bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Mineral Building Materials by Mercury‐Intrusion Porosimetry
Authors: Rübner Katrin , Hoffmann Dirk 
Published: June 2006

AbstractMineral building materials are generally heterogeneous and porous solids. Their engineering properties are closely associated with their porosity and pore‐size distribution, which can be studied by mercury intrusion. The entire pore‐size distribution curves are used to determine changes in the pore structure of a material class in a qualitative way. Certain parameters derived from pore‐size distributions can be correlated to engineering properties. These key values are applied as criteria to evaluate the quality and durability of a building material. However, because of the heterogeneity of natural and artificial building materials and the influence of moisture content on their pore structure the results are strongly affected by preparation conditions such as sampling and drying. A correct analysis requires a knowledge of these effects. The paper describes the use of mercury porosimetry to study mineral building materials such as cementitious materials, bricks, and renderings. Furthermore, the influence of preparation effects on the precision of measurements is discussed.
Domain Complexion Diagrams Related to Mercury Intrusion‐Extrusion in Monte Carlo‐Simulated Porous Networks
Authors: Felipe Carlos , Cordero Salomón , Kornhauser Isaac , Zgrablich Giorgio , López Raul , Rojas Fernando 
Published: June 2006

AbstractPorous networks of sites (cavities) and bonds (throats) are simulated by a Monte Carlo procedure; the connectivity (C) being the mean number of bonds surrounding a site. For simulating Hg intrusion‐extrusion processes, canthotaxis at site‐bond joints and snap‐off of Hg threads are considered. Hg porosimetry is illustrated in terms of domain complexion diagrams (DCD), these being graphs that depict the sites and bonds of given sizes that are either Hg‐filled or not. DCD plots show that during Hg intrusion: (i) the capillary resistance to Hg access becomes smaller as C increases, the bond sizes get larger, and canthotaxis is absent; (ii) in highly pore size correlated networks, the Hg filling sequence of sites occurs from the larger to the smaller voids; (iii) in lowly pore size correlated networks, Hg intrusion occurs homogeneously with respect to the whole set of site sizes. During extrusion, Hg entrapment is more intense when: (i) C is low, (ii) the pore size correlation is small, and (iii) the snap‐off phenomenon is extensive. Hg extrusion DCD plots show that for high C: (i) Hg is trapped inside the largest sites if the pore size correlation is null or medium; and (ii) at higher pore size correlations, Hg is retained over a wide range of site sizes. For networks of low C, Hg is trapped over a wide variety of cavity sizes irrespective of the pore size correlation.
Liquid Expulsion Permporometry – a Tool for Obtaining the Distribution of Flow‐Through Pores
Authors: Šolcová Olga , Hejtmánek Vladimír , Šnajdaufová Hana , Schneider Petr 
Published: June 2006

AbstractThe permporometry technique, common in the fields of thin filters, membranes etc., was extended to porous solids with far larger thicknesses. The basic idea of permporometry is the controlled expulsion of a suitable liquid from pores of different sizes by increasing the gas pressure difference across the tested porous solid. The gas flow rate through liquid‐free pores then corresponds to the amount of pores with different sizes. Two modes of measurement were suggested and tested. The contribution of the Knudsen flow mechanism was taken into account in addition to the usually anticipated viscous gas flow mechanism.It was confirmed that both measurement modes give consistent pore size distributions (PSD) of flow‐through pores. Permporometry PSDs were compared with results from mercury porosimetry and pseudo‐steady state permeation. It appears that permporometry should be considered as a standard textural characterization technique suitable for the prediction and simulation of gas flow through porous media in all processes where gas transport takes place.
The Physical Significance of Mercury Porosity Hysteresis in the Characterization of Calcined Precipitated Alumina
Authors: Carruthers J. Donald 
Published: June 2006

