bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthetic and Structural Studies of 1‐Sila‐2,5‐diaryltetrazenes
Authors: Frenzel Andrea , Buffy Jarrod J. , Powell Douglas R. , West Robert , Müller Thomas 
Published: July 2007

AbstractThe reaction between aryl azides and lithiated aryl amines leads to tetrazenes 3 and 9 which contain a chain of four nitrogen atoms. Reaction with different halosilanes gives the cyclic silatetrazenes 10, 12, and 15 where substitutents on the silicon vary form alkyl to hydrogen and chlorine atoms. The structures of 10, 12, and 15 in the solid state are reported. Variation of the solvent and the Lewis acidity of the halosilane influence the ratio of silatetrazene to side products, bissilyated amines. These effects are studied for different halosilanes.
Synthesis and Structure of Trimethyllead Niobocene Dihydride
Authors: Nikonov Georgii, I. , Avtomonov Evgeni V. , Massa Werner 
Published: July 2007

AbstractThe reaction of niobocene trihydride [Cp2NbH3] with ClPbMe3 in the presence of amine affords the plumbido dihydride complex [Cp2NbH2(PbMe3)] (1). Compound 1 represents the first example of a stable complex with neighbouring hydride and terminal plumbyl substituents. The structure of this compound has been established by NMR and IR spectroscopy and confirmed by an X‐ray structure analysis.
Steric Effects on Base Adduct Formation and Crystal Structures of Diastereomers of a Nickel(II) Schiff Base Complex
Authors: Jäger Ernst‐G. , Schuhmann Kerstin , Görls Helmar 
Published: July 2007

AbstractReaction of the ligand meso‐H2L, derived from cis‐diaminocyclohexane and ethyl cyano(ethoxymethylene)acetate, with nickel(II) acetate gives meso‐NiL. Spectrophotometric titration of RR‐NiL and meso‐NiL with various nitrogen bases reveals a strong influence of the steric hindrance of the diaminocyclohexanediyl bridge in meso‐NiL on the base adduct stability. The structures of RR‐NiL and meso‐NIL have been established by X‐ray diffraction.
Contribution to the Chemistry of Boron, 240 . Studies on Benzo‐1,3,2‐diphosphaborolanes, Benzo‐1,4,2,3‐diphosphadiborinanes and Benzo‐1,5,2,3,4‐diphosphatriborepanes
Authors: Kaufmann Bernhard , Jetzfellner Ralf , Nöth Heinrich , Schmidt Martin , Leissring Elke , Issleib Kurt 
Published: July 2007

AbstractA series of benzo‐ 1,3,3‐diphosphaborolanes C6H4(PR)2BR' (R = H, iPr, SiMe3; R' = R2N, R) has been prepared by several routes and characterized by spectroscopic and – in part – by X‐ray diffraction methods. They feature pyramidal P atoms with the substituents in antiperiplanar positions. The P atoms act as coordination sites for the (CO)5Cr fragment. In contrast to the R2N‐bearing benzo‐1,3,2‐diphosphaborolanes, the derivative C6H4(PH)2BCMe3 (4f) dimerizes by additional B–P bond formation to produce a pentacyclic system (4f)2. – The reaction of C6H4(PHNa)2 with B2(NMe2)2Cl2 in THF/hexane yields the acyclic phosphanylborane Me2NB(PH–C6H4PH2)2 (15). However, if C6H4[P(iPr)Li]2 is allowed to react with B2(NMe2)2Cl2, the benzo‐1,4,2,3‐diphosphadiborinane 13 is obtained, together with its rearrangement product 2‐bis(dimethylamino)borylbenzo‐1,3,2‐diphosphaborolane 14 which dimerizes to (14)2. — In contrast, the almost planar ring of the 2,3‐dimesitylbenzo‐1,4,2,3‐diphosphadiborinane (16) possesses P and B atoms with a planar geometry. Short B–B and B–P bonds suggest that this new heterocycle can be regarded as a 6π electron system. Moreover, the benzo‐1,5,2,3,4‐diphosphatriborepane 18 forms readily forms readily from C6H4(PHNa)2 and Br(Me2N)B–B(N‐Me2)–B(NMe2) Br to give a tub‐shaped seven‐membered C2B3P2 ring system with the P atoms in a pyramidal and the B atoms in a planar environment.
Geminal di(hypersilyl) Compounds — the Synthesis and Structure of Bis[tris(trimethylsilyl)silyl]methanol
Authors: Gross Thoralf , Oehme Hartmut , Kempe Rhett 
Published: July 2007

