bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ab initio study of the ammonia–ammonia dimer: BSSE‐free structures and intermolecular harmonic vibrational frequencies
Authors: Bende A. , Vibók Á. , Halász G. J. , Suhai S. 
Published: June 2004

AbstractThe influence of basis set superposition error (BSSE) in optimized geometries, force constants and intermolecular harmonic vibrational frequencies of the ammonia–ammonia dimer have been studied both at the Hartree–Fock and correlated (second‐order Møller–Plesset perturbation theory) levels of theory using several different basis sets as (6‐31G, 6‐311G, 6‐31++G, 6‐311++G, 6‐31G(d,p), 6‐311G(d,p), 6‐31++G(d,p) 6‐311++G(d,p) and 6‐311++G(2d,2p)). The widely used a posteriori Boys–Bernardi “counterpoise” (CP) correction scheme has been compared with the a priori method utilizing the chemical Hamiltonian approach (CHA). The results show that practically there is no difference between these two methods, so the a priori CHA scheme can be considered as an ultimate solution of the BSSE problem. It is also concluded that the BSSE influence is very significant, so removing this effect is very important. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Recoordination of a metal ion in the cavity of an arylazacrown ether: Model study of the conformations and microsolvation of calcium complexes of arylazacrown ethers
Authors: Freidzon A. Ya. , Bagatur'Yants A. A. , Gromov S. P. , Alfimov M. V. 
Published: June 2004

AbstractPhotoinduced recoordination of Ca2+ complexes of photochromic azacrown ethers is studied by the density functional method using model arylazacrown ethers and a real azacrown‐containing styryl dye. Two types of previously found conformations of the crown ether–calcium complexes, axial and equatorial, are studied, taking into account water molecules in the first coordination sphere of the cation. It is found that the first coordination sphere of the cation contains no more than three water molecules, the fourth one belonging to the second coordination sphere. The presence of three or four water molecules in the coordination sphere of the cation decreases relative energies of the conformations with broken metal–nitrogen bond, thus favoring metal recoordination. In the azacrown‐containing styryl dye, this leads to the ground‐state equilibrium (i.e., tautomerism) between the axial and equatorial forms of the complex. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Structure and vibrations of the CF3NO molecule in the ground and lowest excited electronic states: A test of ab initio methods
Authors: Dolgov Eugeniy K. , Bataev Vadim A. , Pupyshev Vladimir I. , Godunov Igor A. 
Published: June 2004

AbstractEquilibrium geometries, harmonic vibrational frequencies, and barriers to internal rotation of the CF3NO molecule in the ground singlet (S0) and lowest excited triplet (T1) and singlet (S1) electronic states are calculated using various ab initio techniques and compared with the experimental data. The sensitivity of the results to the choice of atomic orbital basis set, in particular, to the presence of f‐symmetry functions, and to the dynamical correlation treatment is analyzed. Anharmonic vibrational frequencies and dipole moment of the CF3NO molecule in the ground state are computed. The results of all approaches employed are in good agreement with each other and with available experimental data. Conclusions concerning the accuracy of different methods are drawn. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Bryophytes as a special mesohabitat for meiofauna in a rip‐rapped channel
Authors: Linhart Jakub , Vlčková Šárka , Uvíra Vladimír 
Published: June 2004

AbstractRock rip‐rap is commonly used by river engineers for bank stabilization. However, there is a general lack of information on invertebrate communities inhabiting these structures. This study examines the permanent and temporary meiofauna dwelling in dense clumps of an aquatic moss Fontinalis antipyretica growing on rock rip‐rap along a side channel of the Morava river, Czech Republic. We estimated the amount of fine particulate matter (total trapped matter, TM) trapped in the moss as both a habitat and food source for meiofauna. Total mean numbers of the moss‐dwelling meiofauna per 10 g dry weight of moss and 1 m2 of the bottom area were 253 917 ± 178 335 (mean ± SD) and 7 160 461 ± 5 029 047 individuals, respectively, during October 1999–November 2000. Out of 20 operational taxonomic units, Bdelloidea was the dominant group with about 76% of the total meiofauna numbers followed by Monogononta (11.23%), Nematoda (6.38%), Chironomidae (4.08%) and Oligochaeta (1.06%). Coarse trapped matter (500–1000 µm) contributed about 4% to the total, medium TM (100–500 µm) around 14% and the finest TM (30–100 µm) 82%. Organic matter (OM) forms 10% of the total TM. The seasonal variations in TM, OM and mineral matter and their size fractions have significantly correlated (Spearman rank correlation coefficient, P < 0.05 or 0.01) with densities of Oligochaeta, Hydrachnidia, Cladocera, Harpacticoida, nauplii of Copepoda, Chironomidae. In regulated channels, rock rip‐rap overgrown by aquatic bryophytes is desirable because it increases the spatial diversity of habitats and supports considerably higher numbers of meiofauna compared to the gravel bed and may substantially contribute to the stream metabolism. Copyright © 2002 John Wiley & Sons, Ltd.
Macroinvertebrate community structure in a regulated river segment with different flow conditions
Authors: Cortes Rui Manuel Vitor , Ferreira Maria Teresa , Oliveira Simone Varandas , Oliveira Daniel 
Published: June 2004

