Microstructural,chemical bonding,stress development and charge storage characteristics of Ge nanocrystals embedded in hafnium oxide

We have grown Ge nanocrystals (NCs) (4.0–9.0 nm in diameter) embedded in high-k HfO₂ matrix for applications in floating gate memory devices. X-ray photoelectron spectroscopy has been used to probe the local chemical bonding of Ge NCs. The analysis of Ge–Ge phonon vibration using Raman spectroscopy has shown the formation of compressively stressed Ge NCs in HfO₂ matrix. Frequency dependent electrical properties of HfO₂/Ge-NCs in HfO₂/HfO₂ sandwich structures have been studied. An anticlockwise hysteresis in the capacitance–voltage characteristics suggests electron injection and trapping in embedded Ge NCs. The role of interface states and deep traps in the devices has been thoroughly examined and has been shown to be negligible on the overall device performance.     

Multireference perturbation theory with improved virtual orbitals for radicals: More degeneracies,more problems

IVO-SSMRPT is an affordable and accurate type of state-specific multireference perturbation (SSMRPT) theory that adds dynamic correlation energy to improved virtual orbital (IVO) complete active space configuration interaction (CASCI) wave functions using a single-root parametrization of multi-root Hilbert-space ansatz. We applied it to many chemically important di- and tri-radicals to analyze the geometries and electronic properties of spectroscopic interest for both closed- and open-shell singlet- and nonsinglet ground as well as excited states. We observed that IVO-SSMRPT identifies optimized geometries, splitting between multiplets and frequencies for several radicals that are similar to those displayed by current generation state-of-the-art methods but with admiringly decreased computational effort. This study illustrates the importance of having an accurate treatment of both nondynamical and dynamical correlation effects when examining multiradical species. Chemically and spectroscopically relevant answers can be obtained using our computationally tractable method. Our method will be a serviceable avenue for portraying open-shell interactions in other radicals.     

The Hexameric Resorcinarene Capsule at Work: Supramolecular Catalysis in Confined Spaces

The hexameric resorcinarene capsule reported by Atwood in 1997 is able to act as a supramolecular catalyst. Its inner cavity provides a unique environment, in which organic reactions can be efficiently catalyzed, thanks to the confinement effect of the substrates. In addition, different stereo- and regiochemical outcomes can be observed with respect to reactions in the bulk solvent. The hexameric capsule shows some catalytic features reminiscent of natural enzymes. In particular, highlights of the capsule discussed herein include 1) its ability to recognize the substrates (substrate selectivity), 2) the possibility of stabilizing the transition states and intermediates through secondary interactions, 3) an inherent Brønsted acidity, and 4) its ability to act as a hydrogen-bond catalyst. In addition, it is also shown how the catalytic activity of the hexameric capsule can be modulated in the presence of competitive alkylammonium guests, which show high affinities for its internal cavity. These aspects are discussed through a critical examination of data reported in the literature in recent years.     

NiII-ATCUN-Catalyzed Tyrosine Nitration in the Presence of Nitrite and Sulfite

The nitration of tyrosine residues in proteins represents a specific footprint of the formation of reactive nitrogen species (RNS) in vivo. Here, the fusion product of orange protein (ATCUN-ORP) was used as an in vitro model system containing an amino terminal Cu(II)- and Ni(II)-binding motif (ATCUN) tag at the N-terminus and a native tyrosine residue in the metal-cofactor-binding region for the formation of 3-NO₂-Tyr (3-NT). It is shown that Ni^II-ATCUN unusually performs nitration of tyrosine at physiological pH in the presence of the NO₂⁻/SO₃²⁻/O₂ system, which is revealed by a characteristic absorbance band at 430 nm in basic medium and 350 nm in acidic medium (fingerprint of 3-NT). Kinetics studies showed that the formation of 3-NT depends on sulfite concentration over nitrite concentration suggesting key intermediate products, identified as oxysulfur radicals, which are detected by spin-trap EPR study by using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). This study describes a new route in the formation of 3-NT, which is proposed to be linked with the sulfur metabolism pathway associated with the progression of disease occurrence in vivo.     

