X-Band Pulsed ENDOR Study ofFe-Substituted Sodalite— The Effect of the Zero-Field Splitting

X-band (∼9.3 GHz) pulsed ENDOR measurements were carried out on⁵⁷Fe-substituted sodalite (FeSOD) which contains only one type of Fe(III) (S=) located at a framework site. The ENDOR spectrum recorded atg= 2 shows three doublets corresponding to the sixM_Smanifolds. The assignment of these signals was confirmed by hyperfine-selective and triple ENDOR experiments. The components of each of the doublets had different intensities, reflecting the different populations of the EPR energy levels at the measurement temperature, 1.8 K. ENDOR spectra were recorded at magnetic fields within the EPR powder pattern, and the field dependence observed showed an anisotropic behavior, unexpected from the isotropic character of the⁵⁷Fe(III) hyperfine coupling. This dependence was attributed to the high-order effects of the zero-field splitting (ZFS) interaction on the ENDOR frequencies. Three different theoretical approaches were used to account for the dependence of the ENDOR spectrum on the ZFS interaction. The first involves the exact diagonalization of the total spin Hamiltonian, the second uses third-order perturbation approximations, and the third employs an effective nuclear Hamiltonian for each of theM_Smanifolds. The simulations showed that the ENDOR signals of theM_S= ±5/2 (ν_±5/2) manifold are the least sensitive to the magnitude of the ZFS parameterDand are therefore the most appropriate for the determination ofa_iso. It is shown that at X band anda_isovalues of about 30 MHz, the perturbation approach is valid up toDvalues of 500 MHz if all three doublets are concerned. However, if only the ν_±5/2doublet is considered, then this approach is valid forD< 1000 MHz. The third approach was found inappropriate fora_isovalues of ∼30 MHz. Using the method of exact diagonalization together with orientation selectivity, the trends observed in the experimental spectra could be reproduced. The ENDOR spectra of the⁵⁷Fe-substituted zeolites ZSM5, L, and mazzite showed broad and ill-defined peaks since the ZFS of Fe(III) in these zeolites is significantly larger than that of FeSOD. Because this broadening is a high-order effect, it can be significantly reduced at higher spectrometer frequencies.     

Self-focusing in new kerr media: Large thermal nonlinearity in metallotetraphenylporphins

A large optical nonlinearity of thermal origin has been observed in acetone solutions of a series of tetraphenylporphin, TPPH₂, MnTPP(CH₃CO₂ ^–), FeTTPCI^-, CoTPP, NiTPP, and CuTPP. The nonlinear Kerr coefficient is sensitively dependent on the nature of central metals in the compounds. The Mn compound exhibits the largest coefficient, 6 × 10^–5 esu, for 514 nm laser wavelength. The use of prophins offers increased flexibility in the preparation of different Kerr media.Presented at the International Workshop on Squeezed and Correlated States in Quantum Optics, Moscow, December 3–7, 1990.     

Detection and quantitation of a bioactive compound in Vicia narbonensis L. seeds by capillary electrophoresis-mass spectrometry: a comparative study with UV detection

Capillary zone electrophoresis with mass spectrometry (CE-MS) and UV detection (CE-UV) was applied to the quantitative determination of gamma-glutamyl-S-ethenyl-cysteine (GEC), a bioactive and unstable compound present in Vicia narbonensis L. seeds. This compound is responsible for, among other negative effects, palatability reduction and grain toxicity. In order to carry out the quantitative analysis of GEC, different conditions (such as composition, concentration and pH of the background electrolyte, and type and time of extraction) were studied. Also, adequate conditions for electrospray-mass spectrometry of this bioactive compound were investigated. The best extraction conditions of GEC from V. narbonensis L. seeds flour were obtained using ethanol-water (70:30 v/v) for 45 min. The use of a 20 m ammonium hydrogen carbonate at pH 7 provided adequate analytical conditions compatible with the unstable nature of GEC as well as with the requirements of CE-UV and CE-MS analysis. A comparative study was carried out between the different figures of merit of CE-UV and CE-MS for quantitative purposes. Both techniques provided similar limit of detection and can be applied with confidence within the same linear dynamic range. However, reproducibility and speed of analysis were better using CE-UV. The developed methods were readily applied to quantify GEC in seeds of 21 genotypes of V. narbonensis L. A good agreement between CE-MS and CE-UV results was observed corroborating the usefulness of both approaches for quantitative purposes.     

