Showing papers by "University of Udine published in 1984"

Scalarizing vector optimization problems

Abstract: A scalarization of vector optimization problems is proposed, where optimality is defined through convex cones. By varying the parameters of the scalar problem, it is possible to find all vector optima from the scalar ones. Moreover, it is shown that, under mild assumptions, the dependence is differentiable for smooth objective maps defined over reflexive Banach spaces. A sufficiency condition of optimality for a general mathematical programming problem is also given in the Appendix.

Oblique double layer potentials for the direct and inverse problems of electrocardiology

Abstract: A mathematical analysis of a model of the cardiac bioelectric sources generating the potential field in a bounded conducting volume is carried out. A boundary integral representation of the potential is given, which shows that, if the anisotropy of the cardiac muscle is taken into account, the bioelectric sources are characterized by an “oblique” double layer on the excitation wavefront. Boundedness conditions for the potential and jump relationships across the front are investigated. Uniqueness results for the inverse problem (i.e. the determination of the wavefront surface, given the potential on the volume boundary) are established.

Pumpellyite in low-grade metamorphic rocks from Ligurian and Lucanian Apennines, Maritime Alps and Calabria (Italy).

Abstract: In the Ligurian Apennines and the Brianzonese area of the Maritime Alps (Northern Italy), and in the Lucanian Apennines and Calabria (Southern Italy), pumpellyite formed during the Alpine metamorphism is widespread in terranes of Late Paleozoic to Miocene age, particularly in mafic ophiolites (Tethyan ophiolites of Jurassic-Early Cretaceous age). Pumpellyite developed under variable metamorphic conditions, which include zeolite, prehnite-pumpellyite, pumpellyite-actinolite, lawsonite-albite and blueschist facies. Pumpellyite from rocks belonging to all these facies was studied in 30 specimens of different chemistry, derived mostly from ophiolitic basalt and gabbro, but also from gneiss, amphibolite, and greywacke protoliths. Microprobe data give evidence of strong compositional variations of pumpellyite. The ranges are extreme for Al and Fetot (Al2O3=18.74–30.91; FeOtot=0.46–12.71), to a lesser extent for Mg (MgO=0.58–4.00), with a reciprocal variation of Al and Fetot which suggests that most Fe is Fe3+. Pumpellyite compositions can be related with the metamorphic conditions, particularly an increase of the Al/Fetot ratio with increasing pressure, but larger compositional variation for each facies in the Al-Fetot-Mg diagram than those previously described was recognized. Particularly the compositions of pumpellyite from the pumpellyite-actinolite and blueschist fades assemblages extend towards higher Fetot contents. Moreover, pumpellyites of the lawsonite-albite facies rocks result to be more aluminous than in blueschist facies; such relations appear to be inconsistent with that expected by the effects of pressure on the Al content. As the rocks are generally incompletely re-equilibrated, their bulk chemistry is not an important factor of pumpellyite composition; in fact the correlations of Al, Fetot and Mg are low. The local environment of crystallization, more evidently the composition of the precursor minerals, seems to be a major controlling factor. The observed topologic relations indicate that either the nature of the precursor mineral, or the presence of relict phases have a great influence on the pumpellyite composition. The observed variations within individual specimens, as well as the interspecimen ones, can be explained by small-scale inhomogeneities and in some cases by differences in the activity of O2. It can be therefore concluded that the composition of pumpellyite often reflects disequilibrium crystallization and cannot be generally used as an indicator of metamorphic conditions.

Features of volcanic tremors on Mt. Etna (Sicily) during the March August 1983 eruption

Abstract: The seismic analysis of the volcanic tremors preceding and accompanying the Etnean eruption of March–August, 1983 has shown a significant variation in the spectral content before the beginning of the eruption, the tremor peaks at 1.4 and 1.6 Hz — which might be associated with the feeding pipes of the NE crater (Schicket al., 1982a) — being the dominant feature of the spectra.

