Minimum Path Problems in Normed Spaces: Reflection and Refraction

The paper deals with the existence and characterization of minimum or extremum paths connecting two given points in a vector space, which is divided by a barrier (a curve C if the space is 2-dimensional) into two parts with different norms. The global problem of existence of polygonal paths of shortest length is dealt with in Section 2. An example shows that, for a curve with a point of inflection, such paths may not exist. However, the existence of such paths is proved for a more restricted class of curves (Theorem 2.3). The notion of permissible polygonal paths is introduced, and it is shown that, for a very general class of curves, such paths of shortest length do exist (Theorem 2.2).Sections 3 and 4 deal with the local conditions at the intersection of the extremal path with the curve C. Theorem 4.1 establishes a geometric characterization of the point of intersection, and Eqs. (13) and (15) are formulas for the angles that the segments of the extremal path make with a fixed axis or with the normal to C at the point of intersection. The case where the unit circles of the tax norms are Euclidean circles with different radii leads to the traditional Snell law. Section 6 deals with the law of reflection at the curve C, which in the case of the Euclidean norm asserts the equality of the angles of incidence and reflection. The n-dimensional case, where the curve C is replaced by a hypersurface, is considered briefly in Section 7.     

Impact of Surface Defects on LaNiO3 Perovskite Electrocatalysts for the Oxygen Evolution Reaction

Perovskite oxides are regarded as promising electrocatalysts for water splitting due to their cost-effectiveness, high efficiency and durability in the oxygen evolution reaction (OER). Despite these advantages, a fundamental understanding of how critical structural parameters of perovskite electrocatalysts influence their activity and stability is lacking. Here, we investigate the impact of structural defects on OER performance for representative LaNiO₃ perovskite electrocatalysts. Hydrogen reduction of 700 °C calcined LaNiO₃ induces a high density of surface oxygen vacancies, and confers significantly enhanced OER activity and stability compared to unreduced LaNiO₃; the former exhibit a low onset overpotential of 380 mV at 10 mA cm⁻² and a small Tafel slope of 70.8 mV dec⁻¹. Oxygen vacancy formation is accompanied by mixed Ni²⁺/Ni³⁺ valence states, which quantum-chemical DFT calculations reveal modify the perovskite electronic structure. Further, it reveals that the formation of oxygen vacancies is thermodynamically more favourable on the surface than in the bulk; it increases the electronic conductivity of reduced LaNiO₃ in accordance with the enhanced OER activity that is observed.     

Common Pitfalls of Reporting Electrocatalysts for Water Splitting

Rigorous assessment of heterogeneous electrocatalysts for electrochemical water splitting has been a critical issue mainly due to insufficient standard protocols to measure and report experimental data. In this perspective, we highlight some common pitfalls when measuring and reporting electrocatalytic data, which should be avoided to ensure the accuracy and reproducibility and to advance the water splitting field. We advocate to prevent the introduction of artefacts from the counter and reference electrodes, as well as the impurities in the electrolyte when conducting electrocatalyst activity measurements. In addition, we encourage the use of the electrochemically active surface area(ECSA)-normalized current densities to represent the intrinsic activity of the reported catalysts for a better comparison with previously known materials. Suitable ECSA measurement methods should be employed based on the nature of catalysts. Recommendations made in this perspective will hopefully assist in identifying advanced catalysts for water splitting research.     

Effect of amphoteric surfactant on phase behavior of hydrocarbon-electrolyte-water system-an application in enhanced oil recovery

The different techniques such as enhanced oil recovery (EOR) and improved oil recovery (IOR) have been used to enhance oil production. The surfactant flooding is a tertiary oil recovery technique that has been widely used in oil field industry. A variety of surfactant chemicals have been used in which among them the amphoteric type, which has two groups of opposite charges, needs more investigation. In this work, we use cocamidopropyl betaine as an amphoteric surfactant that is used to investigate its influence on the aquifer?+?hydrocarbon system. The effects of surfactant concentration, salinity, and hydrocarbon type on the phase behavior of the various saline aqueous-hydrocarbon mixtures are investigated. Moreover, the surfactant flooding is carried out using a glass micromodel. Thus, to investigate the wettability, the contact angle is also measured for the present system that it is an influential factor in oil recovery. First, by increasing salinity from 0?wt% to 20?wt% in n-hexadecane, the phase change take placed so that a Winsor formation from type I to III and then to type II occurs. However, for n-heptane upon enhancing salinity, Winsor type III is transformed to type II so that hydrocarbon (oil) recovery increases and break through occurs with a delay. By increasing salinity, water solubilization parameter decreases for both hydrocarbon and by enhancing both surfactant concentration and salinity leads to reduce the contact angle. Thus, cocamidopropyl betaine works better for the longer hydrocarbon chain.

