Showing papers on "Valency published in 1994"

Chemically-defined non-polymeric valency platform molecules and conjugates thereof

Abstract: Chemically-defined, non-polymeric valency platform molecules and conjugates comprising chemically-defined valency platform molecules and biological or chemical molecules including polynucleotide duplexes of at least 20 base pairs that have significant binding activity for human lupus anti-dsDNA autoantibodies.

X‐Ray Absorption Fine Structure Spectra and the Oxidation State of Nickel in Some of Its Oxycompounds

Abstract: The structure of the higher oxide forms of nickel (where Ni has a valency greater than +2) is interesting from the standpoint of developing advanced nickel batteries for consumer applications and for electric vehicle propulsion. Xanes spectra of nickel K-edge and X-ray diffraction patterns of several nickel oxycompounds were measured. The shift in energy of the Ni K-absorption edge toward higher values correlates well with the increase in the oxidation state of nickel from +2 to +4 in the compounds studied. The inflection point energy of the Ni pre-edge structure shifts approximately 1 eV per unit change in valency. The results provide evidence which support the assignment that the valency of Ni in [beta]-NiOOH is +3; Ni[sub 3]O[sub 2](OH)[sub 4] and commercial nickel peroxide (NiO[sub 2]) likewise contain trivalent nickel. The edge shift for quadrivalent nickel in KNilO[sub 6] is reported for the first time.

Group theory in chemistry and spectroscopy : a simple guide to advanced usage

Abstract: Symmetry transformations and groups point groups and their classes representations of point groups crystal field theory for one-electron ion many-electron ions in crystal fields semitempiric crystal field theory theory of directed valency methods of molecular orbitals intensities of optical lines double-groups spin-orbit integration in crystal fields electron paramagnetic resonance exchange interaction in the polynuclear cooordination compounds vibrational spectra and electron-vibrational interactions.

Antitumour activity of tin compounds

Abstract: Tin compounds may be divided into two main classes: (1) inorganic tin salts, in which tin with a valency of +2 or +4 is chemically associated with an element other than carbon, or with an ionic radical; and (2) organotin compounds, which possess one or more direct tin—carbon bond(s).

Effect of Manganese Addition on Phase Stability of Hexagonal BaTiO3

Abstract: Hexagonal BaTiO3 was formed by doping only 2mol% of Mn. Investigation of this effect of Mn in terms of its valency state and size of Mn ion revealed that the small size of Mn4+ ion is a dominant factor favoring the formation of the hexagonal phase.

Study of the valency of rare-earth atoms in the misfit-layer compounds (RS)1+ delta NbS2 (R=La,Ce,Sm) using resonant photoemission and x-ray-absorption spectra.

Abstract: The photoelectron spectrum of (CeS)1.16NbS2 shows a strong resonance enhancement at a photon energy of 120 eV for states with a binding energy of 2.4 eV. The resonance is due to Ce 4d(10)4f1-->4d(9)4f2 transitions, and is evidence that the Ce atoms in this compound have the valency Ce3+ (4f1). The 3d x-ray-absorption spectrum of (LaS)1.14NbS2, (CeS)1.16NbS2, and (SmS)1.19NbS2 exhibit a multiplet structure which is characteristic for La3+ (4f0), Ce3+ (4f1), and Sm3+ (4f5). We conclude that in the misfit-layer compounds (RS)1+deltaNbS2 (R = La,Ce,Sm) the rare-earth atoms are trivalent.

The role of valence interaction in some cation-molecule complexes

Abstract: The role of valence interaction in the 1 : 1 and 1 : 2 complexes between Li + , Na + , Be 2+ , Mg 2+ and CO and N 2 was qualitatively assessed using charge-density-related quantities such as charge transfer, the bond index of the cation-donor atom bond, the valency of interaction and the change in molecular valency calculated at the HF/6–31G ∗ //3–21G level. It has been observed that the relative stability of the complexes can be rationalised on the basis of valence interaction. The molecular hardness parameters have also been calculated. The maximum hardness principle is found to be satisfied in the case of (MCO) n + -(MOC) n+ pairs, and the interaction between (MXY) n + and XY follows the qualitative prediction from the HSAB principle, where M n + is the metal ion and XY is the base.

