PtCo@NCNTs cathode catalyst using ZIF-67 for proton exchange membrane fuel cell

Zeolitic Imidazolate Frameworks (ZIF) is one of the potential candidates as highly conducting networks with large surface area with a possibility to be used as catalyst support for low temperature fuel cells. In the present study, highly active state-of-the-art PtCo@NCNTs (Nitrogen Doped Carbon Nanotube) catalyst was synthesized by pyrolyzing ZIF-67 along with Pt precursor under flowing ArH₂ atmosphere. The multi-walled NCNTs were densely grown on the surface of ZIF particles after pyrolysis. The high resolution TEM examination was employed to examine the nature of the PtCo particles as well as multi-walled NCNTs. Rotating disk electrode study was used for measuring oxygen reduction reaction performance for PtCo@NCNTs in 0.1 M HClO₄ and compared with commercial Pt/C catalyst. Fuel cell performance with PtCo@NCNT and commercial Pt/C catalysts was evaluated at 70 °C using Nafion-212 electrolyte using H₂ and O₂ gases (100% RH) and the observed peak power density of 630 and 560 mW cm^?2, respectively.     

One-step synthesis of the 3D flower-like heterostructure MoS2/CuS nanohybrid for electrocatalytic hydrogen evolution

In this work, a facile one-step hydrothermal method was developed to fabricate three types different of nanomaterials: the two-dimension (2D) of MoS₂ nanosheets; 3D spherical CuS nanoparticles; and 3D flower-like heterostructure of MoS₂/CuS nanohybrid, respectively. The as-synthesized MoS₂, CuS and MoS₂/CuS were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (SEM) and X-ray diffraction (XRD) etc. The morphology of the MoS₂/CuS nanohybrid is different from the MoS₂ nanosheets and CuS nanoparticles. The hydrogen evolution reaction (HER) activity of MoS₂ nanosheets, CuS nanoparticles and MoS₂/CuS nanohybrid, were investigated by the Linear Sweep Voltammetry (LSV) and Tafel slope. The HER activity of MoS₂/CuS nanohybrid is better than those of MoS₂ nanosheets and CuS nanoparticles, which can be attributed to the good electron-transport ability of CuS and the strong reduction ability of hydrogen ions by MoS₂. Thus, MoS₂/CuS nanohybrid exhibited excellent activity for HER with a small onset potential of 0.15 V, a low Tafel slope of 63 mV dec^?1, and relatively good stability. However, the MoS₂ nanosheets and CuS nanoparticles respectively shows a bigger onset potential of 0.25 V and 0.35 V, a higher Tafel slope of 165 and 185 mV dec^?1. This 3D flower-like heterostructure of MoS₂/CuS nanohybrid catalyst exhibits great potential for renewable energy applications.     

Inspection and maintenance of oil & gas pipelines: a review of policies

Oil and gas (O&G) pipelines are expensive assets that cross through both the ecologically sensitive and densely populated urban areas. The pipeline failure may have potentially significant consequences for both the natural and human environments. In order to maintain the integrity of O&G pipelines, inspection and maintenance processes should be governed by efficient policies. The objective of this paper is to conduct a state-of-the-art review of maintenance policies of O&G pipelines to investigate their advantages, limitations, and associated implementation issues. Maintenance policies can be categorised into corrective, preventive, predictive and proactive. Corrective maintenance policies (1940s) were based on the ‘repair when broke’ philosophy. Economic considerations shifted practice towards preventive maintenance (1970s to 1990s); later with improved inspection techniques and environmental regulations, predictive and proactive or risk-based maintenance (RBM) policies were developed. This review explicates different methodologies for RBM and related issues, e.g. uncertainties and variability, conservative assumptions, etc. Uncertainties associated with investigation and prediction of defects have been more frequently reported in the literature so far. Moreover, existing studies primarily focused on reducing the likelihood and cost of failure, whereas consideration of environmental factors in overall risk has been a relatively less addressed issue.     

Theoretical Investigation for Exploring the Antioxidant Potential of Chlorogenic Acid: A Density Functional Theory Study

The main objective of this research was to conduct a theoretical investigation into the antioxidant properties of chlorogenic acid. Calculations based on the density functional theory were performed using the B3LYP exchange-correlation functional and the 6-311G standard basis set to determine the theoretical parameters, such as bond dissociation enthalpy and spin density. H atom abstraction from ?OH groups was the most representative reaction pathway chosen for this study. From these calculations, it was estimated that bond dissociation enthalpies of hydroxyl groups were in the order of 3’-OH > 4’-OH > 2-OH > 1-OH. Spin densities of O-atoms of free radicals formed (after the removal of H atoms) from the hydroxyl groups of aromatic rings were lower than that of hydroxyl groups of alicyclic rings. On the basis of the calculated results, H atom abstraction from ?OH groups of aromatic ring should be the main mechanism for the antioxidant potential of chlorogenic acid. Moreover, a comparison of bond dissociation enthalpy values for different phenolic acid antioxidants showed that the chlorogenic acid is a potent antioxidant. This theoretical investigation might be helpful for the future applications of chlorogenic acid in the field of the pharmacy and food industries.     

