334 research outputs found
Ni3S4/NiS/rGO as a promising electrocatalyst for methanol and ethanol electro-oxidation
No full textWe present a one-step hydrothermal synthesis of hybrids consisting of nickel sulfides in the form of Ni3S4-NiS (NN) and Ni3S4–NiS-rGO (NNR), i.e. with the addition of reduced graphene oxide (rGO), for application as catalysts. After accurate physical characterization and confirmation of
the successful synthesis, we evaluate the ability of these catalysts in the processes of methanol and ethanol oxidation. The precise electrochemical analyses show relatively good potential and excellent cyclic stability in methanol oxidation reaction and ethanol oxidation reaction processes.
The comparison of the two catalysts shows the superiority of NNR over NN confirming that rGO introduces a higher specific surface area and a higher electrical conductivity in the NNR structure.
In the process of MOR, NNR has an oxidation peak at a current density of 55 mA cm–2 and a peak potential of 0.54 V. In EOR, this peak is located at a current density of 11 mA cm–2 and at a peak potential of 0.59 V. NNR has 97% and 94% stability in MOR and EOR after 1000 consecutive cycles, respectively which are acceptable values
MnCo2O4/NiCo2O4/rGO as a Catalyst Based on Binary Transition Metal Oxide for the Methanol Oxidation Reaction
No full textThe demands for alternative energy have led researchers to find effective electrocatalysts in fuel cells and increase the efficiency of existing materials. This study presents new nanocatalysts based on two binary transition metal oxides (BTMOs) and their hybrid with reduced graphene oxide for methanol oxidation. Characterization of the introduced three-component composite, including cobalt manganese oxide (MnCo2O4), nickel cobalt oxide (NiCo2O4), and reduced graphene oxide (rGO) in the form of MnCo2O4/NiCo2O4/rGO (MNR), was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray (EDX) analyses. The alcohol oxidation capability of MnCo2O4/NiCo2O4 (MN) and MNR was evaluated in the methanol oxidation reaction (MOR) process. The crucial role of rGO in improving the electrocatalytic properties of catalysts stems from its large active surface area and high electrical conductivity. The alcohol oxidation tests of MN and MNR showed an adequate ability to oxidize methanol. The better performance of MNR was due to the synergistic effect of MnCo2O4/NiCo2O4 and rGO. MN and MNR nanocatalysts, with a maximum current density of 14.58 and 24.76 mA/cm2 and overvoltage of 0.6 and 0.58 V, as well as cyclic stability of 98.3% and 99.7% (at optimal methanol concentration/scan rate of 20 mV/S), respectively, can be promising and inexpensive options in the field of efficient nanocatalysts for use in methanol fuel cell anodes
CeO2-NiO-rGO as a nano-electrocatalyst for methanol electro-oxidation
No full textThis study provides the methanol oxidation capability of two nanocatalysts, CeO2-NiO (CN) and CeO2-NiO-rGO (CNR), synthesized by a cost-effective hydrothermal method. The synergistic effect of compositing CeO2-NiO with reduced graphene oxide was evaluated. These synergic effect makes a good electrochemical active surface area and suitable electrical conductivity for catalyst. In addition, rGO with good electrical conductivity revealed considerable improvement in the methanol oxidation reaction (MOR) performance of the catalyst. The cyclic stability measurements of CeO2-NiO-rGO showed a high retention ability of 96% in 500 consecutive CV cycles, while the stability of CeO2-NiO in the same number of cycles is about 93%. The complementary methanol oxidation process results indicated an oxidation current density up to 49.5 and 68.5 mA/cm2 for CN and CNR at a scan rate of 20 mV/s, respectively. The proposed catalyst can be considered as an attractive, stable, and inexpensive candidate in the field of methanol oxidation to use in methanol fuel cells
<i>Riga-Fede disease</i>: A histological study and case report
No full textAcute traumatic ulcerations and granulomas of the oral mucosa may result from physical damage via sharp foodstuffs, accidental biting, or talking. Most ulcerations heal within days. Others become chronic, reactive, and exophytic. A histopathologically unique type of chronic traumatic ulceration is the traumatic ulcerative granuloma with stromal eosinophilia (TUGSE). TUGSE exhibits a deep "pseudoinvasive" inflammatory reaction. This lesion may occur under the tongue in infants as a result of chronic mucosal trauma caused by mandibular anterior primary teeth during nursing and is termed Riga-Fede disease (RFD). The clinical presentation many resemble squamous cell carcinoma causing concern. RFD, although not uncommon, is not frequently reported. Thus, dental practitioners are unfamiliar with such lesions. We present a large Riga-Fede lesion in an infant along with the clinical management
Modifications on nucleon parameters at finite temperature
No full textAzizi, Kazem (Dogus Author)Taking into account the additional operators coming up at finite temperature, we investigate the mass and residue of the nucleon in the framework of thermal QCD sum rules. We observe that the mass and residue of the nucleon are initially insusceptible to the increase of temperature, however, after a certain temperature, they start to fall with increasing the temperature