A wet-chemistry method to determine the Bi and Cu valencies in Bi-Sr-Ca-Cu-O (2212) high-temperature superconductors

Abstract: A spectrometric method is presented to determine the average valency of Bi in Bi2Sr2CaCu2O8+δ high-temperature superconductors (HTSC's) to better than ±0.005. Isostatically pressed samples of varying oxygen content were prepared by sintering in Ar-O2 atmospheres of oxygen partial pressures between 10-5 and 1 bar and temperatures between 300 and 900°C. Bi and Cu valencies were determined by a combination of iodometric titration and the spectrometric method permanganometry. This method takes into account the decay with time of the permanganate concentration in acidic aqueous solution. The latter is determined by light-absorption measurement at λ=526 nm. In the selected sintering regime the Bi valency varies between 3.09 and 3.15, the Cu valency between 2.06 and 2.11. Both Bi and Cu valencies increase linearly with increasing oxygen content δ.

Electronic structure of PrBa2Cu3O7 from LAPW band structure calculations

Abstract: We have performed band structure calculations for PrBa2Cu3O7 using the full-potential LAPW method, which is based on density functional theory. The Pr 4f electrons are treated as valence states and form narrow bands at the Fermi level. Furthermore we have simulated a Pr valency of 3+ (4+) by treating the Pr 4f states as localized states with a fixed occupation of 2 (1). We have determined partial charges, densities of states, difference densities, electric field gradients, and their asymmetry parameters for this system and discuss the differences between the itinerant case and the two model calculations representing the localized f states. The corresponding total energies yield the results that the itinerant f states are the most stable, followed by Pr with a 3+ valency, and the 4+ being the least stable. The overall electronic structure obtained by the itinerant calculation is rather close to the trivalent Pr case.

Thallium valency in superconducting oxides TlBa2Ca1-xYxCu2O7- delta (0<or=x<or=1)

Abstract: Core-level electronic states for TlBa2Ca1-xYxCu2O7- delta (x=0, 0.1, 0.8 and 1.0) are investigated by X-ray photoelectron spectroscopy (XPS). As an effect of yttrium substitution, the Tl core-level shifts toward the higher binding energy side. This implies that electrons donated do not only fill the hole state in Cu-O, but also are partially transferred to the Tl site.

Grammar Learning by a Self-Organizing Network

Abstract: This paper presents the design and simulation results of a self-organizing neural network which induces a grammar from example sentences. Input sentences are generated from a simple phrase structure grammar including number agreement, verb transitivity, and recursive noun phrase construction rules. The network induces a grammar explicitly in the form of symbol categorization rules and phrase structure rules.

Formation of solid-state laser crystal thin film and device for forming solid-state laser crystal thin film

Abstract: PURPOSE:To produce the solid-state laser crystal thin film by heating a substrate in a high-vacuum vessel, supplying a material for forming a laser base material to a substrate surface to grow crystals, simultaneously supplying an active ion species material to the substrate surface and controlling the valency of this active ion species material to the same valency as the valency of the metal ions constituting the crystals of the 'laser base material. CONSTITUTION:The substrate 100 (e.g. alpha-Al2O3) is heated by a halogen lamp 26 in the vessel 10 under a high vacuum and the material (e.g. Al2O3) forming the laser base material is supplied as gas, metal alone or ion or metal compd. to the substrate surface from communicating pipes 12, 14 to grow the crystals on the substrate surface. Further, the active ion species material (e.g. Ti) is supplied from a communicating pipe 16 to the substrate surface simultaneously with the supply of the metal alone or the ions or the metal compd. and the valency of the active ion species material is controlled to the same valency as the valency of the metal ions constituting the crystals of the laser base material. Consequently, the solid-state laser crystal thin film is produced by using the technique like a semiconductor production process.