Characterization of a proton pump from pea stem microsomes

Abstract: The present work deals with the characterization of an ATP-dependent proton translocation monitored by the ΔpH probe acridine orange. The ATP-dependent proton translocation has an optimum activity at pH 6.5 and is substrate specific for ATP. It is stimulated by Cl−, HCO3− and Br−, but is insensitive to several monovalent cations. Divalent cations (Mg2+ or Mn2+) are required for proton translocation, while in the presence of Ca2+ no uptake is observed. NO3−, NO2− and citrate strongly inhibit proton uptake. On the contrary, F−, SO42−, malate, pyruvate, succinate, oxalate and acetate have no inhibitory effect. Proton uptake is stimulated by valinomycin and unaffected by molybdate. Two thiols, dithioerythritol and dithiothreitol, are able partially to prevent the FCCP-abolished proton uptake or partially restore the ATP-dependent proton translocation in FCCP-collapsed vesicles. It is suggested that pea stem microsomes possess an electrogenic ATPase, acting as a proton pump, which, on the basis of its characteristics, can be tentatively associated with membranes of tonoplast origin.

A formal basis for performance evaluation of natural language understanding systems

Abstract: The task of evaluating the performance of a natural language understanding system, despite its largely recognized relevance, is still poorly defined. It mostly relies on intuitive reasoning and lacks a sound theoretical foundation. This paper sets a formal and quantitative proposal for this task. In particular, a measure of performance that allows the basic input-output characteristics of a system to be evaluated is introduced first at an abstract level. The definition of concrete measures is then obtained by assigning actual values to the functional parameters of the abstract definition; some particular cases are shown and discussed in detail. Finally, the task of measuring performance in practice is considered, and a model for experimental performance evaluation is presented. Comparison with related works is also briefly discussed; open problems and promising directions for future research are outlined. A limited case study experimentation with the model proposed is presented in the appendix.

A geometric classification of inhomogeneities in continua with dislocations

Abstract: The paper proposes a geometric classification of inhomogeneities, in the sense of Noll, in bodies with continuous distribution of dislocations, based on the equivalence notion associated with homogeneous changes of the uniform reference.

Effects of 2-iodobenzanilide on potassium uptake, H+ extrusion and K+-stimulated ATPase of corn roots

Abstract: The carboxanilide systemic fungicide 2-iodobenzanilide (2-IB) after 2 h pretreatment at 0.25 mM inhibited K+ and SO42- uptake by excised corn roots (Zea mays L., cv. Dekalb 342) up to ca 70 and 40%, respectively. Proton extrusion from corn roots was also reduced by ca 50% after 1 h contact, and the microsomal K+-stimulated ATPase activity from corn roots and pea stems (Pisum sativum L., cv. Alaska) inhibited by 50 and 72%, respectively. In contrast, the Mg2+-ATPase activities of microsomes and mitochondria at pH 6.0 and 8.7, respectively, were unaffected. After 2 h of preincubation with 0.25 mM 2-IB, O2 consumption by corn roots and pea stems was inhibited by 12 and 18%, respectively. ATP content of corn roots was not altered by 2-IB treatment. Therefore, energy availability “in vivo” was unaffected and the primary effect on corn roots is suggested to be at the plasmalemma ATPase which forms the proton gradient. With isolated pea stem mitochondria, 0.25 mM 2-IB inhibited O2 consumption by ca 60% when NADH or malate plus pyruvate were added as substrates; when succinate was used O2 consumption was unaffected. The mode of action on isolated mitochondria was different from that shown for carboxin and also formerly attributed to the whole class of carboxanilide fungicides.

