Showing papers on "Valency published in 1987"

Valency and case in computational linguistics

Abstract: In a drawer type ash receiver assembly, a supporting member for a container is formed in a half-box shape from sheet metal by stamping to have opposite-spaced side flanges and a rear end flange flared downwardly and outwardly in one piece therefrom. The supporting member includes a pair of receiving arms extended inwardly from each of the forward ends of the side flanges, and the container includes opposite spaced side rims and a rear end rim which are provided at the outsides thereof with taper surfaces engageable with the flared flanges of the supporting member and of which the side rims are slidably received at the bottom surfaces thereof by resilient means on the receiving arms.

Mixed valency versus covalency in rare-earth core-electron spectroscopy.

Abstract: A comparison of photoemission from shallow core levels with deep core-level spectroscopies allows a distinction between mixed valency and covalency in rare-earth systems. The determinative parameter distinguishing these spectroscopies is the Coulomb interaction between the core hole and the 4f shell. This approach confirms that the compound ${\mathrm{CeF}}_{4}$ is tetravalent, but does not deny the covalent admixture of 4f character into the valence band.

Valence Study of Orthorhombic and Tetragonal Ba2YCu3Oy: The Role of Oxygen Vacancies in High-Tc Superconductivity

Abstract: The valency of Cu ions in the orthorhombic and tetragonal phases of high-Tc superconductor Ba2YCu3Oy (6.22

Local Structure in Orthorhombic and Tetragonal Ba 2 YCu 3 O 7-y : The Role of Oxygen Vacancies for High T c Superconductivity

Abstract: Cu valency and local structure in the orthorhombic and tetragonal phases of high Tc superconductor Ba2YCu3O7-y (0.03

Comparison of atomic charges, valencies and bond orders in some hydrogen-bonded complexes calculated from Mulliken and Löwdin SCF density matrices

Abstract: Atomic charges, valencies and bond orders in six H-bonded systems, (H2O)2, (HF)2 and HnFn+1− (n = 1 to 4) have been calculated using 4-31G, 6-31G* and 6-31G** (only in the case of (HF)2 and HF2−) basis sets and employing definitions based on Mulliken and Lowdin SCF density matrices. The definitions based on the former and the 6-31G* basis set are found to give results in conformity with the classical valence theory. The covalent bonding is highly exaggerated by the alternative definitions based on the Lowdin density matrix. The H-bond formation is found to be accompanied by decrease in total valency, and the valency and atomic charge of bridging hydrogen. A clear distinction between normal and strong H-bonding can be made on the basis of bond order and overlap population of the intermolecular HX (X = F or O) bonds and the amount of charge transferred from the proton acceptor to the donor molecule.

Process for producing electrically insulating regions or layers in or on O ion-conducting solid electrolyte substrates and also composition for carrying out the process

Abstract: There are proposed a process and a composition for producing electrically insulating regions or layers in or on O ion-conducting solid electrolytes doped with trivalent cations or cations of lower valency. The process is characterised in that a suspension or paste containing a compound having one or more pentavalent cations or cations of higher valency is applied to the regions of the solid electrolyte to be electrically insulated and the pentavalent cations or cations of higher valency are allowed to diffuse into the solid electrolyte by heating. The process can be advantageously used if such compounds having pentavalent cations or cations of higher valency are added to suspensions or pastes for, for example, strip conductors or through contacts around which an insulation layer is to be formed during the sintering process. The process can be used particularly advantageously for producing oxygen probes for the determination of the oxygen content in gases, in particular in the exhaust gases of combustion engines.

Distance-transitive graphs of valency five

Abstract: If u and v are vertices of the (finite, connected) graph F, let d(u, v) denote the length of the shortest path joining u to v in F. The graph F is said to be distance-transitive if whenever d(u,v) = d(u',v'), there exists an automorphism g of F such that u = u' and if = v'. Distance-transitive graphs of valency 3 and 4 were originally classified [2, 11, 12, 13] by using a computer to generate all "feasible intersection arrays" (cf. [1, Chapter 20]). In both cases a classification has since been given by hand [4, 5]. We continue this latter tradition and prove the following theorem—which was recently proved independently by Ivanov et al. using a computer [10].

Olefin dimerization method

Abstract: Olefins with between 4 and 24 and preferably between 10 and 20 carbon atoms are selectively dimerized by using zeolite catalysts in acid form which are partially exchanged with salts of metals having a valency of two or more.

