Nanoparticle using parallel split rings and implementation of chain for creating Fano resonance with polarization independence for energy harvesting in mid-infrared

In optical devices, the polarization of the incident wave affects the Nano particle characteristics. Therefore, designing a polarization-independent device is significant in the process of designing optical structures. On the other hand, the concept of Fano resonance and dark mode has been utilized for achieving more energy enhancement. In this paper, we have developed a symmetrical Nano antenna by employing Fano resonance, which is independent of the incident wave polarization. The proposed Nano antenna is modified in mid infrared regime for biosensing and energy harvesting applications. The designed metamaterial antenna is made by Nano split ring resonators with etched capacitive gaps, which are utilized for concentrating energy. The introduced Nano antenna has a bright and dark mode with a weak enhancement of electric field. The effect of the incident wave polarization is investigated at wave incident angles between 0° and 45° to illustrate the independency of the polarization due to the symmetrical shape of the Nano antenna. In order to trigger the dark mode and enhance the electric field, a Nano chain is incorporated in the final structure. This arrangement has led to increasing of electric field drastically. Furthermore, the figure of merit has been calculated as an advantageous factor in sensing the surrounding materials with various refractive indices. Our findings illustrated that the chain arrangement has caused a peak in the linear form of the extinction cross section of the Nano antenna. This in turn has resulted in the appearance of Fano resonance with no impact on the resonance frequency that has been originally adjusted by capacitive gaps and inductive strips.     

Leading students towards the formal world of mathematical thinking: a mathematician’s reflections on teaching eigentheory

ABSTRACT

In this study, we analysed a mathematician’s teaching journals on eigenvalues and eigenvectors in a first-year linear algebra course. The research team employed Tall’s [How humans learn to think mathematically: Exploring the three worlds of mathematics. Cambridge University Press] three-world model of embodied, symbolic and formal as a framework for understanding the mathematician and teacher’s pedagogical reflections as he led the class to the formal world. In order to reach the formal world, he used a sequence of tasks that emphasized embodied and symbolic, as well as formal thinking. The analysis of the journals showed that the mathematician faced challenges in leading the class towards the formal world. The study also revealed that the mathematician strived to build a concept image, that, while perhaps mirroring his own, did not resonate with the students.     

Sodium Butylated Hydroxytoluene (NaBHT) as a New and Efficient Hydride Source for Pd-Catalysed Reduction Reactions

NaBHT (sodium butylated hydroxytoluene), a hindered and soluble base for the efficient arylation of various base-sensitive amines and (hetero)aryl halides has been found to have an unanticipated role as a hydride donor to reduce (hetero)aryl halides and allylic acetates. Mechanistic studies have uncovered that NaBHT, but not BHT, can deliver multiple hydrides through oxidation of the benzylic methyl group in NaBHT to the aldehyde. Further, performing the reduction with NaBHT-d₂₀ has revealed that the redox-active benzylic position is not the only hydride donor site from NaBHT with one hydride in three coming, presumably, from the tert-butyl groups. The reduction works well under mild conditions and, incredibly, only consumes 20 percent of the NaBHT in the process; the remaining 80 percent can be readily recovered in pure form and reused. This, combined with the low cost of the material in ton-scale quantity, makes it practical and attractive for wider use in industry at scale.     

Evaluation of the reaction mechanism for photocatalytic degradation of organic pollutants with MIL-88A/BiOI structure under visible light irradiation

Research on Chemical Intermediates - In this study, we synthesized novel visible light photocatalyst MIL-88A/BiOI using depositing BiOI particles on the surface of a metal–organic framework...     

Hyperpolarizing Concentrated Metronidazole 15NO2 Group over Six Chemical Bonds with More than 15 % Polarization and a 20 Minute Lifetime

The NMR hyperpolarization of uniformly ¹⁵N-labeled [¹⁵N₃]metronidazole is demonstrated by using SABRE-SHEATH. In this antibiotic, the ¹⁵NO₂ group is hyperpolarized through spin relays created by ¹⁵N spins in [¹⁵N₃]metronidazole, and the polarization is transferred from parahydrogen-derived hydrides over six chemical bonds. In less than a minute of parahydrogen bubbling at approximately 0.4 μT, a high level of nuclear spin polarization (P_15N) of around 16 % is achieved on all three ¹⁵N sites. This product of ¹⁵N polarization and concentration of ¹⁵N spins is around six-fold better than any previous value determined for ¹⁵N SABRE-derived hyperpolarization. At 1.4 T, the hyperpolarized state persists for tens of minutes (relaxation time, T₁≈10 min). A novel synthesis of uniformly ¹⁵N-enriched metronidazole is reported with a yield of 15 %. This approach can potentially be used for synthesis of a wide variety of in vivo metabolic probes with potential uses ranging from hypoxia sensing to theranostic imaging.     

