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Comparable changes in the volume of RETe3 materials caused by temperature and RE size have opposite trends to the incommensurate charge density wave modulation. This is unique behavior among all reported charge density wave materials.
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We examined the use of enterobacterial repetitive intergenic consensus (ERIC) sequences in PCR on the DNAs of various bacteria, bacteriophage, invertebrates, fungi, plants and vertebrates and have shown that complex ERIC-PCR patterns can be readily produced from all of these target organisms. A range of annealing temperatures was tested, from 52 degrees C (the commonly used annealing temperature) to 66 degrees C (the approximate Tm of ERIC primers). At the higher temperatures, most bands failed to amplify, the exception being a subset of bands from enterobacterial targets. It was concluded that ERIC-PCR does not necessarily direct amplification from genuine ERIC sequences.
Two adult, rumen-fistulated steers were fed, over four consecutive 3-week periods, Cu-deficient and normal hays with and without copper sulphate supplementation. Their rumen liquor levels of copper, zinc and manganese were determined correspondingly. The rumen liquor samples were split into 3 fractions by way of centrifugation, sodium dodecyl sulphate treatment of the sediment and filtration. The fractionation of the rumen liquor showed copper to be contained mainly in the water-soluble supernatant (68%), whilst zinc and manganese are more strongly linked to the microbial fraction (57 and 46%, resp.). The plant residue did not average but 9, 24 and 22% of copper, zinc and manganese, respectively. Copper sulphate supplementation to normal hay resulted in a significantly increased copper content in the supernatant and in the microbial fraction. At the same time, the zinc and manganese content values in the microbial fraction were found increased. However, the same copper sulphate supplementation to Cu-deficient hay was found to reduce highly significantly the copper level in the microbial fraction. It is supposed that the excessively high molybdenum content of this hay (2.5 ng/kg) has prevented any effect of the copper sulphate supplementation. The positive effects of copper sulphate supplementation on the zinc and manganese levels in the bacterial fraction were maintained even when feeding Cu-deficient hay rich in Mo.
The state of the art of analytical procedures based on solid-phase microextraction (SPME) and its applications to tin, mercury, arsenic, antimony, chromium, selenium, and lead determination in abiotic and biotic matrixes are critically reviewed from 1994 to present. First, sample pretreatment prior to SPME is evaluated, including a description of the most usual leaching procedures for sediment, soil, and biological samples. Because most organometallic species lack volatility, a derivatization step is mandatory prior to gas chromatographic (GC) determination, except for the volatile organometallics that can be directly extracted from the sample headspace or liquid phase by SPME. The most common derivatization procedures used in alkylation and hydridization reactions used for mercury, lead, and tin, as well as other procedures for the determination of total chromium and arsenic [i.e., trifluoroacetylacetonates for chromium (III) and thioglycol methylate for organic arsenic species] are reviewed. Critical variables usually evaluated along with the method development to improve the sensitivity of the extraction methods based on SPME, such as sampling size, stirring procedures, sampling temperature and pressure, polymer coating, and thermal desorption are reviewed. In addition, figures of merit of the different detection systems used in SPME combined with GC are evaluated. The validation of the reported analytical procedures with reference materials are also discussed in terms of precision and accuracy. Finally, future developments in the application of SPME to speciation are highlighted. Moreover, the capability of SPME automation for the derivatization-extraction procedures are also presented.
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Using a coupled BEM/FEM, this work describes a numerical method to compute the response and acoustic radiation for structures partially immersed in fluid. The structures and their responses are assumed to be symmetric about a symmetric plane. A symmetric complex matrix derived from the BEM and a reciprocal principle for surface acoustics is also used to represent the acoustic loading against the structures. In addition, selecting a proper Green's function based on image source method satisfies the boundary conditions of pressure release on the fluid surface and null normal velocity on the symmetric plane. Moreover, a boundary integral equation emerges when the field point approaches the structural surface where the normal derivative of the Green's function over partial, infinitesimal spheres is evaluated. These limiting values depend on locations of the field point on the surface. Owing to the symmetry of the acoustic loading matrix, the matrix for the coupled BEM/FEM is a banded, symmetric one, thereby allowing us to employ a variable banded storage method and invert of the matrix. Doing so markedly increases computational efficiency. Furthermore, an analytical solution of a spherical thin shell with the lower semi-sphere immersed in water is carried out by characteristic function expansions for shell equation and acoustic loading. These analytical solutions compare with the results obtained from the proposed numerical method. A good correlation for low frequencies is obtained and minor discrepancies are observed with an increasing frequency.