AbstractActivated alumina, for application as a catalyst support or as an adsorbent, is often obtained industrially via calcination of precipitated aluminum oxide hydrate. Its preparation conditions depend on the ultimate application, which, in turn, dictates its target specifications, e.g., surface area (SA), total pore volume (PV), pore size distribution (PSD) and density. Invariably, some method of porosity characterization is required periodically during manufacture for process control and at the final stage of alumina certification. Although gas and vapor adsorption methods were common in the early days of alumina production, mercury porosimetry (MP) has become the technique of choice in the past 30 years. MP provides valuable information about the meso‐ and macro‐pore structure of the alumina but the hysteresis, seen in each analysis, has been difficult to interpret. In this work the MP porosity of a wide variety of calcined aluminas is contrasted with thermogravimetric (TGA) analyses of the source aluminum oxide hydrates and the precipitation and activation conditions, which generated the aluminas in an attempt to better understand the hysteresis phenomenon. The results imply a “connectivity”, or internal structure, explanation for MP hysteresis in calcined aluminas.
Defining the fold space of membrane proteins: The CAMPS database
Authors: Martin‐Galiano Antonio J. , Frishman Dmitrij 
Published: June 2006

AbstractRecent progress in structure determination techniques has led to a significant growth in the number of known membrane protein structures, and the first structural genomics projects focusing on membrane proteins have been initiated, warranting an investigation of appropriate bioinformatics strategies for optimal structural target selection for these molecules. What determines a membrane protein fold? How many membrane structures need to be solved to provide sufficient structural coverage of the membrane protein sequence space? We present the CAMPS database (Computational Analysis of the Membrane Protein Space) containing almost 45,000 proteins with three or more predicted transmembrane helices (TMH) from 120 bacterial species. This large set of membrane proteins was subjected to single‐linkage clustering using only sequence alignments covering at least 40% of the TMH present in a given family. This process yielded 266 sequence clusters with at least 15 members, roughly corresponding to membrane structural folds, sufficiently structurally homogeneous in terms of the variation of TMH number between individual sequences. These clusters were further subdivided into functionally homogeneous subclusters according to the COG (Clusters of Orthologous Groups) system as well as more stringently defined families sharing at least 30% identity. The CAMPS sequence clusters are thus designed to reflect three main levels of interest for structural genomics: fold, function, and modeling distance. We present a library of Hidden Markov Models (HMM) derived from sequence alignments of TMH at these three levels of sequence similarity. Given that 24 out of 266 clusters corresponding to membrane folds already have associated known structures, we estimate that 242 additional new structures, one for each remaining cluster, would provide structural coverage at the fold level of roughly 70% of prokaryotic membrane proteins belonging to the currently most populated families. Proteins 2006. © 2006 Wiley‐Liss, Inc.
One‐electron approach to describe charge and orbital order in Mn2OBO3
Authors: Matos M. , Oliveira R. B. 
Published: June 2006

AbstractA detailed study is performed on the band structure of the mixed‐valent Mn2OBO3 warwickite, by using the high‐spin filling (hsf) scheme in the extended Hückel approach. It is found that charge ordering, found experimentally to be adopted by the compound, is associated with orbital order, represented by the presence of x2 − y2 holes in Mn1. The hsf scheme provides considerable improvement in the calculation of charge distribution in the material, as compared with the usual band filling scheme, with both Mn1 and Mn2 cations exhibiting positive charge. In addition, the octahedral distortion around Mn1 is correctly described as a Jahn–Teller (JT) type‐distortion. The calculated electronic band structure provides evidence that the Mn warwickite is an insulator, in agreement with experimental data. O1, connected to the JT‐like distortion of Mn1, is found to be loosely bound to the structure, as compared with other O‐atoms in the lattice, showing a favorable condition in the structural stability of the compound. Comparison is made with the mixed‐valent Fe2OBO3 warwickite. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Quark–boson molecular orbital calculations
Authors: Pavão Antonio C. , Ferreira Joacy V. 
Published: June 2006

AbstractAb initio molecular orbital calculations are performed on the system composed of a static three u(+2/3) quark core coupled to a b− boson cloud. Using appropriated Gaussian basis set functions to describe interactions at Fermi distances, this quark–boson system can be used as a proton model. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Application of the equivalent‐core calculation to the Cl in core level on condensed SiCl4
Authors: Mota G. V. S. , Costa F. L. P. 
Published: June 2006

