Three-dimensional polarization control in microscopy

We propose an approach to optical microscopy that enables full control over the three-dimensional polarization vector at the focal spot of a high-numerical-aperture lens. The input field to the lens is linearly polarized and no polarization optics are needed. This technique utilizes the azimuthal spatial degree of freedom of the input field. We find that only a small set of low-order azimuthal spatial harmonics contributes to the focused field on axis, and a simple transformation exists between the linear vector space of these harmonics and the three-dimensional polarization-vector space. Controlling the relative complex weights of these azimuthal harmonics produces any desired three-dimensional state of polarization.     

Remarks on pseudo-valuation rings

A prime ideal P of a ring A is said to be a strongly prime ideal if aP and bA are comparable for all a,b ε A. We shall say that a ring A is a pseudo-valuation ring (PVR) if each prime ideal of A is a strongly prime ideal. We show that if A is a PVR with maximal ideal M, then every overring of A is a PVR if and only if M is a maximal ideal of every overring of M that does not contain the reciprocal’of any element of M.We show that if R is an atomic domain and a PVD, then dim(R) ≤ 1. We show that if R is a PVD and a prime ideal of R is finitely generated, then every overring of R is a PVD. We give a characterization of an atomic PVD in terms of the concept of half-factorial domain.     

Mixed thioalkyl-azoimine (SNN′)/α-diimine–ruthenium complexes: synthesis,characterization, DFT calculations,crystal structure and application as pre-catalysts for hydrogenation of acetophenone

Transition Metal Chemistry - Eight ruthenium complexes having thioalkyl-azoimine (SNN) ligands of two general types have been synthesized: (a) [Ru(L)(bipy)Cl](PF6) where {bipy = bipyridine,...     

Assessment of Environmental Quantitative Variation of Diosgenin in Fenugreek Seeds via High-Performance Thin-Layer Chromatography Method

JPC – Journal of Planar Chromatography – Modern TLC - Fenugreek is one of the oldest medicinal plants known by mankind. The aim of this study is to evaluate the effect of environmental...     

Sub-ppt level voltammetric sensor for Hg2+ detection based on nafion stabilized l-cysteine-capped Au@Ag core-shell nanoparticles

Journal of Solid State Electrochemistry - Bimetallic nanoparticles (BMNPs) have received considerable attention due to their distinctive properties when compared to the corresponding monometallic...     

Studies of phononlike low-energy excitations of protein molecules by inelastic x-ray scattering

Molecular dynamics simulations and neutron scattering experiments have shown that many hydrated globular proteins exhibit a universal dynamic transition at TD = 220 K, below which the biological activity of a protein sharply diminishes. We studied the phononlike low-energy excitations of two structurally very different proteins, lysozyme and bovine serum albumin, using inelastic x-ray scattering above and below TD. We found that the excitation energies of the high-Q phonons show a marked softening above TD. This suggests that the large amplitude motions of wavelengths corresponding to this specific Q range are intimately correlated with the increase of biological activities of the proteins.     

Impact of Bi2O3 addition on the normal state properties of Bi3.4Pb0.3Sr2Ca1.3−x RExCu2Oy ceramics

The impact of Bi₂O₃ addition on the structural, microhardness (Vickers microhardness (VHN)), resistivity and Hall coefficient measurements of Bi_3.4Pb_0.3Sr₂Ca_1.3−x RE_xCu₂O_y ceramic samples with various x and RE is investigated. X-ray diffraction results indicate that all the peaks belong to Bi: 2212 and 2201 phases. The moderate amount of 2212 phase exists as a major phase, while the 2201 phase as a minor. The net intensity of all peaks I_max for 2212 phase increases with Y as compared to undoped sample, followed by a gradual decrease with further increase in rare earth (RE) up to La. While the vice versa is recorded for both 2201 phase and VHN. Except Y sample, a good link between flake-type grains is observed in the SEM photographs of the considered samples. The electrical resistivity turns from quiet metallic for undoped sample to semiconducting behavior for all substituted samples without any transition to the superconducting state. The Hall coefficient sign is found to be positive for undoped and Y samples and it changed from positive to negative for the other RE-substituted samples. The possible reasons for superconductivity quenching by RE substitution in this type of ceramic materials are reported.     