AbstractTwo types of modification of the hydrological system are present in the same regulated segment of the Lima River (NW Portugal): (a) a reduced and constant flow from hypolimnetic release; (b) an intense irregular flow (daily and seasonal). Using multivariate techniques it was possible to compare the effects of these two kinds of disturbance on the macroinvertebrate communities. The communities colonizing both sites exhibited a higher variation in composition and diversity when compared to undisturbed sites. However, such variability was even more evident in the first case, in spite of the stability of the environmental conditions. Such temporal replacement of species is linked to the dominance of tolerant taxa with short life cycles. In the regulated segment the poor water quality and the lack of litter input impacted mainly on the shredders group. This work shows the failure of the practice of releasing constant flows as an attempt to mitigate regulation impacts. Copyright © 2002 John Wiley & Sons, Ltd.
The effect of Keepit Dam on the temperature regime of the Namoi River, Australia
Authors: Preece Russell M. , Jones Hugh A. 
Published: June 2004

AbstractModifications to water temperature caused by the release of hypolimnetic water from thermally stratified reservoirs pose a major threat to the aquatic biota of lowland rivers in Australia's Murray–Darling basin. Keepit Dam is earmarked as one of several deep‐release structures in the basin causing ecologically significant temperature modification over a large length of river. This study utilized discrete and continuously monitored historical water temperature data from stream gauging stations, together with reservoir thermal profile data, to assess the impacts of Keepit Dam on the thermal regime of the Namoi River. Modifications to selected components of the river's annual temperature cycle were quantified in relation to a pre‐dam temperature regime estimated from statistical models incorporating catchment, hydrological and sample attributes. Keepit Dam has modified the thermal regime of the Namoi River. The effect was greatest immediately downstream from the dam where the annual maximum daily temperature was approximately 5.0 °C lower and occurred three weeks later than the pre‐dam condition. This change was sufficient to disrupt thermal spawning cues for selected Australian native fish species. The magnitude of disturbance progressively diminished with distance from the dam. Key aspects of the river's annual temperature cycle were largely restored to the pre‐dam condition within 100 river km downstream from the dam, which is closer than previous estimates. However, there was marked inter‐annual variation in the magnitude of thermal modification and ecological impact as a result of year to year changes in tributary flow and reservoir behaviour. Copyright © 2002 John Wiley & Sons, Ltd.
Physical habitat structure in Danish lowland streams
Authors: Pedersen Morten Lauge , Friberg Nikolai , Larsen Søren Erik 
Published: June 2004

AbstractDredging or channelization has physically modified the majority (90%) of the 64 000 km of Danish stream network with substantial habitat degradation as a result. Analyses of physical habitat structure in streams, biota, catchment features and regional differences in hydrology, topography and geology have never been carried out in Denmark. Therefore, there is little knowledge of processes, interactions and patterns across the different scales. Physical habitats, catchment parameters and macroinvertebrates were sampled at 39 sites in three major river systems during summer and winter 1993.In‐stream physical conditions and catchment attributes affect the physical habitat structure in Danish lowland streams. Local differences in hydrology, land use, catchment topography and soil types correlated to the in‐stream physical habitat parameters. Local differences in hydrology and topography resulted in a separation of the Suså streams with respect to physical habitats. Mud deposition was pronounced at sites with low discharge and low near‐bed current velocity. Low mud cover was primarily associated with streams with high discharge located in pristine catchments. Stability in the streams was therefore closely linked to in‐stream deposition of fine sediment. Generally, macroinvertebrate community diversity increased as discharge increased. Mud cover negatively affected macroinvertebrate diversity and EPT taxon richness.Regional physical habitat structure and macroinvertebrate community structure were primarily associated with local variations in hydrology, geology and topography. Low‐energy streams were primarily located in the Suså river system and the high‐energy streams in the Gudenå and Storå river systems, leading to extensive deposition of mud during summer. Streams in the Suså river system generally had lower diversity and species richness compared to the streams in the Gudenå and Storå river systems.Hydraulic conditions and substratum dynamics in streams are important when managing lowland streams. This study therefore analysed interactions and parameter correlations between physical habitats, stream stability and catchment attributes as well as macroinvertebrate community structure across multiple scales. Copyright © 2004 John Wiley & Sons, Ltd.
Teaching future K‐8 teachers the language of Newton: A case study of collaboration and change in university physics teaching
Authors: Briscoe Carol , Prayaga Chandra S. 
Published: June 2004