AbstractTris(trimethylsilyl)silyllithium (1) reacts with methyl formate in diethyl ether (molar ratio 2:1) to give 1,2‐di(hypersilyl)‐ ethylene 13. The formation of 13 proceeds through the intermediates formyl tris(trimethylsilyl)silane (4) and lithium bis‐[tris(trimethylsilyl)silyl]methoxide (5). In diethyl ether, the alkoxide 5 spontaneously eliminates lithium trimethylsilanolate thereby generating 1,1‐bis(trimethylsilyl)−2‐[tris(trimethylsilyl)silyl]silene (9), which undergoes a formal [2+2] cycloaddition with the carbonyl compound 4 to afford 13. This was verified by crossover experiments. In Pentane, the alkoxide 5 is moderately stable. Thus, the intermediate 5, prepared by reaction fo 1 with tert‐butyl formate in pentane. was protonated with water to give the di(hypersilyl)methanol 6 in good yield. The structure of 6 in good yield. The structure of 6 was elucidated by an X‐ray crystal structure analysis, which expectedly revealed tremendous distortions of the molecular skeleton. Thus, the spatial demand of the two extended hemispherical (Me3Si)3Si groups forces a widening of the Si–C–Si angle at the central sp3 carbon atom to a value of 135.5°.
A Monomeric Bis(arena)lead(II) Complex with a Plumbocene‐like Bent Sandwich Structural Unit — Structure of [Pb(1,2‐C6H4Me2)2(AlCl4)2
Authors: Frank Walter , Wittmer Franz‐Georg 
Published: July 2007

AbstractBis(o‐xylene)lead(II) bis(tetrachloroaluminate), obtained from lead(II) chloride and aluminium trichloride in o‐xylene, has been shown by X‐ray crystallography to be a mononuclear lead complex with point group symmetry C2 The two aromatic ligands are arranged similarly to those in monomeric plumbocene. The coordination sphere is completed by two bidentate AlCl4−ions. The lead center uses about a quarter of its bonding capability for each of the four ligands
Titanium and Zirconium Complexes Containing a Novel Dianionic Trifunctional Amido Ligand
Authors: Friedrich Stefan , Schubart Martin , Gade Lutz H. , Scowen Ian J. , Edwards Andrew J. , McPartlin Mary 
Published: July 2007

AbstractThe novel tridentate diamidoamine ligands [RC(2C5H4N)(CH2NSiMe3)2)2− (R = H, CH3) have been synthesized and coordinated to TiIV giving the pentacoordinate complexes [MX2(RC(2‐C5H4N)(CH2NSiMe3)2}] (M = Ti, Zr; X = Cl, Br). The crystal structure analysis of [TiBr2{HC(2‐C5H4N)(CH2)2}] (M = Ti, Zr; X = Cl, Br). The crystal structure analysis of [TiBr2{HC(2‐C5H4N)(CH2NSiMe3))] (10b) confirmed the involvement of the pyridyl function in the coordination to the meta centre occupying an apical position in the trigonal bipyramidal ligand polyhedron. alkylation of [TiCl2{H3CC(2‐C5H4N)(CH2NSiMe3)2)] (12a) with one or two molar equivalents of [RMgCl](R = PhCH2, Me3SiC2) yielded the mono‐ and dialkyl complexes [TiClR{H3CC(2‐C5H4N)(CH2NSiMe3)2)] and [TiR2(H3CC(2‐C5H4N)(CH2NSiMe3)2)] and [TiR2(H3CC(2‐C5H4N)(CH2NSiMe3)2}] in good yields. Depending on the steric demand of the alkyl group coordination or decoordination of the pyridyl group leads to four‐ or five‐coordinate species. A crystal structure analysis of the pentacoordinate complex [TiCl(CH2SiMe3){H3CC(2‐C5H4N)(CH2NSiMe3)2}] (16) was carried out.
Phosphanyl‐Substituted Phosphaferrocenes as p,p‐Chelate Ligands
Authors: Ganter Christian , Brassat Lutz , Ganter Beate 
Published: July 2007

