Xenoestrogens: mechanisms of action and detection methods

Estrogenic compounds exert pleiotropic effects in wildlife and humans, and endogenous estrogens, like 17-estradiol, regulate growth and development of their target tissues. Environmental, industrial, or naturally occurring chemicals that possess estrogenic and/or antiestrogenic activities are termed xenoestrogens and may interfere with endocrine systems. These xenoestrogens are therefore defined as endocrine-active or endocrine-disrupting compounds. The estrogen receptor (ER) is the major regulatory unit within the estrogen-signaling pathway and the molecular mechanisms of estrogen and ER actions are described briefly. Based on the mechanism of ER action, in vitro test systems are described that can be employed for screening but also for the elucidation of mechanisms of action of (anti)estrogenic compounds. How screening assays and mechanistic studies can aid in human risk assessment for potential endocrine-active compounds is discussed also.     

掺杂Eu3+的Na24As2Mo22O83的合成及其发光特性

本文在固相合成掺杂稀土离子的单钨酸盐,混合碱土金属钨酸盐^[1-3]等体系的的系统研究基础上,采用固相反应法合成掺杂Eu^3 离子的Na24As2Mo22O83荧光体结晶粉末,并经元素分析,IR和X射线粉末衍射等分析手段确定了它的结构,探讨了Eu^3 离子在Na24As2Mo22O83中的发光和能量传递机理。     

Towards Minimal Addition Chains Using Ant Colony Optimisation

Modular exponentiation is one of the most important operations in almost all modern cryptosystems. It is performed using a series of modular multiplications. This operation is time consuming for large operands as is always the case in cryptography. Hence fast public-key cryptography software or hardware requires optimisation of the time consumed by a single modular multiplication and/or the reduction of the total number of modular multiplications required. This paper introduces a novel idea based on the principles of ant colony optimisation for finding a minimal addition chain that allows one to reduce the number of modular multiplications so that modular exponentiation can be implemented efficiently. The best addition chain reached by the ant system is compared to the one used in the m-ary and sliding window methods as well as with the best addition chain evolved by genetic algorithms. We demonstrate that the ant system significantly outperforms all these methods for any exponent size. ^★★ Research supported by FAPERJ () and CNPq ().     

A dynamic study of onion phases under shear flow: size changes

It has been shown that lyotropic lamellar phases under shear flow form structures corresponding to a close packed assembly of monodisperse multilamellar vesicles (onions). The size, which is fixed by the shear rate, can vary from a few microns to a tenth of a micron. In this study, we investigate for the first time the transient behaviour of size changes of onions under shear flow by means of small angle light scattering, direct microscopic observations, and conductivity measurements. We evidence two regimes: continuous and discontinuous. The nature of which (continuous or discontinuous) depends on the initial and final shear rate, and can be described by a dynamic phase diagram. Received: 14 November 1997 / Received in final form: 2 March 1998 / Accepted: 9 March 1998     

An extension of the Ccayley-Hamilton theorem to the case of supermatrices

Starting from the expression for the superdeterminant of (xI - M), whereM is an arbitrary supermatrix, we propose a definition for the corresponding characteristic polynomial and we prove that each supermatrix satisfies its characteristic equation. Depending upon the factorization properties of the basic polynomials whose ratio defines the superdeterminant, we are able to construct polynomials of lower degree which are also shown to be annihilated by the supermatrix.     

Some remarks on a paper by L. Carlitz

We study a family of orthogonal polynomials which generalizes a sequence of polynomials considered by L. Carlitz. We show that they are a special case of the Sheffer polynomials and point out some interesting connections with certain Sobolev orthogonal polynomials.     

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     

Pairing conjugate partitions by residue classes

We study integer partitions in which the parts fulfill the same congruence relations with the parts of their conjugates, called conjugate-congruent partitions. The results obtained include uniqueness criteria, weight lower-bounds and enumerating generating functions.     

On the properties of Newton-Euler pairs

If and are two sequences such that a₁=b₁ and , then we say that (a_n,b_n) is a Newton-Euler pair. In the paper, we establish many formulas for Newton-Euler pairs, and then make use of them to obtain new results concerning some special sequences such as and B_n, where p(n) is the number of partitions of n, σ(n) is the sum of divisors of n, and B_n is the nth Bernoulli number.     

A search for spontaneous emission of heavy clusters in the 127I nuclide

The results of an experimental search for spontaneous cluster decay in ¹²⁷I are presented. Several possible channels have been investigated considering an exposure of 33834 kg ^. day collected by a large-mass highly radiopure NaI(Tl) set-up deep underground in the Gran Sasso National Laboratory of the INFN. New lower limits on the lifetime of ²⁴₁₀Ne, ²⁸₁₂Mg, ³⁰₁₂Mg, ³²₁₄Si, ³⁴₁₄Si, ⁴⁸₂₀Ca, ⁴⁹₂₁Sc cluster radioactivity in ¹²⁷I have been achieved.