Showing papers on "Valency published in 2002"

Mn 3s exchange splitting in mixed-valence manganites.

Abstract: We present Mn $3s$ x-ray photoelectron spectra of manganese oxides with the Mn formal valency from $2+$ to $4+.$ We found that the ${\mathrm{Sr}}^{2+}$ doping or cation deficiency in manganites do not change the Mn $3s$ splitting in manganites with the Mn formal valency from $3.0+$ to $3.3+.$ We suggest that doping holes are localized in O $2p$ states.

Valency of rare earths in R In-3 and R Sn-3: ab initio analysis of electric-field gradients

Abstract: In $R{\mathrm{In}}_{3}$ and $R{\mathrm{Sn}}_{3}$ the rare earth (R) is trivalent, except for Eu and Yb, which are divalent. This was experimentally determined in 1977 by perturbed angular correlation measurements of the electric-field gradient on a ${}^{111}\mathrm{Cd}$ impurity. At that time, the data were interpreted using a point charge model, which is now known to be unphysical and unreliable. This makes the valency determination potentially questionable. We revisit these data, and analyze them using ab initio calculations of the electric-field gradient. From these calculations, the physical mechanism that is responsible for the influence of the valency on the electric-field gradient is derived. A generally applicable scheme to interpret electric-field gradients is used, which in a transparent way correlates the size of the field gradient with chemical properties of the system.

Electronic structure of the alpha and beta isomers of [Mo(8)O(26)](4-).

Abstract: The structure and bonding in alpha and beta octamolybdate anions have been investigated using density functional methods. In general, good computational-experimental agreement for the geometrical parameters has been obtained. The electronic structure of the anions has been probed with molecular orbital and Mulliken-Mayer methods. All Mo-O interactions have been found to be predominantly d(Mo)-p(O) in character. Several multicentered molecular orbitals can be described as sigma or pi closed-loop structures, but the proposed connection with the stability of the polyanions is not completely supported by the calculations. Mayer indexes correspond to fractional multiple character for terminal bonds and approximately single or low-order character for bridging bonds, in accordance with structural and bond valence results. The valency analysis has yielded similar overall bonding capacity for the various oxygen atoms. A distribution of the negative charge over all types of oxygen sites and metal charges considerably smaller than the formal oxidation states have been obtained from the Mulliken analysis.

A XANES Study of Cu Valency in Cu‐Doped Epitaxial ZnO

Abstract: Near-edge X-ray absorption (XANES) at the Cu K-edge was employed to study the valency of Cu (a potential p-dopant) in Cu-doped ZnO grown by molecular beam epitaxy. For a similar chemical environment, a shift in the onset of absorption can be interpreted as being due to a change in effective valency. We have studied this shift for both as-grown and argon ambient annealed (1000°C, 30 min) Cu-doped ZnO samples. The valency shift was measured against ab-initio standards calculated using feff8 as well as the standard samples Cu 2 O (+1 valence) and CuO (+2 valence). It was found for the flux region explored here that as-incorporated Cu assumes an effective valence of approximately +1 which increases towards +2 upon a 1000 °C argon ambient anneal. X-ray diffraction also shows the presence of both metallic Cu and Cu 2 O depending upon growth and annealing conditions.

Doped holes in edge-shared CuO2 chains and the dynamic spectral weight transfer in X-ray absorption spectroscopy

Abstract: We present a joint experimental and theoretical study of the electronic structure of the chain compounds A1 − xCuO2 (A=Ca,Sr,Ba) using O-K and Cu-L3 X-ray absorption spectroscopy. The doping-dependent behaviour in these systems differs from that of conventional 2D Cu-O networks formed by corner-shared CuO4 plaquettes. It follows from the strongly weakened inter-plaquette hybridisation due to the nearly 90deg Cu-O-Cu bond in the chains. Spectroscopically, this results in a) the different final states in the Cu-L3 spectra which can be used directly to "read-off" the Cu valency and b) a drastic reduction in the dynamic spectral weight transfer from the upper Hubbard band to the low-energy scale in the O-K spectra.