AbstractThis interpretive case study describes a collaborative project involving a physics professor and a science educator. We report what was learned about factors that influenced the professor's development of teaching strategies, alternative to lecture, that were intended to promote prospective teachers' meaningful learning and their use of canonical ways of communicating physics concepts. We describe how the professor's beliefs influenced the pedagogy that he used to communicate the language of physics and the nature of what was communicated. We also report how our collaboration fostered change as we developed a shared language that allowed us to discuss how students learn and to explicate the referent beliefs that supported the professor's practices. We found that focused reflection on referent beliefs led to a change in the manner in which the professor communicated with the prospective teachers. Traditional lecture pedagogy focused the professor's concern on how he was teaching evolved toward a pedagogy that focused on how students were learning. Classroom interactions were increased with a primary goal of orchestrating a discourse of physics initiated in the language already accessible to the prospective teachers. This change in the manner that classroom interactions occurred provided opportunities for the prospective teachers' language to evolve toward eventually communicating their ideas in canonical physics language. © 2004 Wiley Periodicals, Inc. Sci Ed 88:947–969, 2004
Implications and applications of folk zootherapy in the state of Bahia, Northeastern Brazil
Authors: Costa‐Neto Eraldo Medeiros 
Published: June 2004

AbstractThis paper deals with the use of 180 animal species as medicinal resources in the state of Bahia, Northeastern Brazil. Data, which come from field works carried out in different indigenous, traditional, rural and urban communities within Bahia State, were gathered through the compilation of information available in scientific articles, monographs, theses, reports and presented papers. The animal‐based folk medicines come from millipedes (0.5%), annelids (1.0%), amphibians (1.0%), arachnids (1.0%), echinoderms (1.5%), crustaceans (4.0%), molluscs (6.0%), reptiles (12.0%), birds (13.0%), fishes (17.0%), mammals (20.0%) and insects (23.0%). These bioresources provide about 300 raw materials, which are turned into medicines and prescribed to treat a wide range of locally diagnosed ailments. The result shows how important this ethnozoological phenomenon is, and indicates that traditional knowledge on zootherapy is to be seriously studied in order to lead to the discovery of new sources of drugs. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment.
Federal and State Aid in the 1990s: A Policy Context for Enrollment Management
Authors: Ort Shirley A. 
Published: June 2004

AbstractThe demographic, social, and economic forces of the 1990s dramatically altered the higher education operating environment. This chapter provides a policy context within which to consider the emergence of enrollment management in higher education in response to these forces, and calls for a research‐ and policy‐based approach to enrollment management in the future.
Conditioned slicing supports partition testing
Authors: Hierons Rob , Harman Mark , Fox Chris , Ouarbya Lahcen , Daoudi Mohammed 
Published: June 2004

AbstractThis paper describes the use of conditioned slicing to assist partition testing, illustrating this with a case study. The paper shows how a conditioned slicing tool can be used to provide confidence in the uniformity hypothesis for correct programs, to aid fault detection in incorrect programs and to highlight special cases. Copyright © 2001 John Wiley & Sons, Ltd
Teaching Key Competencies in Liberal Arts Education
Authors: Goldenberg Edie N. 
Published: June 2004

AbstractThe study of the liberal arts provides an exemplary arena for students to become active learners. The complexity of modern society requires a broader understanding of societal problems rather than a specialized one. Real problems are multifaceted and demand multifaceted solutions. Engaging students in the study of the liberal arts can provide a basis for lifelong learning and civic involvement.
Calcium Bis[bis(trimethylsilyl)amino‐triethylgallate] — A Molecule with Ca‐C‐Ga Three‐Center Bonds
Authors: Westerhausen Matthias , Weinrich Sabine , Oßberger Manfred , Mitzel Norbert W. 
Published: June 2004