The semantic organization of the Serbo-Croatian verb

Abstract: From t h e b e g i n n i n g , s c h o l a r s were te m p te d t o sup p le m e n t t h e in a d e q u a c y o f d e f i n i t i o n s advanced t o a c c o u n t f o r t h e p e r f e c t i v e and t h e i n p e r f e c t i v e v e r b by g r o u p i n g t h e n i n t o s e m a n t i c c a t e g o r i e s , c l a s s e s and s u b c l a s s e s o f t h e two m a jo r c a t e g o r i e s . Then i n 1908 and 1914 A g r e l l s u g g e s te d t h a t t h e r e was a d i f f e r e n c e i n k i n d between t h e two m a j o r c a t e g o r i e s on t h e one hand and t h e i r s u b c l a s s e s on t h e o t h e r . He p roposed t h e te rm A k t i o n s a r t 1th e k i n d o f a c t i o n ' t o be used t o name what he c a l l e d a s e m a n t i c f u n c t i o n o f t h e v e rb w h i c h , a c c o r d i n g t o h im , s p e c i f i e s t h e f a s h i o n i n w h ich an a c t i o n i s p e r f o r m e d , and t h e te rm A sp e k t t o be used e x c l u s i v e l y w i t h r e f e r e n c e t o t h e p e r f e c t i v e and i m p e r f e c t i v e d i s t i n c t i o n . T h i s i n t r o d u c e d new c o m p l e x i t y i n t o an a l r e a d y c o m p l i c a t e d m a t t e r . I t i m m e d i a t e l y r a i s e d t h e q u e s t i o n w h e th e r a s p e c t i s i n t h e domain o f grammar o r l e x i c o g r a p h y , w h e th e r t h e A k t i o n s a r t d i f f e r e n c e i s e q u a l l y i n t h e sphe re 6 Radmila J. Gorup 9783954792269 Downloaded from PubFactory at 01/10/2019 04:17:57AM via free access o f b o th t h e p e r f e c t i v e and t h e i n p e r f e c t i v e v e r b o r o n l y t h e p e r f e c t i v e , e t c . , e t c . More abou t t h e s t a t u s o f A k t i o n s a r t ( e n ) i n t h i s a n a l y s i s w i l l be s a id i n Appendix A. I n a dva nc ing d e f i n i t i o n s w h ich appeared i n t h e f i r s t h a l f o f t h e t w e n t i e t h c e n t u r y , t h e a n a l y s t s were u s u a l l y n o r e conce rned w i t h d e f i n i n g the p e r f e c t i v e a s p e c t . The i n p e r f e c t i v e aspec t was g e n e r a l l y d e f i n e d n e g a t i v e l y . As s t a t e d i n F e r r e l l ( 1 9 5 1 ) , t h e r e are f i v e n a in d e f i n i t i o n s o f v e r b a l a s p e c t t h a t a t one t i n e o r a n o th e r have r e c e i v e d the a t t e n t i o n o f s c h o l a r s . The f i r s t and t h e n o s t e n d u r i n g one was t h e d e f i n i t i o n a l r e a d y m en t ioned a c c o r d i n g t o wh ich t h e p e r f e c t i v e a s p e c t e x p r e s s e s an a c t i o n as com p le ted w h i l e t h e i n p e r f e c t i v e v e rb e x p re s s e s an a c t i o n as e n d u r i n g , as d e v e l o p i n g i n t i n e . One o f t h e e l a b o r a t i o n s o f t h i s th e n e was t h a t th e o p p o s i t i o n between t h e p e r f e c t i v e and t h e i m p e r f e c t i v e a s p e c t l i e s a lon g t h e p a ra m e te r o f d u r a t i o n . A c c o r d in g t o t h i s v i e w , i n the p e r f e c t i v e v e rb t h e a c t i o n i s denoted i n r e l a t i o n s h i p t o a l i m i t e d t i n e , e i t h e r l o n g o r s h o r t . In t h e i m p e r f e c t i v e v e rb t h e a c t i o n i s re g a rd e d w i t h o u t r e l a t i o n s h i p t o any l i m i t a t i o n i n t i m e . The c h i e f exponent o f t h i s v ie w was F o r t u n a t o v and h i s a n a l y s i s i n f l u e n c e d B e l i e and many o t h e r S e r b o C r o a t i a n i s t s . O the r e xpo n e n ts o f i t were Kosch m iede r , Sorensen and o t h e r s . A n o th e r a t t e m p t t o im p rove on t h e o r i g i n a l d e f i n i t i o n Radmila J. Gorup 9783954792269 Downloaded from PubFactory at 01/10/2019 04:17:57AM via free access

