Theoretical analysis of the structural and electronic properties of metalloporphyrin pi-cation radicals

A method for analyzing the A(1u)/A(2u) contents of metalloporphyrin pi-cation radicals is developed and applied to a series of unsubstituted planar metalloporphines (MPs) (M=Cr, Mn, Fe, Co, Ni, Cu, and Zn). The structures and electronic properties of the MPs and their cation radicals were calculated by density functional theory (DFT) and subsequently analyzed. It was found that the MPs with small core sizes have a tendency to form A(1u)-type radicals, while the MPs with large core size have a preference for an A(2u)-type. Neither of these pure-state species, however, is stable under the D(4)(h) symmetry, and both radical cation types are subject to pseudo-Jahn-Teller (pJT) distortion. The pJT distortion leads to structures with lower symmetry and states that have mixed character with respect to the A(1u) and A(2u) components. The degree of mixing could be estimated by employing orbital projection technique or a complementary spin density decomposition. Both techniques produce very similar results, pointing out that the frontier orbital, which becomes empty upon electron removal, plays a critical role in determining electronic properties.     

On the efficiency of bile salt for stable suspension and isolation of single-walled carbon nanotubes—spectroscopic and microscopic investigations

In this contribution we present a systematic study on the dispersion of SWCNTs in a water-based solution of biocompatible detergent: sodium deoxycholate (DOC). By avoiding harsh chemical conditions, which are known to damage nanotubes structure, a stable SWCNTs suspension was created. Long term stirring of the solution led to preparation of a stable transparent solution, containing well-dispersed isolated SWCNTs. The as-prepared dispersion remained stable and clear for two months. Optical absorption spectroscopy was employed to measure SWCNTs suspension stability. Nanotube aggregation was evaluated through the tangential mode (G mode) present in the Raman spectrum. High-resolution transmission electron microscopy was employed to observe the mechanism of debundling process.     

Graph algorithms for DNA sequencing – origins,current models and the future

With the ubiquitous presence of next-generation sequencing in modern biological, genetic, pharmaceutical and medical research, not everyone pays attention to the underlying computational methods. Even fewer researchers know what were the origins of the current models for DNA assembly. We present original graph models used in DNA sequencing by hybridization, discuss their properties and connections between them. We also explain how these graph models evolved to adapt to the characteristics of next-generation sequencing. Moreover, we present a practical comparison of state-of-the-art DNA de novo assembly tools representing these transformed models, i.e. overlap and decomposition-based graphs. Even though the competition is tough, some assemblers perform better and certainly large differences may be observed in hardware resources utilization. Finally, we outline the most important trends in the sequencing field, and try to predict their impact on the computational models in the future.     

Regular Boundary Points and Exit Distributions for Parabolic Differential Operators

We show that the regularity of a boundary point for a parabolic differential operator in divergence form is under some geometric assumptions equivalent to the property that the density of the exit distribution for a time reversed process vanishes at that point. We give regularity and irregularity criterions for equations with variable coefficients. Thus, the known result on the Fulks measure that states that the density with respect to the Lebesgue measure vanishes at the point opposite to the center of the heat ball (see Fulks (Proc. Am. Math. Soc. 17, 6–11 1966)) can be extended to exit distributions for more general regions and parabolic differential operators.     

Relaxation and decoherence of orbital and spin degrees of freedom in quantum dots

The phonon induced mechanisms of relaxation/decoherence in quantum dots are analysed. A non-perturbative technique - a modification of the Davydov transformation appropriate to the localised particles is applied for solving the electron-phonon eigenvalue problem in a quantum dot at magnetic field presence. The decay rates for polaron relaxation via the anharmonicity induced channel are analysed in details. In particular, it is indicated that previous, of perturbative type, estimations of the anharminicity induced relaxation rates were too severe and after including the coherence effects they are of, at least, one order longer. The process of exciton dressing with phonons is also analysed as the unavoidable source of picosecond scale decoherence in optically driven nanostructures. A break-down of an instant Pauli spin blocking mechanism and a large enhancement of the Fröhlich constant for confined electrons are also addressed.     

The Poincaré Map of Randomly Perturbed Periodic Motion

A system of autonomous differential equations with a stable limit cycle and perturbed by small white noise is analyzed in this work. In the vicinity of the limit cycle of the unperturbed deterministic system, we define, construct, and analyze the Poincaré map of the randomly perturbed periodic motion. We show that the time of the first exit from a small neighborhood of the fixed point of the map, which corresponds to the unperturbed periodic orbit, is well approximated by the geometric distribution. The parameter of the geometric distribution tends to zero together with the noise intensity. Therefore, our result can be interpreted as an estimate of the stability of periodic motion to random perturbations. In addition, we show that the geometric distribution of the first exit times translates into statistical properties of solutions of important differential equation models in applications. To this end, we demonstrate three distinct examples from mathematical neuroscience featuring complex oscillatory patterns characterized by the geometric distribution. We show that in each of these models the statistical properties of emerging oscillations are fully explained by the general properties of randomly perturbed periodic motions identified in this paper.     

Application of multiple quench parameters for confirmation of radionuclide identity in radioanalytical quality control

Journal of Radioanalytical and Nuclear Chemistry - Robust and reliable radiochemical analysis is the key factor in the appropriate disposal and management of radioactive wastes arising from the...     

Correction to: Foreword to the memorial issue for Professor Roberto Marassi

Journal of Solid State Electrochemistry -     

Late-Stage Functionalization by Chan–Lam Amination: Rapid Access to Potent and Selective Integrin Inhibitors

A late-stage functionalization of the aromatic ring in amino acid derivatives is described. The key step is a copper-catalysed diversification of a boronate ester by amination (Chan–Lam reaction) that can be carried out on a complex β-aryl-β-amino acid scaffold. This not only considerably extends the substrate scope of amination partners, but also delivers an array of potent and selective integrin inhibitors as potential treatment agents of idiopathic pulmonary fibrosis (IPF). This versatile chemical strategy, which is amenable to high-throughput-array protocols, allows the installation of pharmaceutically valuable heteroaromatic fragments at a late stage by direct coupling to NH heterocycles, leading to compounds with drug-like attributes. It thus constitutes a useful addition to the medicinal chemist's repertoire.     

The influence of compression conditions on the peculiarities of self-propagating exothermal reaction in Al–Ni powder reactive materials

The paper deals with the effect of the compression conditions on the propagation front velocity of exothermal reaction and the specific heat release in Al–Ni powder reactive materials with mean particle sizes of 70–110 nm. It was shown that the velocity increases from 2.7 to 8 cm s^?1 and comes to saturation with the lowering of the porosity (η) from 0.91 to 0.34, while the dependence of the specific heat release has its maximum for η?=?0.5. The results of the X-ray diffraction analysis obtained in situ during the sample heating suggest that the sequence of phase transformations in the system does not depend on the porosity. In all cases, first in the temperature range of ~?500–540 °C the NiAl compound is formed. With the further heating up to ~?640 °C, the Ni₃Al, Ni₂Al₃ and NiAl₃ compounds are additionally formed. The calculation of kinetic parameters was performed using the obtained curves of the differential scanning calorimetry: activation energy, pre-exponential factor and reaction model. The comparison of the calculated results and the scanning electron microscopy data has shown that such behavior of the Al–Ni system with the porosity lowering occurs due to the growth of the transformation degree and is associated with the presence in the final powder mixture of mutually non-contacting Al and Ni agglomerates with the dimensions of over 10 μm.