AbstractUtilization of the equivalent core may be of great help in the determination of excitation energies for condensed systems. This method presents a small difference in the excitation potential in relation to the experimental values, thus, enabling a better symmetry assignment for the excitations involved in the process. With the help of (Z+1)‐core model, we estimated the absorption position and the symmetry for the discrete core‐excitation state of the Cl K edge on SiCl4 and were able to understand the process of selective fragmentation for condensed systems with good calculation approximation. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Theoretical study of cooperative effects in the homo‐ and heteromeric hydrogen bond chains (HCN)nHF withn= 1, 2, and 3
Authors: Araújo Regiane C. M. U. , Soares Verneck M. , Oliveira Boaz G. , Lopes Kelson C. , Ventura Elizete , Do Monte Silmar A. , Santana Otávio L. , Carvalho Antônio B. , Ramos Mozart N. 
Published: June 2006

AbstractTheoretical investigations concerning the formation of hydrogen bonds in both homomeric, (HCN)n, and heteromeric clusters of the type (HCN)nHF (n= 1, 2, and 3) have been performed through ab initio molecular orbital calculations at the second‐order Møller–Plesset (MP2) and density functional theory (DFT)/B3LYP levels, with the 6‐311++G(d,p) basis set. The formation of hydrogen bonds is investigated in terms of changes in structural, electronic, and vibrational parameters of the free species. Important parameters include the increment in the distance of the HF proton donor species, the increment in the HC distance of HCN moiety, and the amount of intermolecular charge transfer between the HCN species in the (HCN)ngroup. It is interesting to point out the different behavior in the HC distance as HCN acts simultaneously as a proton acceptor, proton donor, and a proton donor and acceptor. Other important results concern the cooperative effect (CE) in terms of the stabilization energy and dipole moment. Both CEs increase with cluster size and are more pronounced for the heteroclusters. The HF stretching frequency is red‐shifted on going in the direction (HCN)HF → (HCN)2HF → (HCN)3HF. This trend is in agreement with the following order of stabilization energies: ΔEHCN…HF< ΔE< ΔE. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Increasing retention and success of students of color at research‐extensive universities
Authors: Aragon Steven R. , Rios Perez Mario 
Published: June 2006

AbstractThe number of students of color transferring to and completing degrees at four‐year, non‐research‐extensive universities continues to increase. However, research‐extensive universities struggle with recruiting and retaining students of color. This chapter discusses one initiative developed by a research‐extensive university focused on increasing success and graduation rates of students of color.
Thermal and Structural Studies of a 1D Zinc(II) Coordination Polymer – [Zn(μ‐4,4′‐bipy)(H2O)4]n(CCl3COO)2n·(4,4′‐bipy)2n (4,4′‐bipy = 4,4′‐bipyridine), with Shorted Cl···Cl Interactions
Authors: Amiri Maryam Ghoreishi , Morsali Ali 
Published: June 2006

AbstractA 1D ZnII(μ‐4,4′‐bipy) coordination polymer with trichloroacetate anions, [Zn(4,4′‐bipy)(H2O)4]n(CCl3COO)2n·(4,4′‐bipy)2n, has been synthesized, characterized and studied by thermal and X‐ray crystallography. The structural studies show the Zn atoms have a distorted octahedral environment. Self‐assembly of this compound in the solid state is likely caused by hydrogen boding, shorted Cl···Cl and π‐π stacking interactions.
The Binding Properties of Terminal and Bridging Fluoride and of Aqua Ligands – a Semiempirical Vibronic Coupling and DFT Study of Mixed‐Ligand Manganese(III) Complexes
Authors: Reinen Dirk , Atanasov Mihail , Massa Werner 
Published: June 2006

