Partial widths and branching ratios for the emitted electron resulting from interatomic Coulombic decay in quantum wells heterostructure

Interatomic coulomb decay (ICD) is a decay process relying on the Coulombic interaction between neighbouring atoms, molecules or nanostructures. Due to this process, an electron is emitted into the continuum. We study the ICD process in a system of the double quantum well heterostructure and investigate how we can manipulate the structure's parameters such that a better detection of the ICD's emitted electron is achieved. For this purpose, we calculated the partial widths (PWs) and branching ratios (BRs) of the ICD's emitted electron to the left and right asymptotes of the heterostructure; these will give an estimation of the detection current. We manipulated the structure's parameters and took into account the repulsion from the electron in the ground state located in the left well. By introducing two small barriers in the vicinity of the right QW, we observed a BR three times larger than in the structure without the barriers. We also investigate the effect of repulsion due to the second electron. This work gives a better understanding of the dynamics of the scattered ICD's electron, and realisation of better design rules for future experimental observation of ICD in nanostructures.     

Electron spin resonance (ESR/EPR) of free radicals observed in human red hair: a new,simple empirical method of determination of pheomelanin/eumelanin ratio in hair

The definition of the concentration of pheomelanin in the skin is an issue of great interest because in the case of being influenced by UV radiation, it manifests itself as a prooxidant, causing various skin disorders including melanoma that might help to explain the relatively high incidence of skin cancer among individuals with red hair. The ESR spectra of red hair samples were investigated. It was found that at low microwave power, they are characterized by two types of spectra. Red hair ESR signals result from a superposition of two spectral shapes, a singlet spectrum as a result of the existence of eumelanin and a triplet spectrum as a result of the existence of pheomelanin. At high microwave power, only triplet spectra shape was detected, caused by saturation of the eumelanin singlet. Using different concentration ratios of black to red hair, we measured ESR spectra and plotted the ratio values in each sample against a measured ‘g‐factor’ (experimental). We found that there is a linear relationship between these two parameters. So, it is evident that using these results, the concentration ratio of pheomelanin to eumelanin in a sample of hair can be easily determined by an almost noninvasive method. This can be considered a potential advantage for many practical activities compared with other invasive methods. The concentration dependence curve of pheomelanin (µg/mg) on g_exp‐factor in an ESR spectrum of hair has been designed, which allows the determination of the amount of pheomelanin in hair of any color. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of primordial radionuclide concentrations in UAE groundwater using high-resolution gamma-ray spectrometry

Journal of Radioanalytical and Nuclear Chemistry - Groundwater is the most valuable resource in arid regions, such as UAE. Estimations of natural radionuclide concentrations are important to...     

Biologically Relevant Molecular Transducer with Increased Computing Power and Iterative Abilities

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Challenges and strategies in the preparation of large‐volume polymer‐based monolithic chromatography adsorbents

To date, the number of published reports on the large‐volume preparation of polymer‐based monolithic chromatography adsorbents is still lacking and is of great importance. Many critical factors need to be considered when manufacturing a large‐volume polymer‐based monolith for chromatographic applications. Structural integrity, validity, and repeatability are thought to be the key factors determining the usability of a large‐volume monolith in a separation process. In this review, we focus on problems and solutions pertaining to heat dissipation, pore size distribution, “wall channel” effect, and mechanical strength in monolith preparation. A template‐based method comprising sacrificial and nonsacrificial techniques is possibly the method of choice due to its precise control over the porous structure. However, additional expensive steps are usually required for the template removal. Other strategies in monolith preparation are also discussed.     

Pyrimidoquinazolinophenanthroline Opens Next Chapter in Design of Bridging Ligands for Artificial Photosynthesis**

The synthesis and detailed characterization of a new Ru polypyridine complex containing a heteroditopic bridging ligand with previously unexplored metal-metal distances is presented. Due to the twisted geometry of the novel ligand, the resultant division of the ligand in two distinct subunits leads to steady state as well as excited state properties of the corresponding mononuclear Ru(II) polypyridine complex resembling those of prototype [Ru(bpy)₃]²⁺ (bpy=2,2'-bipyridine). The localization of the initially optically excited and the nature of the long-lived excited states on the Ru-facing ligand spheres is evaluated by resonance Raman and fs-TA spectroscopy, respectively, and supported by DFT and TDDFT calculations. Coordination of a second metal (Zn or Rh) to the available bis-pyrimidyl-like coordination sphere strongly influences the frontier orbitals, apparent by, for example, luminescence quenching. Thus, the new bridging ligand motif offers electronic properties, which can be adjusted by the nature of the second metal center. Using the heterodinuclear Ru−Rh complex, visible light-driven reduction of NAD⁺ to NADH was achieved, highlighting the potential of this system for photocatalytic applications.     

Adsorption-Inhibition of Clathrate Hydrates by Self-Assembled Nanostructures

The mechanism by which safranine O (SFO), an ice growth inhibitor, halts the growth of single crystal tetrahydrofuran (THF) clathrate hydrates was explored using microfluidics coupled with cold stages and fluorescence microscopy. THF hydrates grown in SFO solutions exhibited morphology changes and were shaped as truncated octahedrons or hexagons. Fluorescence microscopy and microfluidics demonstrated that SFO binds to the surface of THF hydrates on specific crystal planes. Cryo-TEM experiments of aqueous solutions containing millimolar concentrations of SFO exhibited the formation of bilayered lamellae with an average thickness of 4.2±0.2 nm covering several μm². Altogether, these results indicate that SFO forms supramolecular lamellae in solution, which might bind to the surface of the hydrate and inhibit further growth. As an ice and hydrate inhibitor, SFO may bind to the surface of these crystals via ordered water molecules near its amine and methyl groups, similar to some antifreeze proteins.     

Torsional control by intense pulses

We generalize the concepts of alignment and 3D alignment by moderately intense laser pulses to control both the overall rotations and the torsional motions of polyatomic molecules. Torsional control is applied to manipulate charge transfer events, hence introducing a potential route to light controlled molecular switches. Potential applications in areas such as molecular assembly, molecular spectroscopies, energy transfer, and molecule-based junctions are envisioned.     

Structural elucidation of V‐type nerve agents by liquid chromatography/electrospray ionization mass spectrometry

V‐nerve agents present information‐poor spectra, both in GC‐EI‐MS and LC‐ESI‐MS/MS, with dominant fragments/product ions corresponding to the amine‐containing residue. Hence, derivatives/isomers with the same amine residue exhibit similar mass spectral patterns, leading to ambiguity in the phosphonate structure. We present a simple approach for their structural elucidation based on two complementary experiments: ESI‐MS/MS of the original compound, which provides information about the amine moiety, and ESI‐MS/MS of the phosphonic acid hydrolysis products generated by N‐iodosuccinimide, which provides ions' characteristic of the phosphonate structure. This approach enables the structural elucidation of the original V‐agents with a higher degree of certainty.     

Two helium atoms inside fullerenes: probing the internal magnetic field in C60(6-) and C70(6-)

A 3He NMR resonance of C606- containing He is assigned to He2@C606-, thus showing that C60 can also accommodate two helium atoms. The ratio of the di-helium compound relative to the mono- is 1:200, 10 times lower than the equivalent counterpart of C70. The 3He NMR chemical shift of He2@C606- is 0.093 ppm downfield from the already known resonance of He@C606-. In the reduced endohedral mono- and di-helium C70, the 3He NMR chemical shift of He2@C706- is 0.154 ppm upfield from the peak of He@C706-.