Synthesis,Characterization, and Electrochemical Properties of a Novel Macrocylic Ligand and its Transition Metal Complexes

Summary.  2,3-Dibromo-6,7,13,14,15,16,22,23-octahydro-14,15-bis-(hydroxyimino)-tribenzo [e,k,q][1,4,7,10,13,16]tetraoxadiazacyclohexadecine (LH₄) was prepared by condensation of 1,2-bis-(2′-aminophenoxyethoxy)-4,5-dibromobenzene with cyanogen-di-N-oxide. Mono-, di-, and trinuclear transition metal complexes of this ligand ((LH₃)₂Ni, (LH₃)₂Zn, (LH₃)₂Co, (LH₃)₂Cu, (LH₃)₂Fe, (LH₃)₂(UO₂)₂(OH)₂, (LH)₂Cu₃, (LH)₂Co₃) were synthesized under basic conditions. The electrochemical properties of the mono- and dinuclear complexes were studied by cyclic voltammetry in DMSO solution containing TBAP. The results showed that all redox processes are based on the metal center and the oxime ligands stabilize the Ni(III), Fe(III), Co(III), and Cu(III) species formed during oxidation. The Fe(II) and U(VI)O₂ complexes displayed a different behaviour: a reduction peak with the corresponding anodic signal during the reverse scan was observed. The oxime moiety also stabilizes U(V)O₂ which forms during the reduction process of the uranyl complex. Cu(II) was adsorbed on the electrode surface upon scanning cathodically. Received August 20, 2001. Accepted (revised) October 17, 2001     

Determination of heavy metal concentrations in plants exposed to different degrees of pollution using ICP-AES

Plant samples (Plantago lanceolata – narrow leaf plantain and Cichorium endiviae – endive) were collected in the surroundings of heavy metal emission sources and in other less contaminated areas. After digestion in a closed microwave system using HNO₃, the concentrations of Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn were determined using ICP-AES. Detection limits for all the elements of interest are given. Differences in heavy metal uptake rate between both plant species were observed. The uptake is more intensive for endive than for narrow leaf plantain. High concentrations of some heavy metals were determined in the unwashed plant samples as a result of exposure to aerosols. Tukeys statistical test was used to confirm the discrepancy of Cr concentration in plant samples from various areas. Washing the leaves with water was found to remove a large amount of water-soluble aerosols.     

New BF(-)(4) and ClO(-)(4)-selective membrane electrodes and their pharmaceutical applications

The construction and general performance characteristics of ion-selective membrane electrodes sensitive to BF(-)(4) and ClO(-)(4) anions, respectively, are described. All electrodes show near-Nernstian responses in the range 10(-2) -10(-5)M. The selectivity of the electrodes to a number of organic and inorganic anions are reported. The electrodes are useful in the potentiometric determination of a few pharmaceutical preparations. The method is simple, rapid and does not require prior sample pre-treatment.     

Ultrahigh 47-dB optical drop rejection multiwavelength add--drop filter using spatial filtering and dual bulk acousto-optic tunable filters

A new high-speed, ultrahigh cross-talk-suppression multiwavelength add-drop optical filter structure is demonstrated with two bulk acousto-optic tunable filters. With simple spatial blocks, an average -47-dB optical suppression is measured for the unwanted wavelengths at the filter output ports. The filter is tested for the three standard visible wavelengths, red, green, and blue, and demonstrates a switching time of 0.65micros and an average optical loss of 5 dB. Applications for this filter include multiwavelength switching applications such as wavelength-division-multiplexed optical communications.     

Learning networks in rainfall estimation

This paper utilizes Artificial Neural Networks (ANNs), standard Support Vector Regression (SVR), Least-Squares Support Vector Regression (LS-SVR), linear regression (LR) and a rain rate (RR) formula that meteorologists use, to estimate rainfall. A unique source of ground truth rainfall data is the Oklahoma Mesonet. With the advent of the WSR-88D network of radars data mining is feasible for this study. The reflectivity measurements from the radar are used as inputs for the techniques tested. LS-SVR generalizes better than ANNs, linear regression and a rain rate formula in rainfall estimation and for rainfall detection, SVR has a better performance than the other techniques.Mathematics Subject Classification: 30C40     

Stochastic simulation of thermally assisted magnetization reversal in sub-100 nm dots with perpendicular anisotropy

Thermally assisted magnetization reversal of sub-100 nm dots with perpendicular anisotropy has been investigated using a micromagnetic Langevin model. The performance of the two different reversal modes of (i) a reduced barrier writing scheme and (ii) a Curie point writing scheme are compared. For the reduced barrier writing scheme, the switching field H_swt decreases with an increase in writing temperature but is still larger than that of the Curie point writing scheme. For the Curie point writing scheme, the required threshold field H_th, evaluated from 50 simulation results, saturates at a value, which is not simply related to the energy barrier height. The value of H_th increases with a decrease in cooling time owing to the dynamic aspects of the magnetic ordering process. Dependence of H_th on material parameters and dot sizes has been systematically studied.     

Synthesis, characterization, and electrical and electrochemical properties of sandwich dilutetium tetraphthalocyanine

Lu2Pc2 and lithium hexylthio-phthalocyanine have been used to synthesize [Lu2(Pc)4] which exhibits variable range hopping conductivity as inorganic semiconductors and also observed electrochromic effect from cyclic voltammetric (CV) measurement.     

Superwide-angle coverage code-multiplexed optical scanner

A superwide-angle coverage code-multiplexed optical scanner is presented that has the potential to provide 4 pi-sr coverage. As a proof-of-concept experiment, an angular scan range of 288 degrees for six randomly distributed beams is demonstrated. The proposed scanner achieves its superwide coverage by exploiting a combination of phase-encoded transmission and reflection holography within an in-line hologram recording-retrieval geometry. The basic scanner unit consists of one phase-only digital mode spatial light modulator for code entry (i.e., beam scan control) and a holographic material from which we obtained what we believe is the first-of-a-kind extremely wide coverage, low component count, high speed (e.g., microsecond domain), and large aperture (e.g., > 1-cm diameter) scanner.     

Zur struktur des diethylgermanium-diphenylsiliciumoxids und zur konformation von achtringen mit silicium und germanium

Diethylgermanium-diphenylsilicon oxide [(Et₂Ge)O(Ph₂Si)O]₂ has been prepared by reaction of diethylgermanium dichloride and diphenyldihydroxysilane. Spectra and X-ray analysis showed the presence of a puckered eight-membered silicon—germanium—oxygen ring. The ethyl groups of the germanium atoms are disordered. A procedure is proposed for eight-membered rings with low symmetry to obtain a classification into clearly explaining ring forms based on exact or approximated planes put through as many ring atoms as possible. All of the 42 published eight-membered rings with silicon or germanium and oxygen, nitrogen or carbon could be classified by this method.