NP Coordination Research Articles

Synthesis and Crystal Structures of Volatile Neptunium(IV) β-Diketonates.

Production of certified reference materials in support of domestic nuclear forensics programs require volatile precursors for introduction into electromagnetic isotopic separation instruments. β-Diketone chelates of tetravalent actinides are known for their high volatility, but previously developed synthetic approaches require starting material (NpCl4) that is prohibitively difficult and hazardous to prepare. An alternative strategy was developed here that uses controlled potential electrolysis to reduce neptunium to the tetravalent state in submolar concentrations of hydrochloric acid. Four different β-diketone ligands of varying degrees of fluorination were reacted with an aqueous solution of Np4+. Products of this reaction were characterized via X-ray diffraction and infrared spectroscopy, and were found to be neutral 8-coordinate complexes that adopt square antiprismatic crystal geometry. Synthesis of Np β-diketonates by this approach circumvents the necessity of using NpCl4 in tetravalent Np coordination compound synthesis. The volatility of the complexes was assessed using thermogravimetric analysis, where the temperature of sublimation was determined to be in the range of 180° to 205 °C. The extent of fluorination did not appreciably alter the sublimation temperature of the complex. Thermal decomposition of these compounds was not observed during sublimation. High volatility and thermal stability of Np β-diketonates make them ideal candidates for gaseous introduction into isotopic separation instruments.

Structure, spectra, and photoinduced electron-redistribution properties of TiO2/organic copolymers with gold nanoparticles. A DFT study

The structural, thermodynamic and spectral properties of photocatalytically active composite copolymers of polytitaniumoxide and hydroxyethyl methacrylate TiO2/HEMA and the copolymers with incorporated gold nanoparticles (AuNPs) TiO2/HEMA/Au have been studied using the DFT and TD-DFT theories (B3LYP/LANL08(Au)/6-31G(d,p)). Molecular clusters of TiO2 with the chemically linked residues of HEMA were considered as copolymer models containing various structure motifs, such as linear chains, double bonds, tetrahedral, cubic and octahedral TiO2 fragments. The AuNPs incorporation was modeled by Au atoms and Au7 clusters coordinated at various positions of the TiO2/HEMA copolymer. The effect of cluster structure and Au coordination modes on thermodynamic characteristics, IR spectra, electronic excitation spectra and the photoinduced electron redistribution has been analyzed on the basis of comparison with the experimental IR and UV spectra. The results demonstrate the influence of various structural features and NP coordination modes on photocatalytic properties, which is important for the synthesis of copolymers with required characteristics.

Elmo's Sister's Ball: The Problem of Acquiring Nominal Recursion

Recursion is the ability to iterate syntactic constituents inside constituents. Experimental and corpus literature indicates that comprehending recursive structures is difficult for children. Since recursion is a fundamental property of language, the result of the application of core minimal tools (merge, label, and select), why does it present an acquisition challenge? We propose that while Merge itself is universal, its application is determined by selection, which is extensively parameterized. We investigate whether children's difficulties can be defined in terms of the complexity of the selectional demands involved. This investigation leads to three empirical questions: i. How does NP recursion compare to NP coordination in acquisition? ii. Do children acquire each level of recursion independently or is recursion triggered automatically once the initial selectional requirements are acquired? iii. Are there differences in the acquisition of different types of nominal recursion? We compare the selectional requirements of English genitives, PPs, and NP coordination. Our syntactic analysis suggests that genitive recursion has more complex selectional demands than PP recursion. We designed a study eliciting production of two level embedded prepositional and genitive NPs. Preschool-aged English-speaking children (n = 46) and adults (n = 11) participated in an elicitation study. Children were comparable to adults in their ability to produce three coordinated NPs, but had substantial difficulty linking three NPs using recursion. First- and second-level embedding were clearly distinct steps in development. These findings have implications for the independence of phrasal and selectional development in children and for our understanding of structural complexity in child language and in theory.