Die voorsetselwerkwoord in die werkwoordstelsel van Afrikaans

Abstract: There is much confusion concerning the prepositional verb as a separate category main verb in Afrikaans Some linguists are of the opinion that the prepositional verb is not a separate category main verb, but rather a subcategory transitive or intransitive verb There is a definite need for parameters within which the prepositional verb should feature The unique characteristics of the prepositional verb necessitate the need for it to be classified as a separate category, and the need that the relation between the prepositional verb and the particle be highlighted

X-Ray Absorption Fine Structure Spectra and the Oxidation State of Nickel in Some of Its Oxycompounds.

Abstract: The structure of the higher oxide forms of nickel (where Ni has a valency greater than +2) is interesting from the standpoint of developing advanced nickel batteries for consumer applications and for electric vehicle propulsion. Xanes spectra of nickel K-edge and X-ray diffraction patterns of several nickel oxycompounds were measured. The shift in energy of the Ni K-absorption edge toward higher values correlates well with the increase in the oxidation state of nickel from +2 to +4 in the compounds studied. The inflection point energy of the Ni pre-edge structure shifts approximately 1 eV per unit change in valency. The results provide evidence which support the assignment that the valency of Ni in [beta]-NiOOH is +3; Ni[sub 3]O[sub 2](OH)[sub 4] and commercial nickel peroxide (NiO[sub 2]) likewise contain trivalent nickel. The edge shift for quadrivalent nickel in KNilO[sub 6] is reported for the first time.

Valency in a hjemslev-inspired functional grammar substance, form, expression and content in a functional analysis of valency

Abstract: In American generative linguistics as well as in dependency theory the description of valency is assumed to belong at a level of ‘syntactic’ structure, where the distinction between content and expression tends to be lost from view. In the working group on “Danish Functional Grammar” we have tried to carry on the glossematic emphasis on the fundamental status of the distinctions expression vs content and form vs substance (understood in the ‘pure’ substance sense which is sometimes rendered as ‘purport’) and apply them in a functional manner. In particular, we have emphasized the (sometimes underestimated) question of the structuring of semantic content in the clause; it also implies that the structure of the expression plane (word form, larger constituent form, and word order) must be understood in direct relationship with the organization of content. This is also a precondition for a meaningful investigation of the question of iconicity. Some forms of iconicity can be posited on a level of pure...

Dependency-Based Grammatical Information in the Lexicon

Abstract: Dependency grammar offers a suitable basis for including syntactic information into lexical entries, since a crucial point of dependency is the valency of every lexical unit. The valency (or case) frames, or theta grids, are to specify the possible (optional or obligatory) slots occupied by words which accompany a given head. Such a specification may also apply to adverbial and other “free” complementations. With such an approach, the word is understood as one of the central units of language. The class of (basically disambiguated) syntactic representations of sentences can then be specified with using just a small number of general principles to describe the core of grammar.

Ab-initio SCF study of the nature of bonding in neutral and cationic silicon hydrides and analogous carbon compounds

Abstract: The nature of bonding in a number of neutral and cationic silicon hydrides has been studied on the basis of atomic charge (qA), valency (VA), molecular valency (VM) and localised molecular orbitals (LMO). Several structural isomers of each species have been considered. It is found that the most stable isomer is generally associated with maximum qsi and minimum Vsi and VM. Protonation of the neutral hydrides leads to an increase in the positive charge of Si, and in molecular valency. The bonding characteristics of the most stable isomers of the silicon hydrides have been compared with that of analogous hydrocarbons. It has been observed that the difference in bonding stems mainly from the highly electro-positive nature of the Si atom which prefers to form three-centre rather than multiple bonds. The molecular hardness parameters (η) have also been calculated. The most stable isomers of silicon hydrides are generally associated with maximum η. The HSAB principle has been tested by considering some hydrogenation and proton transfer reactions. It is qualitatively satisfied in both cases.