Lattice of Submodules and Isomorphism of Subquotients

Abstract: In this paper we consider the following problem: Let ℒ be a lattice and I(ℒ) = {[a,b]|a,B∈ℒ, A

Nonlinear filtering for markov processes: An L2 approach

Abstract: In this paper the Zakai equation of nonlinear filtering is directly derived as a mild stochastic differential equation on a Hilbert space. This is established when the state process is Markov, with a generator on some L2 space, and the observation process is corrupted by white noise. The main step is the derivation of a Feynman-Kac like formula for mild stochastic differential equations. In such a way well-known results in literature are generalized and at the same time their proofs are made much more simpler; moreover the Hilbert space setting is the most appropriate for approximation procedures. A final example is given in which the Zakai equation is written for a stochastic differential system in which the state equation is linear with an arbitrary number of noises, partly overcoming one of the up to now most serious limitations of such theory.

Oxidative addition of tetrabromo-1,2-benzoquinone totrans-carbonylchlorobis(triphenylphosphine)rhodium andtrans-carbonyliodiobis(triphenylphosphine)rhodium

Abstract: The oxidative addition of tetrabromo-1,2-benzoquinone to Rh(CO)X(PPh3)2 (X = Cl or I) has been studied. With the square planar complex Rh(CO)Cl(PPh3)2, two new isomeric hexacoordinated compounds; withcis andtrans PPh3 ligands, have been isolated and their structures are discussed on the basis of spectroscopic data. Thecis isomer in acetone solution quickly converts into thetrans. Such a conversion presumably proceeds through the dissociation of a triphenylphosphine molecule as seems indicated by the isolation of the pentacoordinated intermediate species Rh(CO)I(PPh3)(1,2-O2C6Br4), which has been identified by elemental analysis and spectroscopically characterized.

Boundary Value Problems

Abstract: In the previous chapters, we studied various kinds of questions concerning the initial value problem. We now propose to investigate other types of problems, in which the desired solution depends either on the values that it assumes at various points in its domain or on geometrical conditions (e.g., intersecting two given curves or being tangent to two lines), or on periodic conditions. Before studying such problems, we will discuss certain notions and results about continuous mappings on Euclidean spaces.

Well Posedness of Constitutive Equations of the Kinematical Hardening Type

Abstract: The purpose of the first part of these Lectures is to characterize the class of elastic-plastic materials starting from the more general class of the materials with elastic range and introducing a small number of ad hoc assumptions. This is done in the general framework of NOLL’s new theory of simple materials [6] After some preliminary work intended to re-define in this new context the class of materials with elastic range, a supplementary assumption on the nature of the inelastic behaviour defines a subclass of materials with elastic range of the rate type, which exhibits a number of mate rial properties considered as typical of elastic-plastic materials.

Dual relaxation and branch-and-bound techniques for multiobjective optimization

Abstract: This paper is concerned with duality results for multi objective (m.o.) optimization problems. The core of the paper is a duality theorem derived by usual separation techniques. This theorem generalizes known results in view of the applications to m.o. problems, which are presented in Section 3.

Existence and Uniqueness for the Cauchy Problem Under the Condition of Continuity

Abstract: In Chapter I, we studied the Cauchy problem (or initial value problem) for systems of normal type assuming strong regularity, i.e., the Lipschitz condition, for the functions on the right-hand side of the equation. In this chapter, we shall study the same problem but shall only assume that those functions are continuous. The biggest difference between the two cases will be that the uniqueness theorem no longer holds, as we see from the following classic example.

Existence and Uniqueness for the Initial Value Problem Under the Hypothesis of Lipschitz

Abstract: In this chapter, we shall study initial value problems in their various aspects: uniqueness, existence, domain of definition of the solutions and qualitative properties of the solutions. We shall assume that the functions that appear on the right side of the equations belong to a special class of continuous functions, the Lipschitz functions. This restriction allows us to treat the questions at hand with a remarkable ease.

Questions of Stability

Abstract: This chapter is devoted to presenting a panorama of the problems and methods of the theory of stability for ordinary differential equations. Roughly speaking, one could say that stability is the continuous dependence of the solutions as functions of the data on infinite intervals; the reason it is necessary to start a new chapter is that the theorems on continuous dependence in Chapter III are only valid on compact intervals. Keeping in mind that in general, physical phenomena develop over infinite intervals of time, the following observations may convince the reader of the necessity of undertaking a study of stability.