Structural and functional analysis of a novel psychrophilic β-mannanase from Glaciozyma antarctica PI12

The structure of a novel psychrophilic β-mannanase enzyme from Glaciozyma antarctica PI12 yeast has been modelled and analysed in detail. To our knowledge, this is the first attempt to model a psychrophilic β-mannanase from yeast. To this end, a 3D structure of the enzyme was first predicted using a threading method because of the low sequence identity (<30 %) using MODELLER9v12 and simulated using GROMACS at varying low temperatures for structure refinement. Comparisons with mesophilic and thermophilic mannanases revealed that the psychrophilic mannanase contains longer loops and shorter helices, increases in the number of aromatic and hydrophobic residues, reductions in the number of hydrogen bonds and salt bridges and numerous amino acid substitutions on the surface that increased the flexibility and its efficiency for catalytic reactions at low temperatures.     

Insight into the solvent effect on the structure,IR-spectrum,and hyperpolarizability of CpMe<Subscript>2</Subscript>Ta(benzyne), a mononuclear Tantalum–benzyne complex

In this investigation, quantum chemical calculations using MPW1PW91 method were applied to analyze of the solvent effect on the structural, vibrational analysis, thermochemical parameters and first hyperpolarizability for CpMe₂Ta(benzyne) complex. The solvent effects on the structure and properties were examined by the self-consistent reaction field theory (SCRF) based on Polarizable Continuum Model (PCM). Good correlations exist between these parameters and dielectric constants of solvents. The wavenumbers of the IR-active symmetric stretching vibrations of Ta-Me in different solvents were correlated with the Kirkwood–Bauer–Magat equation (KBM). In addition, Monte Carlo simulations using standard procedure of Metropolis sampling were applied to investigate of the solvation of CpMe₂Ta(benzyne) complex. In addition, the bonding interaction between the CpTaMe₂ and benzyne fragments was analyzed by means of the energy decomposition analysis (EDA).     

Molecular dynamics simulation of nonsteroidal antiinflammatory drugs,naproxen and relafen,in a lipid bilayer membrane

Naproxen and relafen, as nonsteroidal antiinflammatory drugs, were simulated in neutral and charged forms and their effects on a lipid bilayer membrane were investigated by molecular dynamics simulation using Groningen machine for chemical simulations software (GROMACS). Simulation of 10 systems was performed, which included different dosages of the drug molecules, naproxen and Relafen, in charged and neutral forms, and a mixture of naproxen and Relafen in neutral forms. The effects of the mixture and the individual drugs' dosages on membrane properties, such as electrostatic potential, order parameter, diffusion coefficients, and hydrogen bond formation, were analyzed. Hydration of the drugs in the membrane system was investigated using radial distribution function analysis. Using fully hydrated dimyristoylphosphatidylcholine (DMPC) as a reference system, 128 lipid molecules and water molecules were simulated exclusively, and the same simulation technique was performed on 10 other systems, including drug mixtures and a DMPC membrane. Angular distributions of lipid chains of the membrane were calculated, and the effects of the drug insertion and chain orientation in the membrane were evaluated. © 2013 Wiley Periodicals, Inc.     

Photophysical Properties and Kinetic Studies of 2-Vinylpyridine-Based Cycloplatinated(II) Complexes Containing Various Phosphine Ligands

A series of cycloplatinated(II) complexes with general formula of [PtMe(Vpy)(PR₃)], Vpy = 2-vinylpyridine and PR₃ = PPh₃ (1a); PPh₂Me (1b); PPhMe₂ (1c), were synthesized and characterized by means of spectroscopic methods. These cycloplatinated(II) complexes were luminescent at room temperature in the yellow–orange region’s structured bands. The PPhMe₂ derivative was the strongest emissive among the complexes, and the complex with PPh₃ was the weakest one. Similar to many luminescent cycloplatinated(II) complexes, the emission was mainly localized on the Vpy cyclometalated ligand as the main chromophoric moiety. The present cycloplatinated(II) complexes were oxidatively reacted with MeI to yield the corresponding cycloplatinated(IV) complexes. The kinetic studies of the reaction point out to an S_N2 mechanism. The complex with PPhMe₂ ligand exhibited the fastest oxidative addition reaction due to the most electron-rich Pt(II) center in its structure, whereas the PPh₃ derivative showed the slowest one. Interestingly, for the PPhMe₂ analog, the trans isomer was stable and could be isolated as both kinetic and thermodynamic product, while the other two underwent trans to cis isomerization.