Modified PZT ceramics as a material that can be used in micromechatronics

Results on investigations of the PZT type ceramics with the following chemical composition: Pb_0.94Sr_0.06(Zr_0.50 Ti_0.50)_0.99 Cr_0.01O₃ (PSZTC) which belongs to a group of multicomponent ceramic materials obtained on basis of the PZT type solid solution, are presented in this work. Ceramics PSZTC was obtained by a free sintering method under the following conditions: T _sint = 1250 °C and t _sint = 2 h. Ceramic compacts of specimens for the sintering process were made from the ceramic mass consisting of a mixture of the synthesized PSZTC powder and 3% polyvinyl alcohol while wet. The PSZTC ceramic specimens were subjected to poling by two methods: low temperature and high temperature. On the basis of the examinations made it has been found that the ceramics obtained belongs to ferroelectric-hard materials and that is why it may be used to build resonators, filters and ultrasonic transducers.     

Effect of Basic Amino Acids on Nickel Ion Reduction at a Mercury Electrode

In a 0.02 M borax solution (pH 8.5), basic amino acids (arginine, lysine, and ornithine) react with Ni²⁺ to form a mono‐ligand complex that is reduced at a mercury electrode at about ?0.85 V vs. Ag|AgCl|KCl (3 M). At a long time scale (staircase voltammetry; scan rate<50 mV s^?1), the complex reduction is a catalytic (EC′) process, the rate‐determining step being the regeneration of the reducible species by the reaction of the amino acid with free Ni²⁺. At a short time scale (differential pulse voltammetry or higher scan rate staircase voltammetry), the reaction rate is controlled by the diffusion of the complex. Although the same kind of complexation occurs with either basic amino acids or glycine, the last one does not induce a similar process. The peculiar effect of basic amino acids is due to the side chain that causes the ligand molecule to adopt a favorable orientation at the electrode surface. The differential pulse voltammetry peak current is proportional to the total amino acid concentration over the concentration range from 2 to 100 μM. Hence a voltammetric method for arginine determination in nutritional supplements was developed and validated using HPLC as reference method.     

Rapid analysis of organic farming insecticides in soil and produce using ultra-performance liquid chromatography/tandem mass spectrometry

A new method for the analysis of three ecological insecticides, namely azadyrachtin, spinosad (sum of spinosyn A and spinosyn D) and rotenone, in produce and soil samples is presented. Investigated compounds are one of the most significant insecticides authorized for organic farming crop protection in many countries. Extraction of the pesticides from plant and soil matrices was performed by using a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. The method entailed a single extraction of the investigated compounds with acidified acetonitrile followed by a dispersive solid-phase extraction cleanup step prior to the final determination by reverse-phase ultra-performance liquid chromatography/tandem quadrupole mass spectrometry (UPLC-MS/MS). Validation studies were carried out on cabbage, tomato and soil samples. Recoveries of the spiked samples were in the range between 67% and 108%, depending on the matrix and the spiking level. Relative standard deviations for all matrix–compound combinations did not exceed 12%. The limits of quantification were ≤0.01 mg kg⁻¹ in all cases, except for azadirachtin. The developed method was applied to the analysis of real samples originating from organic farming production.     

Darwin and mass-velocity relativistic corrections in the non-Born-Oppenheimer calculations of pure vibrational states of H2

The Darwin and mass-velocity relativistic corrections have been calculated for all pure vibrational states of the H2 using the perturbation theory and very accurate variational wave functions obtained without assuming the Born-Oppenheimer (BO) approximation. Expansions in terms of explicitly correlated Gaussians with premultipliers in the form of even powers of the internuclear distance were used for the wave functions. With the inclusion of the two relativistic corrections to the non-BO energies the transition energies for the highest states agree more with the experimental results.     

