Switching off electron transfer reactions in confined media: reduction of [Co(dipic)2]- and [Co(edta)]- by hexacyanoferrate(II)

The kinetics of reduction of two cobalt(III) complexes with similar redox potentials by hexacyanoferrate(II) were investigated in water and in reverse micelle (RM) microemulsions. The RMs were composed of water, surfactant [(sodium(bis(2-ethylhexylsulfosuccinate)), NaAOT], and isooctane. Compared to the reaction in water, the reduction rates of (ethylenediaminetetraacetato)cobaltate(III) by hexacyanoferrate(II) were dramatically suppressed in RM microemulsions whereas a slight rate increase was observed for reduction of bis-(2,6-dipicolinato)cobaltate(III). For example, the ferrocyanide reduction of [Co(dipic)(2)](-) increased from 55 M(-1) s(-1)in aqueous media to 85 M(-1) s(-1) in a w(o) = 20 RM. The one-dimensional (1-D) and two-dimensional (2-D) (1)H NMR and FT-IR studies are consistent with the reduction rate constants of these two complexes being affected by their location within the RM. Since reduction of [Co(edta)](-) is switched off, in contrast to [Co(dipic)(2)](-), these observations are attributed to the penetration of the [Co(edta)](-) into the interfacial region of the RM whereas [Co(dipic)(2)](-) is in a region highly accessible to the water pool and thus hexacyanoferrate(II). These results demonstrated that compartmentalization completely turns off a redox reaction in a dynamic microemulsion system by either reactant separation or alteration of the redox potentials of the reactants.     

Optically detected magnetic resonance in the photoexcited triplet states of Ti(IV) and Zr(IV) cylopentadienyl complexes

The class of compounds (RCp)2MX2, where M is a group IV metal, Cp is cyclopentadienyl, R is an alkyl, and X is a halide, has been of continuing interest as precursors for olefin coordination polymerization catalysts. In this communication, we demonstrate that the technique of optically detected magnetic resonance (ODMR) reveals subtle differences in the composition of the frontier molecular orbitals associated with the nature of the alkyl substituents on the Cp rings.     

Spectroscopy of the deformed 126Ce nucleus

The even-even nucleus ¹²⁶Ce was studied via in-beam γ-ray spectroscopy using the ⁴⁰Ca + ⁹²Mo reaction at 190 MeV. Five bands were observed, one of them being identified for the first time. New connecting transitions were identified between the bands, which lead to new spin assignments. The bands are discussed in the framework of the IBM + broken pairs model. Received: 17 July 2002 / Accepted: 23 October 2002 / Published online: 18 February 2003 RID="a" ID="a"e-mail: costel.petrache@unicam.it Communicated by C. Signorini     

SU(6) model for odd-odd nuclei (OTQM/IBOM) and boson-aligned phase diagram inO(6) limit

We introduce the SU(6) model IBOM/OTQM for odd-odd nuclei and discuss the bands in O(6) limit. Bands are characterized by a particular type of phase correlations in the wave functions and exhibit splitting of the SU(3) analogs of Gallagher-Moszkowski bands.     

Excited states of 96Nb from the 96Zr(p,nγ)96Nb reaction

The γ-ray spectra of the ⁹⁶Zi(p, nγ)⁹⁶Nb reaction have been measured with Ge(Li) detectors at different bombarding proton energies between 1.3 and 5.1 MeV. γγ coincidences were observed at E_p = 4.7 and 5.0 MeV. On the basis of experimental results a level scheme of ⁹⁶Nb was deduced, and γ-threshold energies and γ-branching ratios were determined. Computed Hauser-Feshbach (p, n′) cross sections have been compared with experimental data obtained from the γ-ray measurements, and level spins and parities have been determined. The energies of ⁹⁶Nb levels were calculated on the basis of the parabolic rule, derived from the cluster-vibration model. The Racah multipole decomposition method was used also for the theoretical interpretation of several ⁹⁶Nb multiplet states.     

Self-aligning method of fiber-to-waveguide pigtailing

An innovative self-aligning technique for the pigtailing of optical fibers to buried channel planar waveguides is presented, based on selective etching. This technique utilizes a plug-and-socket mechanism that is intrinsically self-aligning and mechanically stable. The processes involved have been specifically designed to facilitate the bulk manufacture of pigtailed single or multiple fibers and waveguides. An optimized alignment geometry for the physical connection of fibers to waveguides is presented.     

Structure of low-lying levels in91Rb and93Rb

Life-times of low-lying levels in ₃₇ ⁹¹ Rb₅₄ and ₃₇ ⁹³ Rb₅₆ have been determined fromβ ^??γ coincidence measurements at the fission-product separator JOSEF. Values oft _1/2=17.0(8) ns and 2.0(2) ns have been obtained for the levels at 1,134 keV in⁹¹Rb and 267 keV in⁹³Rb, respectively, and upper limits could be deduced for several other states. Calculations in the frame of IBFM/PTQM have been performed for⁹¹Rb, the results of which allow an interpretation of the low-lying levels of this nucleus. For the 1,134 keV level the configuration [πg _9/2?2⁺] 7/2⁺ is suggested which lies close to or even below the 9/2 ₁ ⁺ level. The calculated half-life of 14 ns for the 1,134 keV level reproduces well the experimental value. The half-life of the 267 keV level in⁹³Rb favours the assignment ofI ^π=1/2^? to this state over the alternative 3/2^?.     

Silver staining of DNA in polyacrylamide gels

Nucleic acids can be detected at the picogram level using a quick and simple silver staining method (2). Using very thin polyesterbacked polyacrylamide gels, a further simplified protocol was compared to other widely used silver staining procedures. The improved protocol described here was the most sensitive, the fastest to perform, and had relatively few steps and reagents. This method also produced the least number of staining artifacts and offered images of high contrast.     

DNA amplification fingerprinting using arbitrary oligonucleotide primers

DNA amplification fingerprinting (DAF) is a strategy for genetic typing and mapping that uses one or more very short (≥5 nt) arbitrary oligonucleotides to direct the enzymatic amplification of discrete portions of a DNA template resulting in a spectrum of products characteristic of the DNA starting material. Polymorphisms from simple banding patterns are useful as genetic markers while more complex and informative patterns are suitable for DNA fingerprinting. The use of polyacrylamide gel electrophoresis and silver staining can adequately resolve the spectrum of DAF products into detailed and reproducible patterns.