Influence of the metal size in the structure of the complexes derived from a pentadentate [N(3)O(2)] hydrazone

The influence of the metal size in the nuclearity of the complexes derived from the hydrazone ligand 2,6-bis(1-salicyloylhydrazonoethyl)pyridine [H(4)daps] has been investigated. We have synthesised a series of new complexes [M(H(x)daps)] x yH(2)O, (x = 2,3; y = 0-3) with M = Ag (1), Cd (2), Al (3), Sn (4) and Pb (6), using an electrochemical procedure. The crystal and molecular structures have been determined for the mononuclear complexes [Sn(H(2)daps)(H(2)O)(2)] x 4H(2)O (5) and [Pb(H(2)daps)(CN)][Et(4)N] (7). Complex is the first neutral Sn(II) complex derived from a pentadentate hydrazone Schiff base ligand. Complex shows the lead coordinated to the hydrazone donor set and a cyanide ligand, being the first reported complex with the lead atom coordinated to a monodentate cyanide group. Additionally, we have synthesised the lead complex using chemical conditions, in the presence of sodium cyanide which allowed us to isolate the neutral complex [Pb(H(2)daps)] (8). Evaporation of these mother liquors led the novel compound [Pb(Hdaphs)(CH(3)COO)] (9). Complex 9 shows the initial ligand hydrolysed in one of the imine bonds giving rise to a new tetradentate ligand [H(2)daphs] coordinated to the lead atom and a bidentate acetate group. Moreover, the solution behaviour of the complexes has been investigated by (1)H, (113)Cd, (117)Sn and (207)Pb NMR techniques. In particular multinuclear NMR has provided new useful data to correlate factors such as oxidation state, coordination number and nature of the kernel donor atoms due to the new coordination found in complexes 5 and 7. The comparative study of the structures of the complexes derived from this pentadentate [N(3)O(2)] hydrazone ligand let us to conclude that the metal size is a key factor to control the nuclearity of the complexes derived from the ligand [H(4)daps].     

Multielement analysis in serum of healthy population of the metropolitan region of Rio de Janeiro in Brazil by SRTXRF

The determination of multielemental concentrations in physiological fluids is of considerable interest in clinical chemistry. Since it has been established these levels in human serum can be utilized as indicators for several pathological conditions. The multielement composition determination in human serum is important for the investigation of their role in human physiology and metabolism. From this research, more detailed studies on the health of individuals living in the metropolitan region of the state of Rio de Janeiro can be realized in order to improve the quality of life of these individuals. We studied 180 healthy volunteers (80 males and 100 females) aged 19 to 60 years. All the serum samples had been collected of people who live in the urban area of Rio de Janeiro City/Brazil. The measurements were performed at the X‐Ray Fluorescence Beamline at the Brazilian National Synchrotron Light Laboratory (LNLS), in Campinas, São Paulo. We were able to determine the concentrations of the following 11 elements: Na, P, S, Cl, K, Ca, Fe, Cu, Zn, Br and Rb. In this study, we used statistical analysis for the principal components. We were able to verify the presence of two factors that divided the elements into two groups: group 1 formed by elements: Cl, K, S and Ca and group 2 by elements Cu and Zn. Copyright © 2015 John Wiley & Sons, Ltd.     

Equivariant strong shape

In this paper we propose a construction of the equivariant strong shape for compact metrizable G-spaces using an equivariant version of so-called cotelescopes and the concept of a fibrant G-space.     

N,N′‐Bis(2‐tosylaminobenzylidene)benzene‐1,2‐di­amine

The conformation of the title compound, C₃₄H₃₀N₄O₄S₂, is strongly influenced by intramolecular N—H?N hydrogen‐bond interactions and by the rigidity endowed by the presence of a phenyl group between the imine N atoms. The molecule is not planar, with very short distances between the imine N atoms [N?N 2.753 (3) Å] and the amine N atoms [N?N 5.148 (4) Å]. Consequently, important changes in its conformation will be required if it is to act as a tetradentate ligand via its four N atoms.     

Bessel beam spatially truncated

We present a study of spiral structures generated by superposition of a truncated Bessel beam and a plane wave. One of the main characteristics of spiral structures is that the shape of spiral beams remains unchanged upon propagation. The results of experimental observations using a Mach-Zehnder interferometer are compared with the numerically calculated intensity distribution. We show that when spiral beams are disturbed by a nontransparent obstacle, the amplitude of the transmitted field is distorted at nearby distances behind that obstacle, but during free-propagation, it regenerates to its initial form.     

Locally Tabular $$\ne $$ Locally Finite

We show that for an arbitrary logic being locally tabular is a strictly weaker property than being locally finite. We describe our hunt for a logic that allows us to separate the two properties, revealing weaker and weaker conditions under which they must coincide, and showing how they are intertwined. We single out several classes of logics where the two notions coincide, including logics that are determined by a finite set of finite matrices, selfextensional logics, algebraizable and equivalential logics. Furthermore, we identify a closure property on models of a logic that, in the presence of local tabularity, is equivalent to local finiteness.