Development of quantitative vitellogenin-ELISAs for fish test species used in endocrine disruptor screening

The yolk protein precursor vitellogenin (Vtg) in plasma has proved to be a simple and sensitive biomarker for assessing exposure of fish to environmental estrogens. Within international bodies such as the Organization for Economic Cooperation and Development (OECD) work is ongoing to develop screening and testing programmes for endocrine disrupting effects of new chemicals, and in the focus of this development are the fish test species common carp (Cyprinus carpio), fathead minnow (Pimephales promelas), zebrafish (Danio rerio) and Japanese medaka (Oryzias latipes). In this study we have developed quantitative enzyme linked immunosorbent assays (ELISAs) for Vtg in common carp/fathead minnow, zebrafish and Japanese medaka. The assays were developed using a combination of monoclonal and polyclonal fish Vtg antibodies in a sandwich format, using stabilized Vtg from the test species as a standard. The carp Vtg ELISA has a working range of 1–63 ng/mL, a minimal detection limit of 0.6 ng/mL, and may also be used for quantification of Vtg in fathead minnow. In fathead minnow whole-body homogenate samples, the practical detection limit is 400 ng/mL due to the matrix effect. The zebrafish Vtg ELISA has a working range of 0.5–63 ng/mL, a minimal detection limit of 0.4 ng/mL, and a practical detection limit of 200 ng/mL in whole-body homogenate samples. The medaka Vtg ELISA has a working range of 0.25–16 ng/mL, a minimal detection limit of 0.1 ng/mL, and a practical detection limit of 125 ng/mL in whole-body homogenate samples. The intra- and inter-assay variations were below 20% for all assays. The assays were evaluated with sets of representative samples spanning the wide dynamic range of Vtg-levels found in fish exposed to environmental estrogens, and all three assays are currently undergoing international inter-laboratory validation.     

On the determination of crystallinity and cellulose content in plant fibres

A comparative study of cellulose crystallinity based on the sample crystallinity and the cellulose content in plant fibres was performed for samples of different origin. Strong acid hydrolysis was found superior to agricultural fibre analysis and comprehensive plant fibre analysis for a consistent determination of the cellulose content. Crystallinity determinations were based on X-ray powder diffraction methods using side-loaded samples in reflection (Bragg-Brentano) mode. Rietveld refinements based on the recently published crystal structure of cellulose Iβ followed by integration of the crystalline and amorphous (background) parts were performed. This was shown to be straightforward to use and in many ways advantageous to traditional crystallinity determinations using the Segal or the Ruland–Vonk methods. The determined cellulose crystallinities were 90–100 g/100 g cellulose in plant-based fibres and 60–70 g/100 g cellulose in wood based fibres. These findings are significant in relation to strong fibre composites and bio-ethanol production.     

Single crystal Raman study of potassium oxalate monohydrate,K2C2O4. H2O,and potassium oxalate monodeuterate,K2C2O4. D2O

Raman spectra of poly crystalline and single crystal K₂C₂O₄. H₂O and K₂C₂O₄. D₂O have been recorded at room temperature. From an earlier neutron diffraction study it is known that the space group is C⁶₂h. The water molecule occupies a C₂ site and the oxalate ion a C₁ site. The assigned water vibrations show small factor group splitting between g modes (Raman active) and u modes (IR active). The internal oxalate vibrations are found to have wavenumbers in good agreement with those reported from Raman studies of other oxalates.     

Investigations of reactions involved in flameless atomic absorption procedures : Part IV. A theoretical study of factors influencing the determination of aluminium

High-temperature equilibrium calculations are used to study potential interferences in the determination of aluminium by flameless a.a.s. The conditions for the formation of interfering aluminium compounds like AlO(g), Al₂O(g), Al₂O₃(s), AlOH(g), AlH(g), AlHO₂(g), AlS(g), AlN(g), AlN(s) and AlCl(g) have been calculated. The influence of kinetic parameters on the equilibrium calculations for the reactions involving carbon—oxygen and carbon—sulphur has been established by varying the input amount of carbon. The results indicate that even in the nanomole range the presence of elements like H, O, N, Cl and S may cause severe interferences during the atomization step (2300–2900 K)     

Compensation effect in the hydrogenation/dehydrogenation kinetics of metal hydrides

