WKB approach to calculating the lifetime of quasistationary states

A novel WKB approach to calculating the lifetime of quasistationary states in the potential wells of the form V(x)=P(x)-muQ(x), where P(x) is the radial part of the potential for the spherically symmetric harmonic oscillator or the hydrogen atom and Q(x) is a polynomial, is suggested. In this approach, the usual explicit procedure of the asymptotic matching of the perturbative and WKB wave functions is avoided and a simple formula for the imaginary part of the energy is found. The leading and the first correction terms for the imaginary part of the energy and the related lifetime are analytically calculated.     

Large-Order Strong Coupling Perturbation Coefficients for Anharmonic Oscillators

A large-order formula for the perturbation coefficients of the strong-couplingperturbation expansion for anharmonic oscillators with Hamiltonian H = p ² +x ² + x ^2m is derived and parameters in thisformula are determined for the ground and first excited states of the quartic,sextic, octic, and decadic oscillators (m = 2, 3, 4, 5).     

Interplay of the Staggered and Three-Body Interaction Potentials on the Quantum Phases of a Spin-1 Ultracold Atom in an Optical Lattice

The interplay of the staggered and the three-body interaction potentials on the quantum phases of a spin-1 Bose Hubbard model using a mean field approximation (MFA) is studied. In the antiferromagnetic (AF) case, a smaller value of the staggered potential (SP) results in the charge and the spin density wave ordering along with the Mott insulator (MI) and the staggered superfluid (SSF) phases. While the competition between two types of the potential leads to the stabilization of the higher order MI and charge density wave (CDW) phases with increasing three-body interaction strength. Further, the spin eigenvalue and nematic order parameters are calculated to scrutinize the spin singlet-nematic formation in the MI and the CDW phases and spin population fractions to analyze the nature of the SSF phase. A signature of the spin density wave (SDW) pattern is also observed in the gapped phase lobes. In case of a purely three-body interaction, the third and higher order insulating lobes become dominant with increasing staggered potential strength. Subsequently, all MFA phase diagrams are then nicely corroborated with the analytical results obtained using a perturbative expansion corresponding to the AF and ferromagnetic cases.     

Synthesis,spectral characterization and bioactivity evaluation of novel α-aminophosphonates

A facile synthesis of novel α-aminophosphonates 5a-j was accomplished by condensation of imines (3a-j) with diethyl phosphite (4) in ethanol at 50–60°C using easily recoverable and reusable catalyst, tetramethyl guanidine (TMG) via pudovik reaction in high yields. All the title compounds were characterized by spectral and elemental analysis. They were further screened for their abilities towards in vitro antibacterial, antifungal and antioxidant activities. The compounds 5g, 5d, 5f exhibited good antibacterial and antifungal activities compared to the standard bactericide, Penicillin and fungicide, Griseofulvin, respectively. The compounds 5h, 5i, 5g, and 5c exhibited good antioxidant activity compared to the standard ascorbic acid.     

Synthesis,crystal and molecular structures of 1D and 2D supramers of copper(II) with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-{bis(pyridin-2-yl) benzylidene}butane-1,4-diamine

Reaction of copper(II) perchlorate with N,N′-{bis(pyridin-2-yl)benzylidene}butane-1,4-diamine (bpbd) yielded monoclinic crystals of bluish green [Cu(bpbd)(ClO₄)]ClO₄ (1), and a similar reaction in presence of azide anion, N₃ ^? formed monoclinic crystals of dark green [Cu(bpbd)(N₃)]₂ClO₄ (2). Crystal data for 1: space group P21/c, Z=4, a=17.3968(4) Å, b=9.3182(2) Å, c=17.6794(4) Å, β=102.149(1)°. The geometry around Cu(II) centre is distorted square pyramidal with axial site occupied by O atom of perchlorate and in plane Cu is bonded to four N atoms of the organic ligand. The intermolecular C–H...π stacking in 1 forms a zigzag chain (1D) supramer. Crystal data for 2: space group C2/c, Z=4, a=22.3109(4) Å, b=17.7832(3) Å, c=14.3389(2) Å, β=92.553(1)°. In dinuclear 2, Cu(II) has tetragonally distorted octahedral geometry coordinated by four N atoms of bpbd, with the fifth and sixth positions occupied by N atoms of two end-on bridging azides. The π...π interaction leads to a two dimensional (2D) sheet within which the counter anions are embedded. Both the compounds 1 and 2 show simple paramagnetism. Cyclic voltammetry and fluorescence spectra are also reported.     

Structural analysis of arylsulfonamide-based carboxylic acid derivatives: a QSAR study to identify the structural contributors toward their MMP-9 inhibition

Structural Chemistry - Matrix metalloproteinases (MMPs) are a group of endopeptidases renowned for their ability to degrade the extracellular matrix (ECM) and contribute in different physiological...     

Long-lasting hydrophilicity on nanostructured Si-incorporated diamond-like carbon films

We investigated the long-lasting hydrophilic behavior of a Si-incorporated diamond-like carbon (Si-DLC) film by varying the Si fraction in DLC matrix through oxygen and nitrogen plasma surface treatments. The wetting behavior of the water droplets on the pure DLC and Si-DLC with the nitrogen or oxygen plasma treatment revealed that the Si element in the oxygen-plasma-treated Si-DLC films played a major role in maintaining a hydrophilic wetting angle of <10° for 20 days in ambient air. The nanostructured patterns with a roughness of ～10 nm evolved because of the selective etching of the carbon matrix by the oxygen plasma in the Si-DLC film, where the chemical component of the Si-Ox bond was enriched on the top of the nanopatterns and remained for over 20 days.     

Application of desymmetrization protocol for the formal total synthesis of emericellamide B

A highly convergent formal total synthesis of emericellamide B, a 19-membered antibacterial depsipeptide is described. The key feature of the strategy is the generation of four stereogenic centers from a bicyclic precursor via desymmetrization technique and utilization for emericellamide B and related natural product synthesis.     

Evolution of optical pulses in the presence of third-order dispersion

We model the propagation of femtosecond pulses through optical fibres by a nonlinear Schrödinger (NLS) equation involving a perturbing term arising due to third-order dispersion in the medium. The perturbative effect of this higher-order dispersion causes the usual NLS soliton to emit a radiation field. As a result, the given initial pulse propagating through the fibre exhibits nonsolitonic behaviour. We make use of a variational method to demonstrate how an initial pulse by the interaction with the emitted radiation can evolve into a soliton. We also demonstrate that the effect of interaction between the initial pulse and radiation field can be accounted for by including, in the evolution equation, terms associated with self-steepening and stimulated Raman scattering that characterize the optical medium.     

Effects of three-body atomic interaction and optical lattice on solitons in quasi-one-dimensional Bose-Einstein condensate

We make use of a coordinate-free approach to implement Vakhitov-Kolokolov criterion for stability analysis in order to study the effects of three-body atomic recombination and lattice potential on the matter-wave bright solitons formed in Bose-Einstein condensates. We analytically demonstrate that (i) the critical number of atoms in a stable BEC soliton is just half the number of atoms in a marginally stable Townes-like soliton and (ii) an additive optical lattice potential further reduces this number by a factor of √1 − bg ₃ with g ₃ the coupling constant of the lattice potential and b = 0.7301.