AbstractA combined vibronic coupling and angular overlap analysis of MIIIL6 complexes, supplemented by basic DFT calculations, is performed where the 3d cations are CrIII, FeIII or the Jahn‐Teller unstable MnIII cation, and the ligands L fluoride – in terminal (Ft) or in bridging (Fb) function – or OH2. Our approach is mostly semiempirical and based on a novel ligand strain model, which utilises available structural and spectroscopic data and mostly deals with mixed‐ligand MnIII complexes, containing simultaneously Ft, Fb and H2O. Surveying the great number of published structural data, some interesting results concerning the differing binding properties are derived. While the total bond covalency is similar for the three ligands, the total bond strength – and hence also the ionic bond increment – follows the sequence: Ft ≫ OH2 > Fb. Partitioning the bond covalency into a part, which measures the ligand‐to‐metal charge flow (a), and an increment stemming from orbital (predominantly σ‐) overlap (b), one obtains: Ft ≫ Fb > OH2 for (a) and the reverse sequence for (b).DFT model calculations on the [MIII(Ft)6]3− polyhedra in a solvent continuum were the basis for the elucidation of reliable ground state potential energy surfaces also for the further investigated complexes. The sometimes only very small energy difference between the involved three minima, generated via the interaction with the Jahn‐Teller active vibrational ϵg mode, led to various orthorhombic distortion conformers in the range between the tetragonal elongation and compression, depending on the strain magnitude imposed on the [Mn(Ft)6]3− parent polyhedron by a Ft‐by‐Fb (or OH2) substitution. It is further remarkable, that the average bond length of the Jahn‐Teller distorted octahedron varies significantly with the extent of the deformation and wether it is elongated or compressed – providing also computational evidence for the experimentally observed additional coupling to the totally symmetric α1g mode (Eg ⊗(ϵg + α1) vibronic interaction). The Jahn‐Teller stabilisation energy of the D4h‐elongated [MnIII(Ft)6]3− complex (absolute minimum) with respect to the regular octahedron can be defined as the difference between the non‐Jahn‐Teller restoring energy(≈ 0.3 eV) and the vibronic energy (≈ 0.65 eV). It is considerable (≈ −0.35 eV) in comparison to the stabilisation in regard to the compressed D4h‐conformer (≅ −0.075 eV).DFT was not successful in calculating d‐d transition energies within the 5Eg ground state of MnIII complexes containing the aqua ligand. Apparently, hydrogen bonds of varying strength to the higher‐sphere chemical environment and with significant energetic retroaction on the MnIII‐OH2 bonds exist, which cannot be correctly simulated by non‐sophisticated DFT.
Synthesis, Spectral Properties and Crystal Structure of Calcium and Strontium Complexes of 1,10‐Phenanthroline
Authors: Neykov Mihail , van Almsick Tobias , Dimitrov Georgi 
Published: June 2006

AbstractThree new complexes of 1,10‐Phenanthroline (phen), [Ca(phen)2(H2O)2(NO3)](NO3) (1), [Sr(phen)2(H2O)2(NO3)](NO3) (2) and [Ca(phen)2(H2O)2(NO3)][BF4] (3) were synthesized and characterized by UV, FT IR, Raman, and MS spectra. Their crystal structures were also determined. In 1 and 2 only one of the (NO3)− is coordinated to the central atom. The other (NO3)− is away from the metal ion and was replaced by [BF4]− under the conditions of a competitive reaction. The two phenanthroline molecules also occupy nonequivalent positions showing typical π – π interactions in their crystal packing.
The First Cadmium(II) Complex based on the 4‐Aminocinnamato Ligand with unusual 4.82 Topology
Authors: Zhang Qi‐Wei , Wen Yi‐Hang , Feng Yun‐Long 
Published: June 2006

AbstractThe first CdII complex based on the 4‐aminocinnamato ligand, [Cd3Cl2(OH)2(AC)2(H2O)2]n (1), (AC = 4‐aminocinnamato), has been synthesized by hydrothermal reaction and structurally determined. Complex 1 crystallizes in the monoclinic space group P21/c with cell parameters: a = 14.2599(10), b = 6.6329(5), c = 12.5568(10) Å, β = 95.069(4))°, V = 1183.03(15) Å3, Z = 2. Complex 1 consists of [Cd3Cl2(OH)2]n chains doubly bridged by AC ligands, forming a 2‐D network with unusual 4.82 topology. Hydrogen bonds between the layers result in the final 3D frameworks.
Synthesis and Structural Characterization of the Ammelinium Salts [C3H6N5O]Cl, [C3H6N5O]Br, and [C3H6N5O]NO3
Authors: Lotsch Bettina V. , Schnick Wolfgang 
Published: June 2006

