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- Elisabete Machado, Teresa M Coque, Rafael Cantó, A ˆ Ngela Novais, Joã, Carlos Sousa +2 others
- 2007

Objectives: To investigate the occurrence and the diversity of Ambler class A ESBLs among Enterobacteriaceae from different Portuguese clinical settings over a 2 year period (2002–04). Methods: One hundred and nine extended-spectrum b-lactamase (ESBL)-producing Enterobacteriaceae isolates from five geographically distant health institutions in Portugal were… (More)

An n × n real matrix A is said to be (totally negative) totally nonpositive if every minor is (negative) nonpositive. In this paper, we study the properties of a totally nonpositive matrix and characterize the case of a nonsingular totally nonpositive matrix A, with a 11 < 0 in terms of its LDU factorization (L(U)) is a unit lower-(upper-) triangular… (More)

The stabilization problem of positive linear discrete-time systems (PLDS) by linear state feedback is considered. A method based on a Brauer's theorem is proposed for solving the problem. It allows us to modify some eigenvalues of the system without changing the rest of them. The problem is studied for the single-input single-output (SISO) and for… (More)

The forest surface at the Valencian Community ascends to 1.247.090 hectares, which represents the 53.6 % of the total surface of the Valencian territory (2.327.194 hectares) and indicates that our community has a doubtless forest character. In fact, the hunting constitutes one of the forest activities of higher socioeconomic importance, setting in the third… (More)

- Rafael Cantó, Beatriz Ricarte, Ana M Urbano
- 2007

The positive realization problem is formulated as follows: Let H(z) ∈ R r×s (z) be a transfer matrix, it is said to admit a positive realization (A, B, C) if we find nonnegative matrices A ∈ R N ×N , B ∈ R N ×s , C ∈ R r×N and D ∈ R r×s such that H(z) = C[zI − A] −1 B + D. Moreover, this realization will be minimal if it has the minimal dimension. It has… (More)