Decuplet baryons in a hot medium
No full textAzizi, Kazem (Dogus Author) -- Bozkır, G. (Dogus Author)The thermal properties of the light decuplet baryons are investigated in the framework of the thermal QCD sum rules. In particular, the behavior of the mass and residue of the Delta, Sigma*, Xi*, and Omega baryons with respect to temperature are analyzed taking into account the additional operators appearing in the Wilson expansion at finite temperature. It is found that the mass and residue of these particles remain overall unaffected up to T similar or equal to 150 MeV but, beyond this point, they start to diminish considerably
Magnetic dipole moment of Z(b)(10610) in light-cone QCD
No full textAzizi, Kazem (Dogus Author) -- Özdem, Ulaş (Dogus Author)The magnetic dipole moment of the exotic Z(b)(10610) state is calculated within the light cone QCD sum rule method using the diquark-antidiquark and molecule interpolating currents. The magnetic dipole moment is obtained as mu(Zb) = 1.73 +/- 0.63 mu(N) in diquark-antidiquark picture and mu(Zb) = 1.59 +/- 0.58 mu(N) in the molecular case. The obtained results in both pictures together with the results of other theoretical studies on the spectroscopic parameters of the Zb(10610) state may be useful in determination of the nature and quark organization of this state
Effects of repeated hydraulic loads on microstructure and hydraulic behaviour of a compacted clayey silt
No full textSoils used in earth constructions are mostly unsaturated, and they undergo frequent drying-wetting cycles (repeated hydraulic loads) due to changes in climatic conditions or variations of the ground water level, particularly at shallow depths. After compaction, changes in water content can significantly influence the hydromechanical response of the construction material, which therefore has to be assessed for repeated hydraulic loads. This research investigates the effect of such loads on the microstructure and hydraulic behaviour of a silty soil, typically used in the construction of embankments and dykes, with the aim of providing a better understanding of the consequences of drying-wetting cycles on the response of the material over time. Experimental tests were performed to study the impact of drying-wetting cycles on the water retention, hydraulic conductivity and fabric of compacted specimens. Fabric changes are documented to take place even without significant volumetric strains, promoting an irreversible increase in the hydraulic conductivity and a reduction in the capacity to retain water compared to the as-compacted soil. The fabric changes are interpreted and quantified by means of a hydromechanical model, which accounts for the evolving pore size distribution at different structural levels. The proposed model reproduces quite well the microstructural observations, together with the evolution of the water retention behaviour and of the hydraulic conductivit
Thermal behavior of the mass and residue of hyperons
No full textAzizi, Kazem (Dogus Author) -- Kaya, Gülşah (Dogus Author)We investigate the mass and residue of Sigma, Lambda and Xi hyperons at finite temperature in the framework of thermal QCD sum rules. In our calculation, we take into account the additional operators coming up at finite temperature. We find the temperature-dependent continuum threshold for each hyperon using the obtained sum rules for their mass and residue. The numerical results demonstrate that the mass and residue of the particles under consideration remain stable up to a certain temperature, after which they decrease by increasing the temperature
A microstructure-based elastoplastic model to describe the behaviour of a compacted clayey silt in isotropic and triaxial compression
No full textThe paper focuses on the hydro-mechanical behaviour of an unsaturated compacted clayey silt, accounting for fabric changes induced by drying-wetting cycles occurring at low-stress levels. The response along isotropic compression and triaxial compression (shear) at constant water content was investigated by laboratory tests on both as compacted and dried-wetted samples. Compaction induces a micro-structural porosity pertinent to clay peds and a macro-structural porosity external to the peds. Drying-wetting cycles decrease the micro-porosity and increase the macro-porosity, which reduces the water retention capacity, increases the compressibility and promotes higher peak strengths with more brittle behaviour during triaxial compression. A coupled double porosity elastic-plastic model was formulated to simulate the experimental results. A non-associated flow rule was defined for the macrostructure, modifying a stress-dilatancy relationship for saturated granular soils to account for the increase in dilatancy with suction observed in the experiments. The average skeleton stress and suction were adopted as stress variables. Consistently with model predictions, the shear strength at critical state is not significantly influenced by the degree of saturation or by the hydraulic history. On the other contrary, the higher peak strength, brittleness and dilatancy of the dried wetted samples are mostly explained by their reduced water retention capacity
- …
