and star-ring configurations.•Coherence resonance was found in the normalized ...standard deviation of the peak amplitude and inter-peak time interval with respect to the coupling strength.•Coherence resonance was found in the normalized standard deviation of the peak amplitude and inter-peak time interval with respect to frequency mismatch.
We provide compelling numerical evidence of deterministic coherence and anti-coherence resonance in small networks of unidirectional coupled chaotic Rössler oscillators in star and star-ring configurations in the presence of a small mismatch between natural frequencies of the oscillators. The resonance phenomena are found in both the normalized standard deviations of the peak amplitude and inter-peak time interval with respect to the coupling strength and frequency mismatch. The deterministic coherence/anti-coherence resonance resembles self-stabilization/destabilization of the network when the coupling makes collective dynamics more regular/irregular.
Abstract Chronic liver disease and/or portal hypertension may be associated with one of the two pulmonary vascular complications: portopulmonary hypertension and hepatopulmonary syndrome. These ...pulmonary vascular disorders are notoriously underdiagnosed; however, they have a substantial negative impact on survival and require special attention in order to understand their diagnostic approach and to select the best therapeutic options. Portopulmonary hypertension results from excessive vasoconstriction, vascular remodeling, and proliferative and thrombotic events within the pulmonary circulation that lead to progressive right ventricular failure and ultimately to death. On the other hand, abnormal intrapulmonary vascular dilations, profound hypoxemia, and a wide alveolar-arterial gradient are the hallmarks of the hepatopulmonary syndrome, resulting in difficult-to-treat hypoxemia. The aim of this review is to summarize the latest pathophysiologic concepts, diagnostic approach, therapy, and prognosis of portopulmonary hypertension and hepatopulmonary syndrome, as well as to discuss the role of liver transplantation as a definitive therapy in selected patients with these conditions.
This work reports the micromagnetic properties of the strontium hexaferrite (SrM) when its surface is covered with a copper layer. The copper was deposited on the hexaferrite using two different ...methods, one based on the electrochemical deposition and the other one, using the magnetron sputtering technique. For each fabrication method, two different deposition times were selected to vary the copper quantity over the hexaferrite surface. The structural and morphological properties were analyzed from the X-ray diffraction patterns and scanning electron micrographs, while the magnetic behavior was investigated using alternating gradient magnetometry measurements. The samples obtained from chemical electrodeposition exhibited inhomogeneous copper deposits, while the ones obtained from sputtering presented homogeneous and well-distributed copper deposits. The results showed marked differences in the magnetic properties of the hexaferrite with deposited copper regarding the SrM without copper. Also, an improvement in the magnetic properties was observed when a homogeneous copper layer was deposited using sputtering than when electrodeposition was used. When copper was homogeneously deposited, the coercivity (Hc) exhibited an improvement from 2.5 kOe to 3.56 kOe, whereas the remanence squareness (Mr/Ms) increased from 0.5 to 0.7, which is equivalent to 40% increment as a consequence of the copper presence. The changes observed in the hysteresis loops and the dM/dH, H curves indicate that copper exerts a strong interaction on the magnetic moments of hexaferrite. This interaction couples the copper atoms with the interstitial cations of the hexaferrite structure. This copper-iron interaction would occur through a Cu–O–Fe superexchange mechanism, varying the intrinsic properties of the hexaferrite and modifying its micromagnetic behavior.
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