Mixed Valence in Chemistry

Abstract: Mixed valence is as old as chemistry itself, Prussian blue, Fe4 [Fe(CN)6]3 14H2O and magnetite, Fe3O4, being well-known examples. Mixed valence chemistry comprises a variety of solids formed by a third of the elements in the periodic table and the subject has assumed great importance in recent years1,2. Since variable valency is a prerequisite, the phenomenon is found in compounds of transition elements, lanthanides and some of the elements with stable s2 and s0 configurations (e.g. Sn, Sb, Tl, Bi). Mixed valence compounds that chemists ordinarily deal with exhibit formal oxidation states of a metal ion differing by one or two units (as in Fe3O4) and are distinct from systems such as Ce and SmS involving a fluctuation in the electronic configuration between fnd0 and fn−1 d1 states. Mixed valency is readily recognized by the chemical formula itself (Pb3 O4, TinO2n−1), but there are solids which show apparent integral oxidation states. Examples of the latter are Sb2 O4 (Sb3+ Sb5+ O4) and Ba Bi O3 (Ba Bi 0.5 3+ Bi 0.5 5+ O3). Many metal chain compounds and metal complexes also exhibit mixed valence. In this paper, we shall briefly discuss different classes of mixed valence compounds studied by chemists to show how the rate of electron transfer plays a crucial role. We shall examine a few oxide systems whose properties in the solid state are determined by the electron transfer mechanism.

Europium valency in EuCu2−x Fe x Si2, EuCu2Si2−x Ge x , EuCu2−x Si2+x and EuNi2−x Si2+x

Abstract: Mossbauer spectroscopy, X-ray photoemission spectroscopy and magnetization studies of EuCu2−xFexSi2, EuCu2Si2−xGex, EuCu2−xSi2+x, and EuNi2−xSi2+x have been performed In EuFe2Si2 and EuNi2Si2 the Eu ion is trivalent, in EuCu2Si2 it is of intermediate valency In all systems withx=0, many inequivalent Eu sites of intermediate valency are formed In EuCu2−xFexSi2, the average valency of Eu moves nonmonotonically toward Eu3+ In EuCu2Si2−xGex, EuCu2−xSi2+x and EuNi2−xSi2+x, the Eu average valency moves quickly towards Eu2+ In all three systems, whenx=1, all Eu ions are already stable divalent The systems EuCuSi3 and EuNiSi3 order magnetically at 40 K and 34 K, and exhibit hyperfine fields of 323 kOe and 458 kOe, respectively XPS and Mossbauer isomer shift determinations of the average Eu valence as a function of temperature in EuCu15Fe05Si2 are in good agreement The experimental observations concerning the Eu valencies can not be explained solely in terms of the local volume available to the Eu ion; the nature of chemical environment plays a dominant role

Topological aspects of chemical reactivity: valency changes in the course of chemical reactions

Abstract: The Jug and Gopinathan approach to the use of valency changes for the characterization of chemical reactions is generalized by incorporating it into the framework of the recently proposed topological description of chemical reactivity in terms of the overlap determinant method. The conclusions of the simple topological analysis agree with the results of the direct quantum chemical treatment, indicating thus that the overlap determinant method depicts correctly the principal features of the electron density reorganization occuring during the chemical reactions. One of the fundamental concepts of organic chemistry is the concept of valency, on the basis of which an immense number of empirical findings accumulated by the classical structural theory could be classified and systemized. For a deeper justification of this theory, frequent attempts have been made over the past decade to incorporate the valency concept into the wider scope of the theoretically founded quantum chemical description of molecular structure. The first to attempt at such generalization were probably Armstrong and coworkers1 who defined the valency within the CNDO approximation in terms of the so-called Wiberg index2 • Although this .original definition was later extended to more sophisticated semi empirical and ab initio techniques in both orthogonal and nonorthogonal basis sets 3 - 10, the basic idea of all such generalizations remains virtually unchanged. The most significant consequence arising from this quantum chemical generalization concerns the fact that the valency no longer needs to attain, as in the classical theory, only integer values. Nevertheless, the calculated valencies, at least in the case of usual molecules, approach the classical integer values rather closely. The advantage of the quantum chemical generalization thus appears above all for various special structures such as the hypervalent clusters CLi6 , OLi4 , OLi6 , etc., where the classical description completely fails, whereas the new definition allows us to obtain a sufficiently iIlustrative picture of bonding. Similar complications can also occur for various nonclassical structures which may appear as intermediates or transition states in chemical reactions. In view of the successful application of the valency concept to the description of hypervalent structures, Gopinathan and JugU - 13 have recently proposed its use also to the characterization of the above nonclassical species. Stimulated by the interesting results of these studies we suggest in this paper a modification of the original approach by incorporating the valency concept into the framework of the recently formulated description of chemical reactivity in terms of the generalized overlap determinant method.