The possible existence of a compensation effect, i.e. concurrent changes in activation energy and prefactor, is investigated for the hydrogenation and dehydrogenation kinetics of metal hydrides, by analyzing a series of reported kinetic studies on Mg and LaNi(5) based hydrides. For these systems, we find a clear linear relation between apparent prefactors and apparent activation energies, as obtained from an Arrhenius analysis, indicating the existence of a compensation effect. Large changes in apparent activation energies in the case of Mg based hydrides are rationalized in terms of a dependency of observed apparent activation energy on the degree of surface oxidation, i.e., a physical effect. On the other hand, we find the large concurrent changes in apparent prefactors to be a direct result of the Arrhenius analysis. Thus, we find the observed compensation effect to be an artifact of the data analysis rather than a physical phenomenon. In the case of LaNi(5) based hydrides, observed scatter in reported apparent activation energies is less pronounced supporting the general experience that LaNi(5) is less sensitive toward surface contamination.     

Harmonic analysis of fractal measures

We consider affine systems inR ⁿ constructed from a given integral invertible and expansive matrixR, and a finite setB of translates,σ _bx:=R^–1x+b; the corresponding measure μ onR ⁿ is a probability measure fixed by the self-similarity $\mu = \left| B \right|^{ - 1} \sum\nolimits_{b \in B} {\mu o\sigma _b^{ - 1} } $ . There are twoa priori candidates for an associated orthogonal harmonic analysis: (i) the existence of some subset Λ inR ⁿ such that the exponentials {e^iλ·x}Λ form anorthogonal basis forL ²(μ); and (ii) the existence of a certaindual pair of representations of theC ^*-algebraO _N wheren is the cardinality of the setB. (For eachN, theC ^*-algebraO _N is known to be simple; it is also called the Cuntz algebra.) We show that, in the “typical” fractal case, the naive version (i) must be rejected; typically the orthogonal exponentials inL ²(μ) fail to span a dense subspace. Instead we show that theC ^*-algebraic version of an orthogonal harmonic analysis, namely (ii), is a natural substitute. It turns out that this version is still based on exponentialse ^iλ·x, but in a more indirect way. (See details in Section 5 below.) Our main result concerns the intrinsic geometric features of affine systems, based onR andB, such that μ has theC ^*-algebra property (ii). Specifically, we show that μ has an orthogonal harmonic analysis (in the sense (ii)) if the system (R, B) satisfies some specific symmetry conditions (which are geometric in nature). Our conditions for (ii) are stated in terms of two pieces of data: (a) aunitary generalized Hadamard matrix, and (b) a certainsystem of lattices which must exist and, at the same time, be compatible with the Hadamard matrix. A partial converse to this result is also given. Several examples are calculated, and a new maximality condition for exponentials is identified.     

Stability of rarefaction waves in viscous media

We study the time-asymptotic behavior of weak rarefaction waves of systems of conservation laws describing one-dimensional viscous media, with strictly hyperbolic flux functions. Our main result is to show that solutions of perturbed rarefaction data converge to an approximate, Burgers rarefaction wave, for initial perturbations w ₀ with small mass and localized as w ₀(x)= The proof proceeds by iteration of a pointwise ansatz for the error, using integral representations of its various components, based on Green's functions. We estimate the Green's functions by careful use of the Hopf-Cole transformation, combined with a refined parametrix method. As a consequence of our method, we also obtain rates of decay and detailed pointwise estimates for the error.This pointwise method has been used successfully in studying stability of shock and constant-state solutions. New features in the rarefaction case are time-varying coefficients in the linearized equations and error waves of unbounded mass (log (t)). These diffusion waves have amplitude (t ^-1/2logt) in linear degenerate transversal fields and (t ^-1/2logt) in genuinely nonlinear transversal fields, a distinction which is critical in the stability proof.     

Determination of stability constants of chelate complexes: Part II. Applications

The proposed simplified method for calculating the stability constants of chelate complexes from pH and pM measurements (Part I) is applied to two systems. On the basis of data reported by Österberg, the stability constants of copper o-phosphorylserylglutamic acid are calculated and good agreement is achieved. In addition, the stability constants of the mononuclear, binuclear and trinuclear silver complexes of TTHA (triethylenetetraminehexaacetic acid) were calculated from potentiometric pAg data. These calculations yielded the following values of the cumulative constants: log β_AgL=8.7, log β_AgHL= 17.6, log β_AgH2L= 23.8, log β_Ag2L= 14.0, log β_Ag2HL = 20.5, log β_Ag2H2L = 25.6, log β_Ag2L =17.0.