Feeding barley grain steeped in lactic acid modulates rumen fermentation patterns and increases milk fat content in dairy cows

The objectives of the present in vivo and in situ trials were to evaluate whether feeding barley grain steeped in lactic acid (LA) would affect rumen fermentation patterns, in situ dry matter (DM) degradation kinetics, and milk production and composition in lactating dairy cows. The in vivo trial involved 8 rumen-fistulated Holstein cows fed once daily a total mixed ration containing rolled barley grain (27% in DM) steeped for 48 h in an equal quantity of tap water (CTR) or in 0.5% LA (TRT) in a 2 × 2 crossover design. The in situ trials consisted of incubation of untreated rolled barley grain in cows fed CTR or TRT diets and of incubation of 3 different substrates including CTR or barley grain steeped in 0.5% or 1.0% LA (TRT1 and TRT2, respectively) up to 72 h in the rumen. Results of the in vivo trial indicated that cows fed the TRT diet had greater rumen pH during most intensive fermentation phases at 10 and 12 h post-feeding. The latter effect was associated with a shorter duration in which rumen pH was below 5.8 for cows fed the TRT diet (2.4 h) compared with CTR diet (3.9 h). Furthermore, cows fed the TRT diet had lower concentrations of volatile fatty acids at 2 and 4 h post-feeding. In addition, concentrations of preprandial volatile fatty acids were lower in the rumen fluid of cows fed the TRT diet. Results also showed that molar proportion of acetate was lower, whereas propionate tended to increase by feeding cows the TRT diet. Cows fed the TRT diet demonstrated greater rumen in situ lag time of substrate DM degradation and a tendency to lower the fractional degradation rate. Other in situ results indicated a quadratic effect of LA on the effective rumen degradability of substrates whereby the latter variable was decreased from CTR to TRT1 but increased for TRT2 substrate. Although the diet did not affect actual milk yield, fat-corrected milk, percentages of milk protein, and lactose and concentration of milk urea nitrogen, cows fed the TRT diet increased milk fat content and tended to increase fat:protein ratio in the milk. In conclusion, results demonstrated that treatment of barley grain with LA lowered the risk of subacute rumen acidosis and maintained high milk fat content in late-lactating Holstein cows fed diets based on barley grain.     

Microemulsions as a Surrogate Carrier for Dermal Drug Delivery

Microemulsions are isotropic, thermodynamically stable transparent (or translucent) systems of oil, water, and surfactant, frequently in combination with a cosurfactant with a droplet size usually in the range of 20–200 nm. Since their discovery, they have attained increasing significance both in basic research and in industry. Due to their distinct advantages such as enhanced drug solubility, thermodynamic stability, facile preparation, and low cost, uses and applications of microemulsions have been numerous. Recently, there is a surge in the exploration of microemulsion for transdermal drug delivery for their ability to incorporate both hydrophilic (5-fluorouracil, apomorphine hydrochloride, diphenhydramine hydrochloride, tetracaine hydrochloride, and methotrexate) and lipophilic drugs (estradiol, finasteride, ketoprofen, meloxicam, felodipine, and triptolide) and enhance their permeation. Very low surface tension in conjunction with enormous increase in the interfacial area due to nanosized droplets of the microemulsion influences the drug permeation across the skin. A large number of oils and surfactants are available, which can be used as components of microemulsion systems for transdermal delivery but their toxicity, irritation potential, and unclear mechanism of action limit their use. Besides surfactants, oils can also act as penetration enhancers (oleic acid, linoleic acid, isopropyl myristate, isopropyl palmitate, etc.). The transdermal drug delivery potential of microemulsions is dependent not only on the applied constituents of the vehicle but also drastically on the composition/internal structure of the phases which may promote or hamper the drug distribution in the vehicles. This article explores microemulsion as transdermal drug delivery vehicles with emphasis on components selection for enhanced drug permeation and skin tolerability of these systems and further future directions.     

Early stage disentanglement and non-Markovianity

We have studied an early stage disentanglement by solving an exactly solvable spin bath model in the Markovian and non-Markovian regimes. In the Markovian regime, the central two qubit spins are non-interacting in which entanglement strongly depends on mean number of photon. In the non-Markovian regime, we solved by considering and ignoring the interaction between central two spins and observe that the entanglement strongly depends on the spin bath interaction, qubit spin interaction, bath spin interaction, thermal temperature and the initial state. Further, the concurrence of an initially unentangled state mixed with an entangled state also depends on the initial state.     

Preparation and characterization of K-substituted NaCa4Nb5O17 microwave dielectric ceramics

The effect of K substitution for Na on the phase, microstructure and microwave dielectric properties of the Na_1?x K _x Ca₄Nb₅O₁₇ (x = 0–1) composition series was investigated. The compositions with x = 0, 0.5 and 1 formed single-phase Na_1?x K _x Ca₄Nb₅O₁₇ ceramics within the detection limit of the in-house XRD facility when sintered at 1,200–1,300 °C. At x = 0.25 and 0.75, the major Na_1?x K _x Ca₄Nb₅O₁₇ phase formed but along with a secondary CaNb₂O₆ phase. Relative permittivity (ε _r ) and temperature coefficient of resonant frequency (τ_f) increased from 45 to 51 and ?120 to +473 ppm/ °C respectively while the quality factor (Q × f _o ) decreased from 13,838 to 2,374 GHz with an increase in x from 0 to 1. Optimum microwave dielectric properties (i.e. ε _r  = 47, Q × f _o  = 5,047 GHz and τ_f = ? 23 ppm/ °C) were achieved for the x = 0.5 (i.e. Na_0.5K_0.5Ca₄Nb₅O₁₇) composition. Further investigations are required to improve the density and hence microwave dielectric properties of Na_1?x K _x Ca₄Nb₅O₁₇ ceramics.