A note on the lower-bound nature of the linearized CPMET

It is shown by a simple demonstration that the energy calculated from the linearized version of the coupled-pair many-electron theory (L-CPMET) of ?í?ek is the same as that would be obtained from the lower-bound equation of the wave operator for pair correlations as derived by Goscinski and Sinano?lu. A possible extension of L-CPMET retaining the lower-bound character is also indicated.     

Calculation of chemisorption and absorption induced surface segregation

Using a pair bond type model for the interatomic interactions, we determine surface segregation on clean, H, O and CO covered surfaces of various alloys. Furthermore, we study surface segregation caused by bulk hydrogen absorption. Numerical results are presented for Pd_x Zr_1?x H_y We find, that strong surface segregation may result from chemisorption of O and CO and from absorption of H in the bulk of an alloy.     

On-demand electrochemical release of DNA from gold surfaces

Electrochemical quartz crystal microbalance (EQCM) is used to probe the electrochemically triggered release of nucleic acids from gold surfaces to solutions of physiological pH. The immobilization of nonthiolated DNA onto the gold surface is followed by an electrostatic desorption at -1.0 V (vs. Ag/AgCl). Steady-state frequency signals, corresponding to the removal of 261- and 644-ng/cm2 single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA), respectively, were attained within 75 and 330 s. As expected for electrostatic repulsion, the amount released can be manipulated by tuning the potential. The small nonsteady-state frequency signals observed at lower potentials indicate promise for a sustained DNA release. Applicability to gold ultramicroelectrodes (12.5-microm radius) is demonstrated in connection with voltammetric blocking experiments. We expect that such on-demand electrochemical release would be a useful addition to the arsenal of nonviral gene delivery routes.     

Modulation of the Conformational Space of SARS-CoV-2 RNA Quadruplex RG-1 by Cellular Components and the Amyloidogenic Peptides α-Synuclein and hIAPP

Given the emergence of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), which particularly threatens older people with comorbidities such as diabetes mellitus and dementia, understanding the relationship between Covid-19 and other diseases is an important factor for treatment. Possible targets for medical intervention include G-quadruplexes (G4Qs) and their protein interaction partners. We investigated the stability and conformational space of the RG-1 RNA-G-quadruplex of the SARS-CoV-2 N-gene in the presence of salts, cosolutes, crowders and intrinsically disordered peptides, focusing on α-Synuclein and the human islet amyloid polypeptide, which are involved in Parkinson's disease (PD) and type-II diabetes mellitus (T2DM), respectively. We found that the conformational dynamics of the RG-1 G4Q is strongly affected by the various solution conditions. Further, the amyloidogenic peptides were found to strongly modulate the conformational equilibrium of the RG-1. Considerable changes are observed with respect to their interaction with human telomeric G4Qs, which adopt different topologies. These results may therefore shed more light on the relationship between PD as well as T2DM and the SARS-CoV-2 disease and their molecular underpinnings. Since dysregulation of G4Q formation by rationally designed targeting compounds affects the control of cellular processes, this study should contribute to the development of specific ligands for intervention.     

Gibbs Measures on Mutually Interacting Brownian Paths under Singularities

We are interested in the analysis of Gibbs measures defined on two independent Brownian paths in ?^d interacting through a mutual self‐attraction. This is expressed by the Hamiltonian with two probability measures μ and ν representing the occupation measures of two independent Brownian motions. We will be interested in a class of potentials V that are singular , e.g., Dirac‐ or Coulomb‐type interactions in ?³, or the correlation function of the parabolic Anderson problem with white noise potential. The mutual interaction of the Brownian paths inspires a compactification of the quotient space of orbits of product measures, which is structurally different from the self‐interacting case introduced in [27], owing to the lack of shift‐invariant structure in the mutual interaction. We prove a strong large‐deviation principle for the product measures of two Brownian occupation measures in such a compactification and derive asymptotic path behavior under Gibbs measures on Wiener paths arising from mutually attracting singular interactions. For the spatially smoothened parabolic Anderson model with white noise potential, our analysis allows a direct computation of the annealed Lyapunov exponents, and a strict ordering of them implies the intermittency effect present in the smoothened model. © 2017 Wiley Periodicals, Inc.     