AbstractThe reaction of calcium‐bis[bis(trimethylsilyl)amide] with two equivalents triethylgallium yields nearly quantitatively the addition product. In the solid state the calcium atoms are coordinated by two nitrogen atoms and two ethyl groups, whereas in solution all ethyl substituents are magnetically equivalent even at low temperatures. The Ca‐C‐Ga two‐electron three‐center bonds show mean Ca‐N and Ca‐C distances of 243 and 268 pm, respectively.
A Hydrogen Adipato‐bridged Copper(II) Coordination Polymer: [Cu(bpy)(HL)]2L · 6H2O (bpy = 2, 2'‐Bipyridine, H2L = Adipic Acid)
Authors: Zheng Yue‐Qing , Lin Jian‐Li 
Published: June 2004

AbstractReaction of a fresh Cu(OH)2x(CO3)1—x · yH2O precipitate with adipic acid (H2L) and 2, 2'—bipyridine (bpy) in ethanolic aqueous solution at room temperature afforded the hydrogen adipato bridged CuII coordination polymer [Cu(bpy)(HL)]2L · 6H2O consisting of double chains according to {[Cu(bpy)(HL)2/2]2L} and hydrogen bonded H2O molecules. The chains result from [Cu(bpy)]2+ units bridged by bis—monodentate hydrogen adipato ligands and further crosslinked by bis—monodentate adipato ligands. Through the interchain π—π stacking interactions and interchain C(bpy)—H···O(adipato) hydrogen bonding interactions, the double chains are assembled into layers, between which the crystal H2O molecules are located. The Cu atoms are square pyramidally coordinated by two N atoms of one bpy ligand and three O atoms of one adipato ligand and two hydrogen adipato ligands. The doubly bonded oxygen atom of the protonated carboxyl group occupies the apical position (Cu—N: 1.997, 2.005 Å; equatorial Cu—O: 1.925, 1.942 Å; apical Cu—O: 2.354 Å). Furthermore, the thermal behavior of the compound will be discussed. Crystal data: triclinic, P1¯ (no. 2), a = 9.618(1) Å, b = 9.933(1) Å, c = 12.782(2) Å, α = 70.88(1)°, β = 73.70(1)°, γ = 75.60(1)°, V = 1090.7(2) Å3, Z = 1, R = 0.0453 and wR2 = 0.1265 for 4643 observed reflections (Fo2 > 2σ(Fo2)) out of 4985 unique reflections.
The Crystal Structure of Solvent‐Free Silver Dodecachloro‐closo‐dodecaborate Ag2[B12Cl12] from Aqueous Solution
Authors: Tiritiris Ioannis , Schleid Thomas 
Published: June 2004

AbstractColourless octahedral single crystals of solvent‐free Ag2[B12Cl12] (cubic, Pa3¯; a = 1238.32(7) pm, Z = 4) are obtained by the metathesis reaction of Cs2[B12Cl12] with an aqueous solution of silver nitrate (AgNO3) and recrystallization of the crude product from water. The crystal structure is best described as a distorted anti‐CaF2‐type arrangement in which the quasi‐icosahedral [B12Cl12]2— anions (d(B—B) = d(B—Cl) = 177—180 pm) are arranged in a cubic closest‐packed fashion. The tetrahedral interstices are filled with Ag+ cations which are strongly displaced from their ideal positions. Thereby each silver atom gets coordinated by six chlorine atoms from the edges of three [B12Cl12]2— anions providing a distorted octahedral coordination sphere to the Ag+ cations (d(Ag—Cl) = 283—285 pm, CN = 6).
Synthese, spektroskopische Charakterisierung und Molekülstrukturen ausgewählter Lewis‐Basen‐Addukte der Alkalimetall‐tri(tert‐butyl)silylphosphanide
Authors: Westerhausen Matthias , Weinrich Sabine , Schmid Bertram , Schneiderbauer Stefan , Suter Max , Nöth Heinrich , Piotrowski Holger 
Published: June 2004

