Valency

About: Valency is a research topic. Over the lifetime, 1632 publications have been published within this topic receiving 26141 citations.

Formal Cu valency, effective carriers and high Tc superconductivity

Abstract: A systematic study has been carried out on thesame sample in order to determine the role of oxygen deficiency and carrier concentration on the superconducting properties of Y1Ba2Cu3O7−δ (Tc=93K). Specifically we have measured the Hall coefficient, electrical resitivity, acsusceptibility and x-ray diffraction on this sample after successive steps in which the oxygen deficiency was controlled and determined from thermogravimetry. From our Hall effect data, analysed in terms of effective single-band carriers(R=−1/ne), we find that the normal state carrier density decreases with oxygen depletion and that the number of free carriers extrapolate to almost zero forδ=0.5. We note that for 0<δ<0.5 the average formal Cu valency must be larger than +2 and thatδ=0.5 is exactly the degree of oxygen depletion at which the average Cu valency is equal to +2. In addition, it is interesting to point out that our Hall data combined with an appropriate resistivity for a dense material suggest a rather short mean-free path (<10A˚) On the other hand, the temperature dependence of resistivity as analysed by Gurwitch et al. (1), would imply that the mean-free path is substantially longer. We believe that this appearent contradiction is due to the estimation of the effective mass of the carriers in these structures.

How syntax restricts the lexicon: particle verbs and internal arguments

Abstract: Particles in German have the capacity to introduce new arguments when they combine with a verb. Based on this observation, I argue that the internal arguments of a particle verb are always introduced by the particle. I suggest that this follows from the fact that syntactically, the particle is the head of a maximal projection that occupies the single complement position of the verb; therefore, none of the base verb's arguments can be linked to a syntactic object position if a particle is present. In providing empirical evidence for my claim, I discuss in some detail the derivation of a variety of particle verbs, representing their semantics as Lexical Conceptual Structures, according to the framework developed in Jackendoff (1983, 1990)

Azionalità e transitività: Il caso dei preverbi latini

Abstract: The purpose of this paper is to demonstrate that the verbal prefixation modifies the actionality of Latin verbs: unprefixed atelic verbs (facio, molior, etc.) take telic valence when they are prefixed (conficio, emolior, etc.). We shall consider three types of opposition: 1) type molior «I prepare»: emolior «I accomplish». The unprefixed form represents an activity verb; the prefixed form is an accomplishment verb. Both verbs have two arguments. 2) type dormio «I sleep»: obdormio «I fall asleep». The unprefixed form is an activity verb; the prefixed form is an achievement verb. Both verbs have one argument. 3) type laboro «to strive for»: elaboro «to achieve (with effort)». The unprefixed form is an activity verb; the prefixed form is an accomplishment verb (or an achievement verb, depending on the degree of duration of the event the verb denotes). The former has one argument; the latter has two arguments. In the second type, the sole argument (=subject, in nominative case) of the unprefixed verbs is a direct internal argument; whereas, in the third type, the sole argument (=subject, in nominative case) of the unprefixed verbs is an external argument. The direct internal argument is the argument that measures out the event the verb denotes (=undergoer); the external argument is the argument that controls the event (=actor). It is shown that the acquisition of telic valence operates on the direct internal argument. Then, if a verb has a direct internal argument, that argument - whether it figures as direct object (type 1) or subject (type 2) - shifts, on the continuum of thematic relations, to the prototypical undergoer's pole. When the sole argument of a given verb is an external argument, the change of actionality of the verb needs an increase in valency: the verb in question takes a direct internal argument (=object, in accusative case). The unprefixed verbs corresponds largely, in the second type to inaccusative verbs, in the third type to inergative verbs. The

High temperature behaviour of the mixed valence compounds EuCu2Si2, YbCu2Si2 and the reference compounds CaCu2Si2 and GdCu2Si2

Abstract: Some physical properties (thermal expansions, magnetic susceptibilities and heat contents) of EuCu2Si2, YbCu2Si2 and reference compounds CaCu2Si2 and GdCu2Si2 have been measured in the temperature range 300–1000 K. The results obtained together with previous findings show that the valence of EuCu2Si2 is strongly dependent on T (valency, 2.9 at 100 K to 2.3 at 1000 K) while YbCu2Si2 maintains an almost constant valence value of 2.85, at least from 300 to 1000 K. For EuCu2Si2 an approximate determination of the energy required in the electronic process involved is also presented.