Structure of the double formate KNpO2(OOCH)2

KNpO2(OOCH)2 was isolated from neutral Np(V) solutions with a high concentration of potassium formate. The crystal structure of this compound was determined. The structure consists of infinite anionic chains [NpO2(OOCH)2] − . Potassium cations are located between these chains. The Np coordination polyhedron is a hexagonal bipyramid whose equatorial plane is formed by the oxygen atoms of four HCOO− ions. The Np bipyramids in the chains are bound via common equatorial edges. The anionic chains in the structures of KNpO2(OOCH)2 and NH4NpO2(OOCH)2 studied previously have similar composition but different structure.

Crystal Structure of a Double Oxalate of Np(V) and Co(NH3) 6 3+ , Co(NH3)6NpO2(C2O4)2·1.5H2O

The crystal structure of a dioxalate complex Co(NH3)6NpO2(C2O4)2·1.5H2O was studied. The structure consists of centrosymmetrical dimeric anions [NpO2(C2O4)2] 2 6− , [Co(NH3)6]3+ cations, and water molecules of crystallization. The NpO 2 + dioxocations have close Np-O bond lengths (average 1.824 A) and are noticeably bent (ONpO angle 175.6°). Each dioxocation in the [NpO2(C2O4)2] 2 6− anion is surrounded by five oxygen atoms of three C2O 4 2− anions; the Np coordination polyhedra are pentagonal bipyramids sharing a common edge.

An HPSG account of closest conjunct agreement in NP coordination in Portuguese

This paper discusses the NP-internal agreement strategies observed in an empirical (corpus based) study of Portuguese, and proposes an analysis which is formalized in the framework of Head-Driven Phrase Structure Grammar (HPSG). The empirical study suggests that what were previously thought to be rare or non-existent strategies occur with surprising frequency. Capturing these strategies poses problems for many standard approaches to agreement. The formalization shows how they can be captured with a relatively conservative extension of the existing HPSG theory of agreement.

X-ray absorption spectroscopy studies of reactions of technetium, uranium and neptunium with mackinawite

Technetium, uranium and neptunium may all occur in the environment in more than one oxidation state (IV or VII, IV or VI and IV or V respectively). The surface of mackinawite, the first-formed iron sulfide phase in anoxic conditions, can promote redox changes so a series of laboratory experiments were carried out to explore the interactions of Tc, U and Np with this mineral. The products of reaction were characterised using X-ray absorption spectroscopy. Technetium, added as TcO 4 −, is reduced to oxidation state IV and forms a TcS 2-like species. On oxidation of the mackinawite in air to form goethite, Tc remains in oxidation state IV but in an oxide, rather than a sulfide environment. At low concentrations, uranium forms uranyl surface complexes on oxidised regions of the mackinawite surface but at higher concentrations, the uranium promotes surface oxidation and forms a mixed oxidation state oxide phase. Neptunium is reduced to oxidation IV and forms a surface complex with surface sulfide ions. The remainder of the Np coordination sphere is filled with water molecules or hydroxide ions.

Neptunium redox speciation

Insights about the redox speciation of neptunium in an aqueous mineral acid electrolyte were obtained through a combination of in situ EXAFS (extended X-ray absorption fine structure) spectroelectrochemistry, density functional theory (DFT), and simple geometric modeling. A single solution of neptunium in 1 M perchloric acid was used to extract metrical information about the Np coordination environment, in terms of hydration numbers (n) and Np-O interatomic distances. Four aquo ions - Np3+·nH2O, Np4+· n´H2O, [Np5+O2]+· n´´H2O, and [Np6+O2]2+· n´´´H2O - were electrolytically prepared and precisely maintained by use of constant potential bulk electrolysis (with coulometry) throughout the simultaneous EXAFS data acquisition. For the Np(III) and Np(IV) aquo ions, the experiments revealed a contraction of the average Np-O bond lengths from 2.48(2) to 2.37(2) Å, respectively. The data analyses suggest that there are 9 water molecules in the first or inner hydration sphere about Np3+in [Np(OH2)9]3+and Np4+in [Np(OH2)9]4+. The DFT calculations reveal 8-9 water molecules coordinated to Np(III), supporting the EXAFS results. Simple geometric modeling supports a coordination number of 8 for both trivalent and tetravalent Np. For the Np(V) and Np(VI) aquo ions, the EXAFS revealed bond length contractions. The average interatomic distances for the trans-dioxygen atoms in [NpO2]+and [NpO2]2+decreased from 1.80(2) Å for Np(V) to 1.73(2) Å for Np(VI). The average interatomic distances to the oxygen atoms of the coordinated H2O molecules decreased from 2.44(3) Å to 2.36(3) Å, respectively. The oxygen coordination numbers were identical, suggesting that 5 water molecules are bound to Np5+in [NpO2(OH2)5]+and to Np6+in [NpO2(OH2)5]2+.