AbstractDicyclohexyl‐acid diphenylphosphanyl‐substituted phosphaferrocenes 2 and 3 were synthesized by substitution of the amino group in 2‐dimethylaminomethyl‐3,4,‐dimethylphosphaferrocene 1 · Homologization of 2‐formyl‐3,4‐dimethylphosphaferrocene 4 by one CH2 unit via Wittig olefination provided access to the phosphanylethyl derivative 9. Ligands 2, 3 and 9 formed P, P‐chelate complexes with tetracarbonyl metal fragments in good yield. X‐ray crystal structure determinations were carried out for the five‐ring chelate complex 2. Mo(CO)4 (≡ l0), and the six‐ring chelate complex 9 . Mo(CO)4, (≡ 13).
Cyclic Diynes with Silicon in the Bridges: Structural and Photoelectron Spectroscopic Investigations
Authors: Stahr Helmut , Gleiter Rolf , Haberhauer Gebhard , Irngartinger Hermann , Oeser Thomas 
Published: July 2007

AbstractThe structures of 6‐isopropylidene‐1,1‐dimethyl‐1‐silacyclodeca‐3,8‐diyne (2), 1,6‐dimethyl‐1,6‐disilabicyclo[4.4.4]tetradeca‐3,8,12‐tryine (4), and 1,1,2,2,3,3‐hexamethyl‐1,2,3‐trisilacyclodeca‐4,9‐diyne (6) have been investigated by means of X‐ray crystallography. In 2 and 6 a chair conformation is adopted in the solid solid state. In 4 the three butyne groups are twisted around the SiSi axis against one another. The torsion along the triple bond axis (Si‐CH2‐CH2,/Si) amounts to 29.0(1). The He(I) photoelectron (PE) spectra of 2 and 6 together with those of 1,1‐dimethyl‐1‐silacyclodeca‐3,8‐diyne (1), 1,1,6,6‐tetramethyl‐1,6‐disilacyclodeca‐3,8‐diyne (3),1,12,2,3,3‐hexamethyl‐1,2,3‐trisilacycloundeca‐4,10‐diyne (7) have also been recorded. The PE spectra were interpreted on the basis of results from SCF MO calculations (3–21G*). They reveal a smaller splitting of the π‐bands in 1–3 as compared to cyclodeca‐1,6‐diyne. In the PE spectra of 5–7 we encountered a strong interaction between the silicon chain and the in‐plane π‐orbitals.
Dynamic Modeling and Simulation of Steam Cracking Furnaces
Authors: Ghashghaee M. , Karimzadeh R. 
Published: July 2007

AbstractThe transient modeling of thermal cracking furnaces is developed. This representation is capable of describing and predicting the unsteady‐state behavior of cracking furnaces during start‐up. To accurately predict the heat transfer to the reactor tube, the fireside conditions are coupled with the process side. The mutual interaction of these two sections is found to be very stiff in terms of convergence of the computations. The two‐dimensional transient zone model is developed for the radiative heat exchange calculation. A simplified model for the convection section is also used to predict the crossover temperature at each time increment. The main simulation outputs are the flue gas properties as well as the distributions of heat flux, refractory wall and coil skin temperatures versus time. The dynamic simulation is implemented for a conventional procedure used in the start‐up run of the olefin furnaces.
An Analysis of Pressure Drop and Holdup for Liquid‐Liquid Upflow through Vertical Pipes
Authors: Jana A. K. , Ghoshal P. , Das G. , Das P. K. 
Published: July 2007

AbstractThe present study has attempted to investigate pressure drop and holdup during simultaneous flow of two liquids through a vertical pipe. The liquids selected were kerosene and water. The measurements were made for phase velocities varying from 0.05–1.2 m/s for both liquids. The pressure drop was measured with a differential pressure transducer while the quick closing valve (QCV) technique was adopted for the measurement of liquid holdup. The measured holdup and pressure drop were analyzed with suitable theoretical models according to the existing flow patterns. The analysis reveals that the homogeneous model is suitable for dispersed bubbly flow whereas bubbly and churn‐turbulent flow pattern is better predicted by the drift flux model. On the other hand, the two fluid flow model accurately predicts the pressure drop in core annular flow.
Enhanced Boiling of Methanol on Copper Coated Surface
Authors: Prasad L. , Siraj Alam M. , Gupta S. C. , Agarwal V. K. 
Published: July 2007

AbstractThis paper presents an experimental investigation on nucleate pool boiling of saturated methanol on uncoated as well as copper‐coated mild steel heating tubes of various thicknesses at atmospheric and subatmospheric pressures. It also includes the effect of heat flux, pressure and coating thickness on the boiling heat transfer coefficient of coated tube surfaces. Heat flux was progressively increased from 15,670.20 to 43,151.57 W/m2 in six steps and pressure from 23.02 to 98.68 kN/m2 in five steps. Boiling characteristics on such surfaces are compared with those on uncoated ones. Also, a criterion for enhanced boiling of methanol on copper‐coated tubes is described.
Photocatalytic Oxidation of Isopropanol in Aqueous Solution Using Perovskite‐Structured La2Ti2O7
Authors: Ku Y. , Wang L.‐C. , Ma C.‐M. 
Published: July 2007