In the micromodel flooding test upon formation of Winsor II, the recovery is higher and the break through takes place with a delay. However, for the case of Winsor I, the recovery is lower and the break through occurs earlier. Finally, one can conclude that the low concentration of amphoteric surfactants needs to use that plays an important role in chemical EOR and results a higher recovery in high salinity.     

Thermal Stress Analysis of a Continuous and Pulsed End-Pumped Nd:YAG Rod Crystal Using Non-Classic Conduction Heat Transfer Theory

In this paper, temperature distribution in the continuous and pulsed end-pumped Nd:YAG rod crystal is determined using nonclassical and classical heat conduction theories. In order to find the temperature distribution in crystal, heat transfer differential equations of crystal with consideration of boundary conditions are derived based on non-Fourier’s model and temperature distribution of the crystal is achieved by an analytical method. Then, by transferring non-Fourier differential equations to matrix equations, using finite element method, temperature and stress of every point of crystal are calculated in the time domain. According to the results, a comparison between classical and nonclassical theories is represented to investigate rupture power values. In continuous end pumping with equal input powers, non-Fourier theory predicts greater temperature and stress compared to Fourier theory. It also shows that with an increase in relaxation time, crystal rupture power decreases. Despite of these results, in single rectangular pulsed end-pumping condition, with an equal input power, Fourier theory indicates higher temperature and stress rather than non-Fourier theory. It is also observed that, when the relaxation time increases, maximum amounts of temperature and stress decrease.     

Bovine serum albumin stabilized iron oxide and gold bimetallic heterodimers: Synthesis,characterization and Stereological study

In this time researchers make a great efforts to develop new hybrid nanoparticles for medical and pharmaceutical applications. Fe₃O₄‐Au hybrid heterodimers have been prepared with superior properties for various claims. Unfortunately, Fe₃O₄‐Au heterodimers are not stable in the physiological medium. In this study, we employed the albumin macromolecules as a stabilizer of Fe₃O₄‐Au hybrid nanoparticles (noted as Fe₃O₄‐Au‐BSA hybrid nanoparticles). After characterization of synthesized nanoparticles by FTIR, UV–Vis, TEM, DLS, DSC, VSM and XRD techniques, the in vitro and in vivo biocompatibility of these nanoparticles were also evaluated. We encountered with an amazing result which confirmed nanoparticles could be stabilized by linking the BSA on the surface of Fe₃O₄‐Au heterodimers. Also, intravenous injection of Fe₃O₄‐Au‐BSA hybrid nanoparticles up to 400 mg/kg to Balb C mice show that these nanoparticles were non‐toxic. The biocompatibility and stereological study had been performed for more than 30 days after nanoparticles administration, using hystomorphometric analysis. Remarkably, to the best of our knowledge, it was the first time the biocompatibility and biodegradability of Fe₃O₄‐Au were studied and evaluated by stereological technique. Further promotion and biomedical usage of this type of hybrid nanoparticles are underway in our laboratory.     

Stability of characters and filters for weighted semilattices

Semigroup Forum - We continue the study of the AMNM property for weighted semilattices that was initiated in Choi (J Aust Math Soc 95(1):36–67, 2013. https://doi.org/10.1017/S1446788713000189...     

Low-frequency Vibrational Modes in Small Polypeptides of Essential Amino Acids

Optics and Spectroscopy - The length-dependent low-frequency terahertz absorption spectrum of the essential amino acid chains has been investigated. Since this special type of amino acids cannot be...     

The effect of the hydrogen fluoride chain on the aromaticity of C6H6 in the C6H6···(HF)1–4 complexes

The effect of the hydrogen fluoride chain ((HF)_n) on the aromaticity and π character of C–C bonds of C₆H₆ in the C₆H₆···(HF)_n (n = 1–4) complexes were investigated using density functional theory employing RM05 functional. It was found that the binding energy between C₆H₆ and different (HF)_n chains showed a maximum at n = 3 (C₆H₆···(HF)₃). Also, the π–hydrogen interaction (πHI) and the bifurcated fluorine interaction (BFI) increased and decreased the π character of the C–C bond of C₆H₆, respectively. In addition, the change of aromaticity of the C₆H₆ due to the interaction with the HF chains was also studied using three different aspects such as aromatic fluctuation index (FLU), average two centre index (ATI) and proton nuclear magnetic resonance (HNMR) spectrum. The most change in the aromaticity happens when the C₆H₆ interacts with (HF)₃ chain. The variation of aromaticity with the binding energy and the summation of two-body terms were investigated and very good linear correlations were observed.