A unified semantic treatment of singular NP coordination

L'A. examine l'interpretation de and dans les coordinations de SN, en relation avec le statut transcategoriel de ce morpheme et se focalise sur la distinction problematique entre les interpretations collectives et distributives. Il propose une theorie unifiee de la coordination, permettant de traiter les conjonctions and uniformement d'une maniere standard comme des intersections, afin de rendre compte egalement des conditions de verite des predications collectives comme Mary and John met. Dans cette optique, il examine d'abord les coordinations de noms propres, puis discute de la hierarchie des operateurs pour l'interpretation des SN et etend sa theorie aux SN quantifies singuliers

Comitative coordination: A case study in group formation

This paper argues that in Russian a (singular) NP can combine with a comitative PP to form a complex plural NP, and that this NP denotes a group in the sense of Landman (1989). A single-headed GPSG analysis of the construction is proposed and argued for, and the implications of the analysis for number agreement are discussed. The semantic properties of the construction (and its counterpart in Polish) are subsequently detailed and are compared with those of ‘ordinary’ NP coordination; the preliminary conclusion is that the construction differs both in denotation and in conventional meaning from NP coordination.

NP COORDINATION IN MEDIEVAL CHINESE: A DISCOURSE APPROACH

This paper deals with the historical development, from a discourse perspective, of nominal (NP) coordination from Early Medieval Chinese, as reflected in Shishuo Xinyu 世说新语 to Late Medieval Chinese, as reflected in Dunhuang Bianwen 敦煌变文 It is shown that simple juxtaposition (or zero form) is the basic device used throughout Medieval Chinese. Conjunctions are found to appear with conjuncts that are either non-specific, or specific but sub-dividable in terms of discourse context and conception. The distinction between coordination and comitatives is maintained through a comparison of a cluster of discourse properties such as anaphora, topicality and empathy, as exhibited in the NPs of the two constructions. We show that the most prominent development from Early Medieval Chinese to Late Medieval Chinese is the grammaticization of sub-dividability. Based on the observation that unitary NPs tend to be expressed with simple juxtaposition and distant NPs overt conjunction, we propose the iconicity principle to account for the grammar of NP coordination in Medieval Chinese.

NP coordination in Medieval Chinese : a discourse approach

NP coordination in Medieval Chinese : a discourse approach

Feature percolation, unary features, and the coordination of English NPs

SGWW's adoption of unary features creates a range of problems. The general problems affecting feature percolation can be cured by minor redefinitions of the relevant principles. But if we wish to maintain SGWW's attractive position that the syntax of coordination depends on fully general principles which extend directly to cover person categories in NP coordination, while the distinctive behaviour of number in such coordination follows from properties of the phrases which introduce specific conjunctions, then something further is required. A straightforward solution, which will have implications for the treatment of person, number and gender in other languages, is to retain orthodox features with more than one value and modify the scope of feature percolation by permitting the Head Feature Convention to hold for specific, probably unmarked, feature values. This imports the intended effect of unary feature specification into the workings of feature percolation.

Coordination schema and chinese NP Coordination in GPSG

Dans cet article, nous étudions la coordination des SN chinois, dans le cadre de la GPSG de Sag, Gazdar, Wasow, et Weisler (1984). La théorie de ces auteurs ne permet pas de rendre compte de la conjonction en mandarin, dans laquelle, tous les SN, sauf le premier, peuvent être attachés librement à une conjonction. Nous proposons de réviser la théorie sur deux points : tout d'abord, en introduisant des énoncés sur la precedence linéaire exprimant des implications existentielles , et ensuite, en permettant à [CONJ] d'avoir plusieurs valeurs concurrentes. Nous montrons que ces révisions rendent compte de manière satisfaisante des données du chinois et des cas d'exception de l'anglais.