AbstractDie Metallierung von Tri(tert‐butyl)silylphosphan mit Butyllithium und den Bis(trimethylsilyl)amiden von Natrium, Kalium und Rubidium ergibt quantitativ die entsprechenden Alkalimetall‐tri(tert‐butyl)silylphosphanide, die nach Zugabe geeigneter Lewis‐Basen als dimeres (DME)LiP(H)SitBu3 (1), kettenförmiges (DME)NaP(H)SitBu3 (2), monomeres ([18]Krone‐6)KP(H)SitBu3 (3) und dimeres (TMEDA)1.5RbP(H)SitBu3 (4) kristallin isoliert werden. Die Umsetzung von H2PSitBu3 mit Caesium‐bis(trimethylsilyl)amid bei Zimmertemperatur liefert zunächst ein monocyclisches tetrameres Caesium‐tri(tert‐butyl)silylphosphanid (5), an das noch zwei weitere CsN(SiMe3)2‐Moleküle koordinieren. Erst bei 80 °C reagiert dieser Komplex mit weiterem Phosphan zum tetrameren Toluol‐Addukt (η6‐Toluol)CsP(H)SitBu3 (6), dessen zentrales Strukturelement das Cs4P4‐Heterokubanfragment bildet. Die Zusammensetzung dieser Verbindungen konnte durch Einkristallstrukturuntersuchungen belegt werden.
Ln2(ClO4)2(H2I2O10) · 8H2O (Ln = Sm, Gd), a Lanthanide Perchlorate Mesodiperiodate forming a Novel Layer Structure
Authors: Fischer Andreas 
Published: June 2004

AbstractBy slow evaporation of solutions containing Ln(ClO4)3 (Ln = Sm, Gd), H5IO6 and an excess of HClO4, crystals of the title compounds could be obtained. Their structures were determined by single‐crystal X‐ray diffraction. The compounds crystallize in the monoclinic crystal system, space group P21/c. They contain Ln3+ ions, which are coordinated by [H2I2O10]4— anions forming two‐dimensional, cationic networks. These are separated by perchlorate ions, forming a layered structure.
Synthesis and Crystal Structure of Bis(methyltriethylammonium) Hexabromotellurate(IV)‐tris{dibromodiselenate(I)}, [NMeEt3]2n[TeBr6(Se2Br2)3]n, Containing a Chain‐Polymeric Mixed‐valence Bromotellurate(IV)‐Selenate(I) Anion
Authors: Janickis Vitalijus , Herberhold Max , Necas Marek , Milius Wolfgang 
Published: June 2004

AbstractRed crystals of [NMeEt3]2n[TeBr6(Se2Br2)3]n (1) were isolated when selenium and bromine (1:1) were allowed to react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriethylammonium bromide (1:2). The salt 1 crystallizes in the monoclinic space group C2/c with the cell dimensions a = 27.676(6) Å, b = 9.665(2) Å, c = 18.796(4) Å and ß = 124.96(3)° (120 K). The [TeBr6(Se2Br2)3]2— anions contain nearly regular octahedral [TeBr6]2— ions which are incorporated into a polymeric chain by bonding contacts between 3 facial bromo ligands and 3 Se2Br2 molecules, one of which is situated on the twofold symmetry axis. The distances between the μBr ligands and the SeI atoms of the Se2Br2 molecules are observed in the range 3.308(2) — 3.408(2) Å and can tentatively be interpreted as donor‐acceptor bonds with μBr as donors and Se2Br2 as acceptors. The TeIV—Br distances are in the range 2.669(1) — 2.687(1) Å. The bond lengths in the connecting Se2Br2 molecules are: SeI—SeI = 2.267(2) and 2.281(2) Å, SeI—Br = 2.340(1), 2.353(1) and 2.337(1) Å.
Alkali Metal Compounds of Hydroquinone: Synthesis and Crystal Structure
Authors: Couhorn U. , Dronskowski R. 
Published: June 2004

AbstractA number of novel routes to the alkali metal compounds of hydroquinone M2[p‐C6H4O2] (M = Li, Na, K, Rb, Cs) and M[p‐C6H4O(OH)] (M = K, Rb, Cs) have been synthetically explored. The selective synthesis of the alkali 4‐hydroxyphenolates and 1, 4‐phenylenediolates is based on optimized reaction conditions (solvents, temperatures).All compounds were structurally characterized by means of powder X‐ray diffraction using Rietveld profile refinement including C—C and C—O bond distance restraints. The atomic arrangement of M2[p‐C6H4O2](M = Na, K) (tetragonal, space group: P42/ncm) is characterized by infinite pillars of [M2[3]O2[3]]‐units along the c axis connected by [p‐C6H4O2]2—‐anions with stacking direction along c. The coordinatively unsaturated alkali metals, surrounded by three oxygen atoms, exhibit symmetrical (K) as well as asymmetrical (Na) interactions with the phenylene rings. M[p‐C6H4O(OH] (M = K, Rb) (tetragonal, space group: P4/n) forms hydrogen‐bridged linear chains of [p‐C6H4O(OH)]—‐anions along the c direction. The phenylene planes of neighboring chains have an almost orthogonal arrangement while the interchain planes are parallel. K and Rb are fourfold coordinated by two different oxygen coordination spheres.