Extending the coverage of a valency dictionary

Abstract: Information on subcategorization and selectional restrictions is very important for natural language processing in tasks such as monolingual parsing, accurate rule-based machine translation and automatic summarization. However, adding this detailed information to a valency dictionary is both time consuming and costly.In this paper we present a method of assigning valency information and selectional restrictions to entries in a bilingual dictionary, based on information in an existing valency dictionary. The method is based on two assumptions: words with similar meaning have similar subcategorization frames and selectional restrictions; and words with the same translations have similar meanings. Based on these assumptions, new valency entries are constructed for words in a plain bilingual dictionary, using entries with similar source-language meaning and the same target-language translations. We evaluate the effects of various measures of similarity.

Effect of defects on ytterbium ion valency in YbB12

Abstract: An EPR signal from ytterbium ions with an integer valence of +3 was detected in the YbB12 intermediate-valence compound. The measurements were carried out on an YbB12 single crystal in the 1.6-to 4.2-K temperature interval. The EPR spectrum is interpreted as being due to the existence of exchange-coupled ytterbium ion pairs.

Linking syntactic and semantic arguments in a dependency-based formalism

Abstract: We propose a formal characterization of variation in the syntactic realization of semantic arguments, using hierarchies of syntactic relations and thematic roles, and a mechanism of lexical inheritance to obtain valency frames from individual linking types. We embed the formalization in the new lexicalized, dependency-based grammar formalism of Topological Dependency Grammar (TDG) (Duchier and Debusmann, 2001). We account for arguments that can be alternatively realized as a NP or a PP, and model thematic role alternations. We also treat auxiliary constructions, where the correspondance between syntactic and semantic argumenthood is indirect.

Korean-Chinese Machine Translation Based on Verb Patterns

Abstract: This paper describes our ongoing project "Korean-Chinese Machine Translation System". The main knowledge of our system is verb patterns. Each verb can have several meanings and each meaning of a verb is represented by a verb pattern. A verb pattern consists of a source language pattern part for the analysis and the corresponding target language pattern part for the generation. Each pattern part, according to the degree of generality, contains lexical or semantic information for the arguments or adjuncts of each verb meaning. In this approach, accurate analysis can directly lead to natural and correct generation. Furthermore as the transfer mainly depends upon verb patterns, the translation rate is expected to go higher, as the size of verb pattern grows larger.

WłaŚciwoŚci walencyjne łacinskich przysłówków

Abstract: The paper sought to prove that the valency properties characterize not only Latin verbs, adjectives and nouns, but also Latin adverbs. Since only the valency of adverb as a component of the primary has been given on the list of adverbs which are ascribed by valency properties. On the list there are some adverbs of manner, adverbs of place, adverbs describing number or measure, and also adverbs in the comparative and in the superlative. It is assumed that the valency of the latter adjectives has a syntactic character, in contradiction to the adverbs in the positive which are characterized by the primarily semantic valency.

Valency Lexicon for Czech: From Verbs to Nouns

Abstract: Valency lexicon of Czech verbs has been intensively worked on for more than a year, and now we have at our disposal a detailed description of valency frames of several hundreds verbs. Presently, the challenge naturally arises, to use the existing lexicon for capturing valency of other word classes. In this paper, we focus on valency of nouns derived from verbs. We propose an algorithm for automatic prediction of valency frames of these nouns, and we test it on a sample of data.

Towards a Semantically Motivated Organization of a Valency Lexicon for NLP: The GREG-Proposal

Abstract: The regularity of valency information across entries for different lexical units calls for its generalization. In this paper, we present the results ofour research on the generalization ofsyntactic and semantic valency patterns in German for a mid-size multilingual verbal valency NLP lexicon. We suggest semantic field-oriented multiple inheritance hierarchies. These hierarchies capture fine-grained differentiations between subcategorization frames and allow for a direct relation between case frames and corresponding subcategorization frames. For the implementation, we use the DATR-formalism.

Valency lexicon for Czech: From verbs to nouns

Abstract: Valency lexicon of Czech verbs has been intensively worked on for more than a year, and now we have at our disposal a detailed description of valency frames of several hundreds verbs. Presently, the challenge naturally arises, to use the existing lexicon for capturing valency of other word classes. In this paper, we focus on valency of nouns derived from verbs. We propose an algorithm for automatic prediction of valency frames of these nouns, and we test it on a sample of data.