Theoretical and experimental investigations on the formation of air core in a swirl spray atomizing nozzle

Theoretical and experimental studies have been made to investigate the variations of air core diameter, the most important hydrodynamic picture inside a swirl nozzle, with the pertinent guiding parameters like injection condition expressed as the Reynolds number at inlet to the nozzle and the geometrical dimensions of the nozzle, namely, the length and diameter of the swirl chamber, angle of spin chamber and the orifice diameter. The theoretical relations have been established through an approximated analytical solution of the hydrodynamics of flow of a viscous incompressible fluid in a swirl nozzle. A series of experiments have been carried out to support and compare the theoretical results. Finally, it has been recognized that for any nozzle, the air core diameter becomes a direct function of Reynolds number Re _i at inlet to the nozzle only at its lower range and then remains constant. Amongst the nozzle geometrics, the ratio of orifice to swirl chamber diameter D ₂/D ₁ has got the most predominant effect on the air core diameter. An increase in the ratio of orifice to swirl chamber diameter D ₂/D ₁, and in the spin chamber angle 2 and a decrease in the swirl chamber length to diameter ratio L ₁/D ₁ increase the ratio of air core to orifice diameter and vice versa.Nomenclature A _E Area of tangential inlet ports of the nozzle - A ₂ Area of the orifice - a Air core radius - D ₁ Swirl chamber diameter - D ₂ Orifice diameter - d ₂ Air core diameter - E A nondimensional parameter defined by equation (14) - E _R A nondimensional parameter defined by equation (33) - L ₁ Length of the swirl chamber - P Static pressure - P _b Back pressure of the nozzle - Q Volume flow rate - R Radius vector or the longitudinal co-ordinate with respect to spherical co-ordinate system (figure 3) - R ₁ Radius of the swirl chamber - R ₂ Radius of the orifice - Re _i Reynolds number at inlet to the nozzle - R _z Radius of the nozzle at any section - r Radial distance from the nozzle axis - U Longitudinal component of velocity with respect to spherical co-ordinate system (figure 3) - V Component of velocity in the axial plane perpendicular to R as defined in (figure 3) - V _r Radial velocity component - V _z Axial velocity component - V _Ø Tangential velocity component - Average tangential velocity at inlet to the nozzle - w Component of velocity perpendicular to axial plane with respect to the spherical co-ordinate as defined in figure 3 - z Distance along the nozzle axis from its inlet plane - Half of the spin chamber angle - Boundary layer thickness - ₂ Boundary layer thickness at the orifice - Angle which a radius vector according to the system of spherical coordinates (figure 3) makes with the nozzle axis - Dynamic viscosity - Kinematic viscosity - Density - Ø Running co-ordinate in the azimuthal direction with respect to the cylindrical polar co-ordinate system as shown in figure 3 - Circulation constant     

Computational Insights into the Role of External and Local Electric Fields in Macrocyclic Chemical and Biological Systems

The investigation of the role of the electric field in systems of widespread interest employing computational techniques is an emerging area of research. The outcome of applying an oriented external electric field (OEEF) on the geometric and electronic properties of the chemically unique π-conjugated cyclic carbon ring compounds has been explored with density functional theory (DFT). Distinct changes in the structural and electronic features of such ring compounds are observed upon the application of OEEFs. Importantly, the calculations indicate that a mixed aliphatic-aromatic conjugated ring converts from a singlet to a triplet after the application of an OEEF, suggesting potential applications in optoelectronics for such molecules, without the need for photochemically induced change in the spin state. Furthermore, the influence of built-in local electric fields (LEFs) present in naturally occurring macrocyclic systems such as valinomycin has also been explored. Static and ab initio molecular dynamics (AIMD) calculations indicate that LEFs are the primary driving factor in determining the energetically favoured position of counter anions such as chloride (Cl⁻) in the potassium (K⁺) and sodium (Na⁺) coordinated valinomycin macrocycle structures: they exist inside the cage in the case of K⁺ sequestration by valinomycin and outside for Na⁺. This divergence has been proposed to be the determining factor for the selectivity of the valinomycin macrocycle for binding a K⁺ cation over Na⁺.     

Efficient Solid‐State Light‐Emitting CuCdS Nanocrystals Synthesized in Air

Semiconductor nanocrystals (NCs) possess high photoluminescence (PL) typically in the solution phase. In contrary, PL rapidly quenches in the solid state. Efficient solid state luminescence can be achieved by inducing a large Stokes shift. Here we report on a novel synthesis of compositionally controlled CuCdS NCs in air avoiding the usual complexity of using inert atmosphere. These NCs show long‐range color tunability over the entire visible range with a remarkable Stokes shift up to about 1.25 eV. Overcoating the NCs leads to a high solid‐state PL quantum yield (QY) of ca. 55 % measured by using an integrating sphere. Unique charge carrier recombination mechanisms have been recognized from the NCs, which are correlated to the internal NC structure probed by using extended X‐ray absorption fine structure (EXAFS) spectroscopy. EXAFS measurements show a Cu‐rich surface and Cd‐rich interior with 46 % Cu^I being randomly distributed within 84 % of the NC volume creating additional transition states for PL. Color‐tunable solid‐state luminescence remains stable in air enabling fabrication of light‐emitting diodes (LEDs).