Experimental dipole moments for nonisolatable acetic acid structures in a nonpolar medium. A combined spectroscopic, dielectric, and DFT study for self-association in solution

Acetic acid can exist in many possible structural forms depending on its surrounding medium. A recently developed inverse problem methodology (J. Phys. Chem. B 2007, 111, 13064-13074) was utilized in order to elucidate acetic acid structures in a dilute nonpolar medium. In this regard, simultaneous and stopped-flow measurements of the bulk solution densities, refractive indices, relative permittivities, and IR spectra of acetic acid in toluene were performed at several different concentrations in a semibatch closed-loop experimental setup at 298.15 K and 0.1013 MPa. This combined IR spectroscopic and dielectric, density, and refractive index analysis was employed in order to distinguish acetic acid structures and to further determine the dipole moments of the monomer, cyclic dimer, and "lumped-sum" open dimers. The infrared spectra were first analyzed to provide qualitative understanding as well as quantitative estimates for each acetic acid species. Subsequently, the dipole moments of these species were calculated using a direct approach which was primarily based on response surface models. The present method allows the determination of individual dipole moments not only for the monomer but also for the cyclic dimer and the open dimer. The results obtained from this study experimentally show that the cyclic dimer with centrosymmetric structure has a dipole moment approximately 0 D. The results also suggest that the linear dimers are present as mixtures of linear dimers structures. The existence of the linear dimers mixture was also indicated by the experimental infrared analysis of the OH-stretching region (particularly for measurements in n-hexane as solvent) and comparison of these spectra with DFT predictions. Finally, the present methodology which incorporates simultaneous physicochemical and spectroscopic analysis is undoubtedly useful for physicochemical characterization for other nonisolatable solute species and self-associated structures in solution.     

Development of extraction procedures for the determination of imidacloprid: application to residue analysis and dynamics of two formulations in Chinese cabbage

This study was undertaken to investigate whether an additional column clean-up procedure can affect the accuracy of an analytical method developed for the determination of imidacloprid residues in Chinese cabbage. Thereafter, the residue levels and the degradation rates of imidacloprid were investigated in experimental Chinese cabbage plots after treatment with two different commercial formulations: emulsifiable concentrate (EC) and wettable powder (WP). The analyte was determined using high-performance liquid chromatography-ultraviolet detection (HPLC-UVD) and confirmed by high-performance liquid chromatography-mass spectrometry (HPLC-MS) in the select ion-monitoring mode. The mean recoveries ranged from 75.34 to 98.00% and 96.95 to 100.97%, with relative standard deviations of 0.86-4.14 and 1.22-3.52%, in samples treated with and without additional column clean-up procedures, respectively. The minimum detectable amount of imidacloprid was 4 ng, while the limits of detection and quantitation were 0.2 and 0.5 ppm, respectively. The degradation of pesticide was monitored throughout a period of 13 days under greenhouse conditions. Although the behaviors of the EC and WP formulations appear to be similar, the absolute residue levels obtained with EC and WP treatments differed slightly. When imidacloprid formulations were applied (as foliar treatments) according to the recommended rate, the final residues (13 days post-treatment) in Chinese cabbage were much lower than the maximum residue limit (MRL = 3.5 ppm) established by the Korean Food and Drug Administration. Taken together, our study suggests that the analysis of imidacloprid can be performed without an additional column clean-up procedure, and the decline curve and the residue levels in Chinese cabbage could change if the same active ingredient is used in different formulations.     

Heavy metal removal using SiO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> binary oxide: experimental design approach

Sorption of Ni²⁺ and Cd²⁺ as heavy metals ions at the interface of the binary oxide TiO₂-SiO₂ was investigated. In addition, physical properties of TiO₂-SiO₂ matrices such as BET surface area, X-ray diffraction, and point of zero charge (pH_PZC) were measured. Statistical design of experiments was applied to find the conditions of sorption at which the maximum heavy metal removal was achieved. A second order polynomial function was used to correlate the independent variables (pH, metal ion concentration, and shaking time) and response (heavy metal removal). Values of regression parameters were determined by the computer program, Design expert^® (Stat-Ease Inc.). The quality of fit of the polynomial model equation was expressed by the regression coefficient R ². The sorption results showed that the pH is the most significant factor. In turn, the sorbed percentage reached 100% at high initial concentration and long shaking times due to formation of hydroxyl compounds between the ions and TiO₂-SiO₂ matrices. The results show that there is a Gaussian (normal) distribution of residuals (squared differences between experimentally observed and predicted values from the model), and also that the differences between observed and predicted values are in the range of ±5%. These indicate that experiments were well-conducted and the results have no significant error.