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The Ria Formosa is a shallow mesotidal lagoon on the south coast of Portugal, with natural biogeochemical cycles essentially regulated by tidal exchanges at the seawater boundaries and at the sediment interface. Existing data on nutrients in the water column and the sediment, together with chlorophyll a and oxygen saturation in the water column, are(More)
Information Keywords: Totally regular variables, Appell sequences, hypercomplex differen-tiable functions. Abstract The aim of our contribution is to call attention to the relationship between totally regular variables, introduced by R. Delanghe in 1970, and Appell sequences with respect to the hypercom-plex derivative. Under some natural nor-malization(More)
Information Keywords: Newton method; quaternions; radial derivative. Abstract In this paper we propose a version of Newton method for finding zeros of a quaternion function of a quaternion variable, based on the concept of quater-nion radial derivative. Several numerical examples involving elementary functions are presented.
Information Keywords: Hypercomplex Laguerre derivative, Appell sequences, exponential operators, functions of hypercomplex variables. Abstract In hypercomplex context, we have recently constructed Appell sequences with respect to a generalized Laguerre derivative operator. This construction is based on the use of a basic set of monogenic polynomials which(More)
This study (2002/2004) examines the effect of artificial reef (AR) structures off the southern coast of Portugal on biogeochemical process and nutrient cycling. Organic and inorganic carbon, nitrogen, phosphorus and chlorophyll a were determined monthly in sediment cores and settled particles for a two-year period. Ammonium, nitrates, phosphates, silicates,(More)
The physical and chemical changes in sediment and near bottom water caused by clam dredging were examined during July and September 1999, at two locations Vilamoura (VL) and Armona (AR), south coast of Portugal. Sediment cores and near bottom water were collected simultaneously before dredging (control samples) and within short time intervals (min-h) after(More)
In the recent past one of the main concern of research in the field of Hypercomplex Function Theory in Clifford Algebras was the development of a variety of new tools for a deeper understanding about its true elementary roots in the Function Theory of one Complex Variable. Therefore the study of the space of monogenic (Clifford holomorphic) functions by its(More)