Interaction of Cu-dipeptide complexes with Calf Thymus DNA and antiproliferative activity of [Cu(ala-phe)] in osteosarcoma-derived cells

In this work the study of Calf Thymus DNA interaction with several Cu(l-dipeptide) complexes was reported. The binding stoichiometry (Cu(mmol)/DNAmol base) was determined and in an attempt to clarify the binding mode, EPR and CD experiments were performed. All the studied complexes interacted with DNA, in a more selective way than [Cu(H₂O)₆]²⁺, being the [Cu(ala-phe)] the complex with the highest interaction. The EPR experiments suggested that the monomeric species formed in solution were coordinated through a nitrogen atom of the DNA bases (inner-sphere binding) and the CD studies showed structural changes upon the DNA–complex interaction. Besides, the ratio Cu(mmol)/DNAmol base obtained by the binding stoichiometry experiments was close to that found by EPR and CD determinations. The effect on cell proliferation determined by the crystal violet bioassay on UMR106 rat osteosarcoma-derived cells showed that the [Cu(ala-phe)] complex exerted an antiproliferative action against this tumor line.     

Three term recurrence for the evaluation of multivariate orthogonal polynomials

In this paper we obtain some explicit three term recurrence relations for the determination of multivariate orthogonal polynomials. These formulas allow us to obtain evaluation algorithms of finite series of these polynomials.     

Bounds for the chaotic region in the Lorenz model

In a previous paper, the authors made an extensive numerical study of the Lorenz model, changing all three parameters of the system. We conjectured that the region of parameters where the Lorenz model is chaotic is bounded for fixed r. In this paper, we give a theoretical proof of the conjecture by obtaining theoretical bounds for the chaotic region and by using Fenichel theory. The theoretical bounds are complemented with numerical studies performed using the Maximum Lyapunov Exponent and OFLI2 techniques, and a comparison of both sets of results is shown. Finally, we provide a complete three-dimensional model of the chaotic regime depending on the three parameters.     

Study of the conditions for the determination of metamitron by differential pulse polarography

Summary The electrochemical behaviour of the herbicide 4-amino-3-methyl-6-phenyl-1,2,4 triazine-5(4H)-on (Metamitron) is studied in aqueous medium using voltammetric techniques, with the ionic strength adjusted to 0.1 mol/l in sodium perchlorate and using a Britton-Robinson buffer. Two reduction waves on the mercury drop electrode appear, at –0.49 V the first and the second folded at –0.95 V and –1.05 V. The system is identified as irreversible and fundamentally controlled by diffusion. Using differential pulse polarography the detection limit reached was 0.02 mg · l^–1 for the first wave with an error of less than 2%. Thus a method is proposed for the determination of Metamitron in soil, with a detection limit of up to 0.02 g/g.

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Untersuchung der Bedingungen zur Metamitronbestimmung durch Differential-Puls-Polarographie

     

Search for the KL-->pi 0 pi 0 e+e- decay in the KTeV experiment

The recent discovery of a large CP violating asymmetry in KL-->pi+pi-e+e- mode has prompted us to seach for the associated KL-->pi 0 pi 0 e+e- decay mode in the KTeV-E799 experiment at Fermilab. In 2.7 x 10(11) K(L) decays, one candidate event has been observed with an expected background of 0.3 event, resulting in an upper limit for the KL-->pi 0 pi 0 e+e- branching ratio of 6.6 x 10(-9) at the 90% C.L.     

The Effect of Growth and Curvature on Pattern Formation

Based on first principles, we derive a general model to describe the spatio-temporal dynamics of two morphogens. The diffusive part of the model incorporates the dynamics, growth and curvature of one- and two-dimensional domains embedded in ³. Our generalized diffusion process includes spatio-temporal varying diffusion coefficients, advection, and dilution terms. We present specific examples by analyzing a third order activator--inhibitor mechanism for the kinetic part. We carry out illustrative numerical simulations on two-dimensional growing domains having different geometries. Comparisons with former results on fixed domains show the crucial role of growth and curvature of pattern selection. Evidence is given that both effects might be biologically relevant in explaining the selection of some observed patterns and in changing or enhancing their stability.Dedicated to Professor Shui-Nee Chow on the occasion of his 60th birthday.     

The Weighted Bootstrap Mean for Heavy-Tailed Distributions

We study the performance of the weighted bootstrap of the mean of i.i.d. random variables, X ₁, X ₂,..., in the domain of attraction of an -stable law, 1<<2. In agreement with the results, in the Efron's bootstrap setup, by Athreya,⁽⁴⁾ Arcones and Giné⁽²⁾ and Deheuvels et al.,⁽¹¹⁾ we prove that for a low resampling intensity the weighted bootstrap works in probability. Our proof resorts to the 0–1 law methodology introduced in Arenal and Matrán⁽³⁾. This alternative to the methodology initiated in Mason and Newton⁽²⁵⁾ presents the advantage that it does not use Hájek's Central Limit Theorem for linear rank statistics which actually only provides normal limit laws. We include as an appendix a sketched proof, based on the Komlos–Major–Tusnady construction, of the asymptotic behaviour of the Wasserstein distance between the empirical and the parent distribution of a sample, which is also a main tool in our development.     

Search for the rare decay K(L)-->pi(0)e(+)e(-)

The KTeV/E799 experiment at Fermilab has searched for the rare kaon decay K(L)-->pi(0)e(+)e(-). This mode is expected to have a significant CP violating component. The measurement of its branching ratio could support the standard model or could indicate the existence of new physics. This Letter reports new results from the 1999-2000 data set. One event is observed with an expected background at 0.99+/-0.35 events. We set a limit on the branching ratio of 3.5x10(-10) at the 90% confidence level. Combining with the previous result based on the data set taken in 1997 yields the final KTeV result: BR(K(L)-->pi(0)e(+)e(-))<2.8x10(-10) at 90% C.L.