PPh4]3[W(CN)7(O2)].4H2O as the representative of the [M(L)7(LL)] class for nine-coordinate complexes

The photoinduced dissociation of a W-CN bond in [W(CN)8]4- in an aqueous solution under ambient conditions, in conjunction with the uptake of molecular oxygen, affords the W(VI) mixed-ligand complex anion [W(CN)(7)(eta2-O2)]3-, conveniently isolable as its [PPh4+] salt. Although research into the chemistry of cyanomolybdates and cyanotungstates has been pursued with great interest and vigor over several decades, there is a paucity of structurally characterized cyano-peroxo complexes of Mo and W. The side-on coordination mode of the peroxo moiety in [W(CN)7(eta2-O2)]3- has been ascertained with X-ray crystal structure determination [d(O-O) = 1.41 A; peroxo bite angle: 41.0 degrees ] and corroborated with vibrational spectroscopy [nu(O-O) = 915 cm(-1)]. The complex ion exhibits trapezoidal tridecahedral geometry and represents the new class of nine-coordinate complexes with one bidentate and seven monodentate ligands. Cyclic voltammetry shows a reversible redox behavior of [W(CN)7(eta2-O2)]3- in CH3CN with its standard reduction potential equal to 1.130 V. Generally, interest in atmospheric oxygen derives from the versatility of this molecule as a ligand and oxidant and extends to the physicochemical features it imparts to transition metals such as copper and iron in biological oxygen carriers.     

Selfadjointness of Integral and Matrix Operators

Criteria for selfadjointness of integral operators, includingmatrix operators, based on our earlier domination results areestablished. The range of applicability is elucidated by carefullychosen examples, not covered by previously known criteria.     

57Fe Mössbauer spectroscopy and X-ray diffraction study of complex metamict minerals. Part II

The magnetic behaviour of the nanocrystalline Ni_0.5Cu_0.5Fe₂O₄, synthesized by the co-precipitation method has been studied. The X-ray diffraction patterns confirm the formation of cubic spinel structure. The dc magnetization measurements show that the samples are superparamagnetic above the blocking temperatures and the blocking temperature increases with particle size. The reduction in saturation magnetization in the case of nanoparticles as compared to their bulk counterpart has been explained on the basis that the magnetic moments in the surface layers of a nanoparticle are in a state of frozen disorder. The hump in ZFC curve progressively shift to a lower temperature with increasing field and broader curves at higher field, suggests the spin-glass nature of the system.     

Structure of 1,4-dihydro-1-ethyl-4-iminecinnoline-3-carboxylic acids, classical isosters of quinolone antibacterials: Crystal structures of hydrochlorides of 7-chloro and 7-methyl derivatives

Crystal structures of hydrochlorides of 7-chloro- and 7-methyl-4-iminecinnoline analogs of antibacterial quinolones have been determined by X-ray diffraction methods. The cell parameters for the 7-chloro (1) analog in the space group P2₁/c are a = 9.061(1), b = 19.062(1), c = 7.310(1)Å, = 104.92(1)°, Z = 4, and D _calc = 1.569 g/cm³ and for the 7-methyl (2) analog in the space group P are a = 7.277(5), b = 9.080(5), c = 10.058(5) Å, = 106.10(1), = 102.38(1), = 90.18(1)°, Z = 2, and D _calc = 1.429 g/cm³. Despite geometrical equivalency of methyl and chlorine and some resemblance of their packings, the crystal structures are not isostructural. Each compound forms a strong intramolecular hydrogen bond between protonated 4-imine (a donor) and 3-carboxylic (an acceptor) groups. Compounds with a similar bond, but with reversed functionality and orientation of the 3-carboxylic group, form common quinolones, being mostly 4-oxoquinoline-3-carboxylic acids. The difference should exclude chemical affinity of 4-imine analogs to the guanine base of a bacterial DNA in DNA-gyrase complex, as proposed by Shen et al. ² for 4-oxoquinoline-3-carboxylic acids showing antibacterial activity. Also the free acidic function of a carboxyl group may significantly lower permeability of 4-imine-3-carboxylic analogs of quinolones. Surprisingly, they have demonstrated antibacterial activity comparable with that of nalidixic acid.