AbstractThe salts ammelinium chloride [C3H6N5O]Cl, ammelinium bromide [C3H6N5O]Br, and ammelinium nitrate [C3H6N5O]NO3 were obtained by hydrolysis of melam hydrate with the respective concentrated mineral acids. The structures of the molecular salts were elucidated by single–crystal X–ray diffraction and vibrational spectroscopy, thus representing the first examples of structurally characterized ammeline derivatives. All ammeline salts crystallize in the monoclinic space group P21/c with 4 formula units in the unit cell. The hydrochloride (a = 5.354(2), b = 14.673(3), c = 8.152(2) Å, β = 90.00(3)°, V = 640.4(2) Å3, T = 293 K), hydrobromide (a = 5.212(1), b = 8.831(2), c = 14.577(3) Å, β = 98.97(3)°, V = 662.7(2) Å3, T = 130 K), and nitrate salt (a = 9.332(2), b = 6.256(2), c = 13.511(3) Å, β = 108.05(3)°, V = 750.0(3) Å3, T = 130 K) all contain planar, mono–protonated ammelinium cations which are hydrogeñbonded to the respective halide or nitrate anions. The noñisotypic structures are composed of anion – cation arrays forming either planar (chloride) or corrugated (nitrate) layers, or strands with differing stacking sense (bromide), respectively. Notably, the keto tautomer with C2v symmetry is representing the actual proton distribution rather than the hydroxy tautomer, which based on ab initio calculations has recently been predicted to be the more stable one for the parent base ammeline.
The First Complex of Diallylpolysulfide: Synthesis and Crystal Structure of [Cu3Br3(CH2=CH‐CH2‐(S)4‐CH2‐CH=CH2)]
Authors: Salivon N. F. , Filinchuk Y. E. , Olijnyk V. V. 
Published: June 2006

AbstractA crystalline π‐complex [Cu3Br3(CH2=CH‐CH2‐(S)4‐CH2‐CH=CH2)] has been obtained by an alternating‐current electrochemical synthesis starting from CuBr2 and diallyltetrasulfide (DATS). Its structure is orthorhombic, space group Pbca, a = 9.9911(6), b = 23.2792(16), c = 12.8005(9) Å, V = 2977.2(3) Å3 (at 293 K), Z = 8; R1 = 0.0377, wR2 = 0.0760. The DATS molecule behaves as a bichelate pentadentate ligand: Cu1 atom is chelated by one of the two olefin groups and a weakly bonded sulfur atom, Cu3 atoms is chelated by two sulfur atoms and Cu2 is coordinated to the second olefin group. Centrosymmetric and pseudo‐centrosymmetric Cu2Br2 units are associated into a finite Cu6Br6 fragment by Cu…Br contacts of 3.116(1) Å.
Synthesis and Crystal Structure of Cobalt(II) and Cadmium(II) Complexes with the Flexible Tripodal Ligand 1,3,5‐Tris(4‐pyridylmethoxyl)benzene
Authors: Wu Gang , Zhang Zheng‐Hua , Okamura Taka‐aki , Sun Wei‐Yin , Ueyama Norikazu 
Published: June 2006

