Analysis of the toenail as a biomonitor of supranutritional intake of Zn,Cu, and Mg

The toenail was examined as a biological monitor of Mg, Zn, and Cu intake using an observational case control model. The One Source Cohort matched 63 individuals in Columbia Missouri who took the One Source multivitamin with 63 control individuals. The matching criteria were based on age, sex, ethnicity, smoking status, and body mass index. The multivitamin contained supra-nutritional levels of Se, Mg, Cu, and Zn. The toenail clippings were examined for these elements using instrumental neutron activation analysis (INAA). A statistical analysis did not indicate a significant difference for Mg, Cu, or Zn between the nails of One Source supplement users and control subjects (p<0.76, 0.55, and 0.85, respectively). The trace nutrient Se was used as an internal control. Previous studies have consistently demonstrated that toenail Se is positively correlated with Se supplement use and the analysis did result in a significant correlation in the toenails of One Source users and control subjects (p<1·10⁻⁴). This internal Se control suggests that the One Source Cohort is largely free from misclassification errors that could interfere with the biomonitor response for the supranutritional intake of Mg, Cu, and Zn.     

Nucleic acid secondary structures containing the double-headed nucleoside 5'(S)-C-(2-(thymin-1-yl)ethyl)thymidine

Oligodeoxynucleotides containing the double-headed nucleoside 5'(S)-C-(2-(thymin-1-yl)ethyl)thymidine were prepared by standard solid phase synthesis. The synthetic building block for incorporating the double-headed moiety was prepared from thymidine, which was stereoselectively converted to a protected 5'(S)-C-hydroxyethyl derivative and used to alkylate the additional thymine by a Mitsunobu reaction. The oligodeoxynucleotides were studied in different nucleic acid secondary structures: duplexes, bulged duplexes, three-way junctions and artificial DNA zipper motifs. The thermal stability of these complexes was studied, demonstrating an almost uniform thermal penalty of incorporating one double-headed nucleoside moiety into a duplex or a bulged duplex, comparable to the effects of the previously reported double-headed nucleoside 5'(S)-C-(thymin-1-yl)methylthymidine. The additional base showed only very small effects when incorporated into DNA or RNA three-way junctions. The various DNA zipper arrangements indicated that extending the linker from methylene to ethylene almost completely removed the selective minor groove base-base stacking interactions observed for the methylene linker in a (-3)-zipper, whereas interactions, although somewhat smaller, were observed for the ethylene linker in a (-4)-zipper motif.     

LYCOS: the Lyngby Co-Synthesis System

This paper describes the LYCOS system, an experimental co-synthesis environment. We present the motivation and philosophy of LYCOS and after an overview of the entire system, the individual parts are described. We use a single CPU, single ASIC target architecture and we describe the techniques we use to estimate metrics concerning hardware, software and communication in this architecture. Finally we present a novel partitioning technique called PACE, which has shown to produce excellent results, and we demonstrate how partitioning is used to do design space exploration.     

Decoupling of magnetically interacting crystallites of goethite

The magnetic properties of synthetic goethite, precipitated from a SiO₂-containing Fe(III) solution, have been studied. The Mössbauer spectra show the coexistence of a quadrupole doublet and a magnetically split component in a large temperature range. The area ratio of these two components depends strongly on temperature, indicating a normal superparamagnetic behaviour of isolated crystallites. This is in contrast to the behaviour normally exhibited by pure samples of microcrystalline goethite, in which strong magnetic interactions among the crystallites lead to a superferromagnetic behaviour. The results show that the magnetic interactions among the crystallites are drastically diminished when amorphous SiO₂ separates the goethite crystallites.     

Uniform spin wave modes in antiferromagnetic nanoparticles with uncompensated moments

In magnetic nanoparticles the uniform precession (q = 0 spin wave) mode gives the predominant contribution to the magnetic excitations. We have calculated the energy of the uniform mode in antiferromagnetic nanoparticles with uncompensated magnetic moments, using the coherent potential approximation. In the presence of uncompensated moments, an antiferromagnetic nanoparticle must be considered as a kind of a ferrimagnet. Two magnetic anisotropy terms are considered, a planar term confining the spins to the basal plane, and an axial term determining an easy axis in this plane. Excitation energies are calculated for various combinations of these two anisotropy terms, ranging from the simple uniaxial case to the planar case with a strong out-of-plane anisotropy. In the simple uniaxial case, the uncompensated moment has a large influence on the excitation energy, but in the planar case it is much less important. The calculations explain recent neutron scattering measurements on nanoparticles of antiferromagnetic α-Fe₂O₃ and NiO.     

Accurate depth-independent determination of acoustic backscatter coefficients with focused transducers

The accuracy of a method of data reduction for determining acoustic backscatter coefficients was tested using focused transducers and narrow-band pulses. Two phantoms with well-defined scattering properties were the bases of the tests, one having low attenuation and one with tissue-mimicking attenuation. The experimentally determined backscatter coefficients were found to be independent of transducer-to-scattering-volume distance and to agree very well with theoretical values, typically within 10%.