Theories and models in symbiogenesis

Two modern theories of biological evolution, one by Carl Woese, and the other by Lynn Margulis, are modelled with Volterra–Hamilton systems. Their predictions are evaluated and compared within this modelling framework. For example, Woese's theory turns out to suffer from instability in its chemical exchanges processes, whereas Margulis’ does not. An introduction to the mathematical and biological ideas is included.     

Nonlinear prediction of crown–of–thorns outbreaks on the great barrier reef

The Zakai form of nonlinear prediction theory is used to estimate yearto-year state changes in crown-of-thorns starfish populations of the Great Barrier Reef. Taking the previously defined coral-state diffusion as observation process and the starfish-state diffusion as signal process, a least squares polynomial regression curve recently derived for simultaneously collected starfish/coral state data is used to set up the prediction preliminaries, Numerical results are not inconsistant with starfish outbreak values of the last 5 years and yield an expected high value for 1987. However, because of large error in the data it is doubtful that a more refined mesh for the Mihlstein approximations used to evaluate the Îto stochastic integrals involved in Zakai theory would improve the accuracy of predictions.     

Electroactive mesoporous tantalum oxide catalysts for nitrogen activation and ammonia synthesis

A new mesoporous Ta oxide catalyst for conversion of dinitrogen to ammonia shows strong evidence for a novel mechanism involving low valent Ta on the surface, supporting recent work in organometallic chemistry using low valent early transition metals for dinitrogen cleavage.     

Sulfated and phosphated mesoporous Nb oxide in the benzylation of anisole and toluene by benzyl alcohol

Materials possessing the high acidities of sulfated zirconia and the diffusion properties of mesoporous oxides are predicted to have numerous applications in the petrochemical industry. Because of surface deactivation and loss of structure under highly acidic conditions, there are few examples of materials which meet these specifications. In this work, mesoporous Nb oxide was treated with 1 M sulfuric acid or phosphoric acid and evaluated for their catalytic activities in the benzylation of toluene or anisole with benzyl alcohol. Characterization by XRD, nitrogen adsorption/desorption, and TEM demonstrated that the mesostructure was surprisingly stable to acid treatment. Pyridine adsorption and infrared spectroscopy (IR) showed a mixture of Lewis and Bronsted sites before and after acid treatment. Titration with a series of indicators demonstrated that sulfated mesoporous Nb oxide possesses a pKa of -8.2 and 31.784 mmol/g acid sites, roughly 100 times stronger than either bulk phosphated or sulfated niobia, which both possess pKa values in the range of -3.0. The best catalytic results in this study were achieved when using mesoporous Nb oxide treated with sulfuric acid; the conversion of benzyl alcohol with anisole to the benzylation product was 100% in 30 min, which is 200 times faster than the bulk catalyst. The extremely high activity was rationalized by the high number of strong Br?nsted sites on the surface coupled with the superior diffusion properties of the mesoporous system.     

Synthesis and characterization of a new family of electroactive alkali metal doped mesoporous Nb, Ta, and Ti oxides and evidence for an Anderson transition in reduced mesoporous titanium oxide

Recently we reported that mesoporous niobium oxide can be chemically reduced by Na-naphthalene while fully retaining its mesostructure. This was the first report of a molecular sieve acting as a stoichiometric electron acceptor. Herein we expand on the initial work by presenting a detailed study on Li-, Na-, K-, Rb-, and Cs-reduced samples of mesoporous Nb oxide, as well as Li-reduced mesoporous Ta and Ti oxides. While the Nb- and Ta-based materials fully retained their structure on reduction as determined by X-ray diffraction (XRD) and nitrogen adsorption, the Li-reduced Ti material retained high surface area and narrow pore size distribution, but lost its diffraction pattern, indicating an increased level of disorder in this material. X-ray photoelectron spectroscopy (XPS) and UV-visible reflectance spectroscopy revealed that all reduced mesoporous oxides studied have a similar electronic structure, corresponding to the presence of a disordered impurity band in the material lying between the valence band and the conduction band. Electron paramagnetic resonance (EPR) studies suggest that the electron in this impurity level is unpaired and best described as a free electron, only loosely bound to the alkali or transition metal. SQUID magnetometry showed that all reduced materials are paramagnetic, further confirming the presence of unpaired electrons in the structure. All materials in this study were insulating with the exception of the Li-reduced mesoporous Ti material, which was highly conducting, possibly due to an Anderson transition. Electrochemical studies on the unreduced mesoporous oxides demonstrated that while the Ta and Nb materials are capacitors with only a small degree of reversible electrochemical behavior in the bulk sample, the Ti material was an electrical conductor with fully reversible redox behavior.     

Proprietà di 20 ordine di un riferimento isotropo

We extend to the isotropic case, by adapted non-holonomic techniques [1], 2^° order properties of a relativistic frame of reference, generalized in the polar sense [2,3]: Riemann and gravitational tensors decomposition, Lie derivative of the Ricci rotation coefficients, commutation formulae and finally Bianchi identity. All the decomposition tensors are formally invariant (as regards the standard case), by means of the longitudinal derivative extension. Received: June 14, 2000?Published online: October 2, 2001     

Orotic acid: a milk constituent Enzymatic determination by means of a new microcalorimetric method

The presence of orotic acid (a precursor of nucleic acid) in milk is very important in order to ensure its nutritional value and good conservation. In the literature, chromatographic, spectrophotometric and polarographic methods are reviewed. The reported values have a very wide interval range (19-664 mg l(-1)) and a low precision. The new method proposed in this article employs an enzymatic reaction. It has been improved on standards and then tested on milk samples. The same samples were also tested by means of a known spectrophotometric method. The new analytical method for orotic acid determination is reliable; the results are more accurate and more precise if compared with the usual methods, and it shows the same sensibility. The calorimetric analysis is faster and easier, owing to the fact that no sample treatments are required.     

Electromagnetic corrections to neutrino processes in the leading logarithmic approximation,the value of sin θ and the W and Z masses

The parameters of the Weinberg-Salam model can be defined by amplitudes at a momentum scale M = O(M_W, M_Z). We derive the leading logarithmic e.m. correction to the relations giving the neutrino amplitudes at a momentum scale μ ? M in terms of sin²θ(M), α(M), M_W and M_Z. For leptonic processes, the Fermi constant is not corrected, but a running, universal, sin²θ(μ) > sin²θ(M) should be used. The Fermi constant for semileptonic processes is renormalized by a factor $\text{?(μ) > 1}$, for charged currents, and is not renormalized, for neutral current processes. The latter are described by the same sin²θ(μ) as the leptonic ones. We estimate that sin²θ(M) is about 0.013 smaller than the value of sin²θ obtained from semileptonic data with no correction, thereby improving the agreement with grand unified theories. The prediction for W (Z) masses and widths in terms of the low energy parameters are discussed. Using previous calculations at order α, we obtain predictions for the masses which are accurate up to and including terms of order (αlnM²)².