AbstractThree complexes [Co(L4)(DMF)(H2O)(NO3)]NO3· DMF·0.5H2O (1), [Co(L4)2(SCN)2]·4CH3OH·H2O (2) and [Cd(L4)(bipy)(H2O)2](ClO4)2·4H2O (3) (DMF = N, N‐dimethylformamide, bipy = 4,4′‐bipyridine) were synthesized by reactions of ligand 1,3,5‐tris(4‐pyridylmethoxyl)benzene (L4) with the corresponding metal salts and their structures were determined by X‐ray single‐crystal structure analysis. Complex 1 crystallizes in monoclinic space group C2/c with cell parameters a = 26.200(9) Å, b = 17.465(5) Å, c = 17.275(5) Å, β = 118.183(10)°, V = 6968(4) Å3, Z = 8, while complexes 2 and 3 crystallize in triclinic space group $P{\bar 1}$ with different cell parameters, complex 2: a = 9.3077(7) Å, b = 14.7251(7) Å, c = 21.4745(13) Å, α = 70.380(4)°, β = 83.161(4)°, γ = 82.350(4)°, V = 2738.9(3) Å3, Z = 2; complex 3: a = 9.797(6) Å, b = 11.807(6) Å, c = 13.970(11) Å, α = 88.03(6)°, β = 88.77(6)°, γ = 74.53(5)°, V = 1556.4(17) Å3, Z = 1. In complexes 1, 2 and 3, all the metal atoms adopt distorted octahedral coordination, however, the ligand L4 have different coordination modes. In complex 1, the ligand acts as a three‐connected node to coordinate with three CoII atoms, and generate a doubly interpenetrated (10, 3)‐b three‐dimensional framework. In complex 2, each ligand L4 uses two of three arms to link two CoII atoms to form an infinite one‐dimensional hinged chain structure, while in complex 3, the L4 only serves as a terminal monodentate ligand.
Synthesis, Structure and Spectral Properties of [Ni(TAMEN)](ClO4)2·DMF (TAMEN = N,N′‐Tetra(4‐antipyryl‐methyl)‐1,2‐diaminoethane), a Mannich Base Complex of Biological Relevance
Authors: Tudose Ramona , Mosoarca Elena‐Maria , Pantenburg Ingo , Costişor Otilia , Meyer Gerd 
Published: June 2006

AbstractThe new mononuclear complex [Ni(TAMEN)](ClO4)2·DMF (TAMEN = N,N′‐tetra‐(4‐antipyrylmethyl)‐1,2‐diaminoethane) has been synthesized and its crystal structure was determined by single‐crystal X‐ray diffraction. It crystallizes with monoclinic symmetry, space group P21/c (no. 14) and unit cell parameters of a = 10.8736(3), b = 10.9560(4), c = 45.820(2) Å, β = 90.23(1)°, Z = 4. The TAMEN molecule acts as a hexadentate ligand incorporating a 1,2‐diaminoethane bridge in the staggered conformational gauche isomer. The nickel(II) ion is octahedrally coordinated with metal‐ligand distances ranging from 2.023(2) to 2.145(3) Å. Electronic and vibrational spectroscopy data agree well with the crystal structure.
Monoalkylaluminium Complexes Stabilized by a Rigid Dianionic Diimine Ligand: Synthesis, Solid State Structure, and Dynamic Solution Behaviour of (dpp‐BIAN)AlR (R = Me, Et, iBu)
Authors: Lukoyanov Anton N. , Fedushkin Igor L. , Schumann Herbert , Hummert Markus 
Published: June 2006

Abstract(dpp‐BIAN)Na2 (dpp‐BIAN = 1,2‐bis[(2,6‐di‐iso‐propylphenyl)imino]acenaphthene) reacts with two equivalents of R2AlCl in Et2O to give the monoalkylaluminium complexes (dpp‐BIAN)AlR(Et2O) (R = Me, 1; Et, 2; iBu, 3). Compounds 1‐3 have been characterized by elemental analysis, IR and 1H NMR spectroscopy. Single crystal X‐ray diffraction has been used to determine the molecular structures of 1 and 2. Both structures show the aluminium atom tetrahedrally coordinated by the two N atoms of the dianionic dpp‐BIAN ligand, the alkyl group, and a diethyl ether molecule. Temperature dependent 1H NMR spectroscopic measurements of 2 in THF‐d8 revealed a dynamic process caused by positional exchange between the ethyl group and the ether molecule relative to the metallacycle, which slows down with decreasing temperature. In the case of the methyl derivative 1, the corresponding process is fast at ambient as well as at low temperatures, whereas in the case of the isobutyl derivative 3 the larger size of the alkyl group prevents such a positional ligand exchange already at room temperature.