An Experimental-Numerical Hybrid Method for Elastic Contact Problems*

ABSTRACT

An experimental-numerical hybrid technique for determining the contact stress distribution between two elastic bodies having both frictionless as well as bonded contact is discussed in this paper. The hybrid method makes use of experimental data collected at a section far from the contact surface and the numerically generated influence coefficients, in terms of the applied unit normal and shear stresses. The experimental data, i.e., the differences in normal stresses and the shear stress, are obtained using photoelastic analysis for the examples illustrated in this paper. When substituted into equations corresponding to the unit normal and shear stress applied in the contact region, this results in a set of algebraic equations which, when solved, allow the contact stress distribution to be obtained. This method is illustrated with examples involving simple and complex geometries of the contacting bodies.     

Fluid–triangular solid phase transitions in a system of two-dimensional nematic quadrupoles

Density functional theory of freezing is used to study the phase transitions in a system of spherical colloidal particles dispersed in nematic host confined to two dimensions. We have considered both the one-component and two-component systems of the colloidal dispersions. Particles are assumed to interact via director distortion-mediated purely repulsive potential which scales as the fifth power of the inverse interparticle separation. The pair correlation functions needed as input information in the density functional theory are calculated by solving Roger–Young integral equation theory. In one-component system, a triangular crystalline phase is found to be stable. On the other hand, considering the freezing of the fluid phase of the binary mixture into a substitutionally disordered triangular solid, the temperature–composition phase diagram is found to have spindle shape for the ratio of quadrupole moment of the particles of the components being 0.9 and 0.8. The phase diagram changes to an azeotrope at a ratio 0.7. The results are verifiable in real-space experiments on nematic quadrupoles confined to a two-dimensional plane.     

Detection of Hg2+ ion using highly selective fluorescent chemosensor in real water sample and in-vitro cell study upon breast adenocarcinoma (MCF-7)

A novel rhodamine-based chemosensor (R) was designed and synthesised for selective recognition of Hg²⁺ ion in real water samples collected from different places. The chemosensor was prepared in green condition with high yield. The selectivity of R was examined with various metal ions, among which only Hg²⁺ was identified selectively with off–on mechanism along with enhancement of fluorescence. Metal ions recognition has been carried out using UV–vis and fluorescence studies taking µM concentration of chemosensor R in HEPES buffer. The detection limit of R was calculated and found to be 4.4 × 10^–9 M. Quantum chemical (DFT) calculation was carried out in order to acquire knowledge about the stability of R in presence of Hg²⁺ ions. Cell viability and fluorescence microscopic experiments showed R as cytocompatible and can be used as a fluorescent probe for detecting Hg²⁺ in living cells.     

Suppression of the Verwey Transition by Charge Trapping

The Verwey transition in Fe₃O₄ nanoparticles with a mean diameter of 6.3 nm is suppressed after capping the particles with a 3.5 nm thick shell of SiO₂. By X‐ray absorption spectroscopy and its associated X‐ray magnetic circular dichroism this suppression can be correlated to localized Fe²⁺ states and a reduced double exchange visible in different site‐specific magnetization behavior in high magnetic fields. The results are discussed in terms of charge trapping at defects in the Fe₃O₄/ SiO₂ interface and the consequent difficulties in the formation of the common phases of Fe₃O₄. By comparison to X‐ray absorption spectra of bare Fe₃O₄ nanoparticles in course of the Verwey transition, particular changes in the spectral shape could be correlated to changes in the number of unoccupied d states for Fe ions at different lattice sites. These findings are supported by density functional theory calculations.     

Evolution equation for short surface waves on water of finite depth

We address the question of determining the evolution equation for surface waves propagating in water whose depth is much larger than the typical wavelength of the surface disturbance. We avoid making the usual approximation of supposing the evolution to be given in the form of a modulated wave-packet. We treat the problem by means of a conformal transformation allowing to explicitly find the Dirichlet-to-Neumann operator for the problem together with asymptotic expansions in parameters measuring the nonlinearity and depth. This allows us to obtain an equation in physical variables valid in the weakly nonlinear, deep-water regime. The equation is an integro-differential equation, which reduces to known cases for infinite depth. We discuss solutions in a perturbative setting and show that the evolution equation describes Stokes-like waves.     

A polymerization-depolymerization model for generation of contractile force during bacterial cell division

We have investigated the pressure-induced phase transition of NiO and other structural properties using three-body potential approach. NiO undergoes phase transition from B1 (rocksalt) to B2 (CsCl) structure associated with a sudden collapse in volume showing first-order phase transition. A theoretical study of high pressure phase transition and elastic behaviour in transition metal compounds using a three-body potential caused by the electron shell deformation of the overlapping ion was carried out. The phase transition pressure and other properties predicted by our model is closer to the phase transition pressure predicted by Eto et al.