Electronic structure calculations for high-Tc oxides

Abstract: Band-structure calculations with the full-potential linear augmented plane wave method were performed for the high-Tc related oxides, La2CuO4 and YBa2Cu3Oy with y = 6 and 7. Implications of the calculated results are discussed in relation to Cu valency and photoemission experiments.

A valency method for the prediction of geometry of molecular excited states

Abstract: A simple method, based on the concept of molecular valency and making use of the virtual orbitals of the ground state, is proposed to predict the geometry of molecules in various excited and ionised states. The method is found to be accurate for bond angle predictions.

ESR dating utilizing change in valency or ligand of transition-metals

Abstract: A physicochemical dating method which utilizes changes in valency or ligand of transition metals by various physical and chemical processes is proposed. We have successfully applied this method to the dating of a biological material of coagulated blood by detecting the change of the ligand of heme-iron with ESR. This method may be useful for dating not only bilogical materials but also minerals and fossils in earth sciences.

Magnetic Susceptibility of YbCuGa, YbAgGa and YbAuGa Compounds

Abstract: The rare earth ions normally exist in a trivalent state in most of their alloys and compounds. However, Ce, Sm, Eu, Tm and Yb are exceptions and can exist in other than the trivalent state. Thus cerium can have a valency of four and Sm, Eu, Tm and Yb a valency of two. The valence adopted by these rare earth ions in an alloy or a compound is a function of several factors such as nature of other alloying elements, temperature, pressure etc. In some systems, there may be a rapid fluctuation between the two valence states. Such systems are characterized [1] by the anomalies in the unit cell volume, maxima in the susceptibility, large electronic specific heat coefficient, two sets of lines in the XPS spectra corresponding to two different initial state configurations of the rare earth ion etc.

The roots of the plural action verb in the dravidian languages

Abstract: Study of the plural action verb reveals how it reflects general principles of comparative Dravidian grammar. A new synchronic analysis serves as the basis of a new etymology of this form in South-Central Dravidian. It is shown to be descended from the echo compound verb through a series of elementary steps. Compound Verb Contraction is first applied to the echo compound verb, creating a synthetic form out of an analytic one. Subsequent restructuring brings this contracted form into line with the morphological and lexical constraints on the words in these languages. The formal and semantic correspondences are presented and explained in detail. The new etymology entails rejecting the reconstruction of a system of verb stem derivation to Proto-Dravidian. It also illustrates the extent to which emotive language such as the echo compound verb is integrated into the grammar of the Dravidian languages, and participates in their historical development.

Production of photomagnetic recording medium

Abstract: PURPOSE:To form a photomagnetic recording layer having an excellent storage environment characteristic and uniform quality with low medium noise on a substrate with good reproducibility by introducing the raw material for forming the photomagnetic recording layer expressed by the specific formula and active species into a film forming chamber and causing a chemical reaction. CONSTITUTION:The compd. of the raw material for forming the photomagnetic recording layer expressed by the formula RnMm and the active species making the chemical reaction with said compd. is introduced into the film forming chamber and the photomagnetic recording layer is formed on the substrate. In the formula, M is a transition metal element or rare earth metal element (Fe, Co, Ni, Gd, Tb, Dy, etc.), R is hydrogen, halogen, hydrocarbon group, m is equal to the valency of R or the positive integer of the integer times said valency, n is equal to the valency of M or the positive integer of the integer times said valency. The active species are generated by applying thermal energy by hydrogen, etc., and the proportion of the compd. and the active species is preferably about 1,000:1-1:10 (introducing flow rate ratio). The internal pressure of the film forming space is preferably about 1X10 -5X10 PA.

Investigation of the electromigration of tritium in tantalum

Abstract: The diffusion and electromigration of tritium in TaHT systems in α and ϵ phases has been investigated. The diffusion coefficient and the ratio of the effective valency to the thermodynamic factor ƒ were determined from radioactivity measurements of tritium. It has been found that during the phase transformation α → ge the effective valency changes in sign from positive to negative.

Valency relations between alkali and alkali earth elements and elements of second and third long periods

Abstract: Elements of groups IA and IIA form many compounds with elements of the third long period passing back from bismuth to platinum; fewer compounds are formed with elements of the second and earlier periods. The incidence of such compounds has been analysed graphically such that the valencies on the components may be inferred. The compounds exhibit low valency on the second/third long period component, and normal valency on the A-element. The compounds are covalent in character, and are formed across the ionic divide consistent with Fajans' rule.MST/464