REE Spectral Lines for the Determination of Excitation Temperature in Analytical Plasmas

The spectra of rare earth elements (REE) have been investigated to select thermometric species for spectroscopic diagnostic of analytical plasmas. Groups of lines of Y II, La II, Eu II and Yb II were found appropriate for the determination of ionic excitation temperature in argon wall-stabilized plasma arc (WSA) and inductively coupled plasma (ICP). Boltzman plots with excellent Fitting to straight lines were obtained. Temperature values deduced with the different groups of spectral lines agree with each other as well as with that obtained with the most familiarly used Ti II lines.

     

Development and Validation of a Stability-Indicating High-Performance Thin-Layer Chromatographic Method for Determination of Pyridostigmine Bromide in the Presence of Its Alkaline-Induced Degradation Product

JPC – Journal of Planar Chromatography – Modern TLC - A validated, sensitive, and highly selective stability-indicating high-performance thin-layer chromatographic (HPTLC) method has...     

Polaronic and charge ordering effects in Pr 0.5 Sr 0.5 Mn 1− x Fe x O 3

In this work we report the results of X-ray diffraction and Mössbauer spectroscopy for the systems Pr_0.5Sr_0.5Mn_1???x Fe _x O₃ (with x?=?0.05, 0.10, 0.15, 0.20, 0.25, 0.30). XRD patterns indicated that all samples were single phase with slightly distorted orthorhombic symmetry. Room temperature Mössbauer spectra are all quadrupole split, indicating paramagnetic relaxation of the Fe moment for all values of Fe concentrations. The spectra are fitted with two doublet components associated with Fe^3?+? ions in octahedral sites with different distortions. Mössbauer spectra recorded at liquid nitrogen temperature for this system also indicate paramagnetic relaxation of the Fe moments down to liquid nitrogen temperature (LNT). In these spectra a third quadrupole component with quadrupole splitting close to zero develops. This component is associated with the delocalization of the charge carriers and the consequent disappearance of lattice distortions produced by the polaronic effect at room temperature. The component with the high quadrupole splitting (0.81 to 1.07 mm/s) results from Jahn–Teller distortion as a consequence of charge ordering transition at low temperature.     

Notes on the convergence order of gradient schemes for time fractional differential equations

We apply the GDM (Gradient Discretization Method), developed recently, as discretization in space to time-fractional diffusion and diffusion-wave equations with a fractional derivative of Caputo type in any space dimension.In the case of time-fractional diffusion equations, we establish an implicit scheme, and we prove an $L^{\infty }(L^2)$-error estimate. A similar result in a discrete $L^{\infty }(H_0^1)$–norm is also stated.To construct the numerical scheme for the time-fractional diffusion-wave equation, we write the equation in the form of a system of two low-order equations. We state an a prior estimate result that helps us to derive error estimates in discrete semi-norms of $L^{\infty }(H^1)$ and $H^1(L^2)$. The convergence is unconditional. Another gradient scheme is also suggested. We state its convergence results, which improve the convergence order proved recently for a SUSHI scheme.These results hold then for all the schemes within the framework of GDM: conforming and nonconforming finite element, mixed finite element, hybrid mixed mimetic family, some Multi-Point Flux approximation finite volume schemes, and some discontinuous Galerkin schemes.     

Combinatorial invariance of Kazhdan–Lusztig–Vogan polynomials for fixed point free involutions

When \(\mathrm {Sp}(2n,\mathbb {C})\) acts on the flag variety of \(\mathrm {SL}(2n,\mathbb {C})\), the orbits are in bijection with fixed point free involutions in the symmetric group \(S_{2n}\). In this case, the associated Kazhdan–Lusztig–Vogan polynomials \(P_{v,u}\) can be indexed by pairs of fixed point free involutions \(v\ge u\), where \(\ge \) denotes the Bruhat order on \(S_{2n}\). We prove that these polynomials are combinatorial invariants in the sense that if \(f:[u,w_0]\rightarrow [u',w_0]\) is a poset isomorphism of upper intervals in the Bruhat order on fixed point free involutions, then \(P_{v,u} = P_{f(v),u'}\) for all \(v\ge u\).     

Density functional theory study of pyrrole adsorption on Mo(110)

The objective of the present study is to identify possible adsorption configurations of pyrrole on Mo(110) using density functional theory (DFT) calculations. Several adsorption configurations were studied including pyrrole and pyrrolyl adsorption as parallel, perpendicular, and tilted adsorption modes relative to the Mo(110) surface plane. Based on the DFT calculations, pyrrole is suggested to adsorb in a parallel mode with respect to the Mo(110) surface through its pi-orbital as mu3,eta(5)-Pyr-0 degrees with an adsorption energy of -28.7 to -31.5 kcal mol(-1). The possibility of a coexisting mode where pyrrole adsorbs on the surface with a slightly tilted molecular plane as mu3,eta(4)(N,C2,C3,C4)-Pyr-5 degrees is also likely to occur, particularly at higher pyrrole coverages. The slightly tilted configuration is suggested to arise from the lateral interactions of adsorbed pyrrole on Mo(110), and not the result of a phase transformation on the surface since this requires a relatively high activation energy as indicated by additional linear synchronous transit (LST)/quadratic synchronous transit (QST) calculations. Both adsorption geometries bond to three surface Mo atoms, and Mo(110) did not promote hydrogen abstraction. Pyrrolyl adsorption on Mo(110) is energetically possible, but unlikely to occur because gas-phase hydrogen has not been previously experimentally observed as a pyrrole decomposition product on Mo(110).     

Spectrophotometric Determination of Some Fluoroquinolone Antibacterials by Ion‐pair Complex Formation with Cobalt (II) Tetrathiocyanate

A new simple extractive spectrophotometric method has been developed for the determination of levofloxacin (I), norfloxacin (II), and ciprofloxacin (III) in pure form and tablets. The method is based on the formation of blue‐colored ion‐pair associates between the drugs and the inorganic complex, cobalt (II) thiocyanate, at pH 2.5. Those ion‐pair associates are readily extracted into an n‐butanol‐dichloromethane solvent mixture (3.5:6.5) and determined spectrophotometrically at 623 nm. The concentration range is 20–240 μg mL^?1 for the three studied drugs. The proposed method was successfully applied to determine these drugs in their tablet formulations, and the results are in good agreement with those obtained by the reference methods.