AbstractThis study is focused on the application of a highly‐doped layered perovskite, La2Ti2O7, as the photocatalyst for the photocatalytic decomposition of isopropanol (IPA). The La2Ti2O7 powder prepared by solid state reaction was characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), UV‐Vis diffuse reflectance spectrophotometry (UV‐DRS), X‐ray photoelectron spectroscopy (XPS), and zeta potential. The temporal behavior of the photocatalytic decomposition of IPA in aqueous solution by the UV/La2Ti2O7, with a photoreactor operated in a recirculation mode, was studied under various conditions including solution pH, light intensity, and La2Ti2O7 loading. The decomposition of IPA in aqueous solution by La2Ti2O7 photocatalytic processes was found to be technically feasible. A kinetic equation was developed for modeling the photocatalytic decomposition of IPA by the UV/La2Ti2O7 photocatalytic processes.
Exploration of the Binding Mode of Indanesulfonamides as Selective Inhibitors of Human Carbonic Anhydrase Type VII by Targeting Lys 91
Authors: Thiry Anne , Masereel Bernard , Dogné Jean‐Michel , Supuran Claudiu T. , Wouters Johan , Michaux Catherine 
Published: July 2007

AbstractConvulsions are common neurological disorders in clinical medicine and are triggered by several mechanisms. The enhancement of neuronal excitability can be related, among other factors, to GABAergic depolarization. Carbonic anhydrase (CA) VII contributes to this electrophysiological behavior by providing bicarbonate anion, which can mediate current through channels coupled to GABAA receptors. Among the cytosolic CAs, the mechanism of action and inhibition of CA VII is less understood. We present herein the pharmacological evaluation of both enantiomers of an indanesulfonamide compound substituted by a pentafluorophenyl moiety against CA VII and five other human CA isoforms to evaluate their selectivity. The investigated compounds are powerful inhibitors of hCA VII, with Ki values in the range of 1.7–3.3 nM, but their selectivity needs to be improved. A molecular modeling study was conducted to rationalize the structure–activity relationships and provide useful insight into the future design of selective hCA VII inhibitors.
Global existence for three‐dimensional incompressible isotropic elastodynamics
Authors: Sideris Thomas C. , Thomases Becca 
Published: July 2007

AbstractThe existence of global‐in‐time classical solutions to the Cauchy problem for incompressible, nonlinear, isotropic elastodynamics for small initial displacements is proved. The generalized energy method is used to obtain strong dispersive estimates that are needed for long‐time stability. This requires the use of weighted local decay estimates for the linearized equations, which are obtained as a special case of a new general result for certain isotropic symmetric hyperbolic systems. In addition, the pressure that arises as a Lagrange multiplier to enforce the incompressibility constraint is estimated as a nonlinear term. The incompressible elasticity equations are inherently linearly degenerate in the isotropic case; i.e., the equations satisfy a null condition necessary for global existence in three dimensions. © 2007 Wiley Periodicals, Inc.
Hodge genera of algebraic varieties I
Authors: Cappell Sylvain E. , Maxim Laurentiu G. , Shaneson Julius L. 
Published: July 2007

AbstractThe aim of this paper is to study the behavior of Hodge‐theoretic (intersection homology) genera and their associated characteristic classes under proper morphisms of complex algebraic varieties. We obtain formulae that relate (parametrized families of) global invariants of a complex algebraic variety X to such invariants of singularities of proper algebraic maps defined on X. Such formulae severely constrain, both topologically and analytically, the singularities of complex maps, even between smooth varieties. Similar results were announced by the first and third author in [13, 32]. © 2007 Wiley Periodicals, Inc.
Spectroscopic Fingerprints of Amine and Imide Functional Groups in Self‐Assembled Monolayers
Authors: Ruiz‐Osés Miguel , Kampen Thorsten , González‐Lakunza Nora , Silanes Iñaki , Schmidt‐Weber Philipp M. , Gourdon André , Arnau Andrés , Horn Karsten , Ortega J. Enrique 
Published: July 2007

AbstractThe electronic structures of naphthalene tetracarboxylic diimide (NTCDI) and 1,4‐bis(4,6‐diamino‐1,3,5‐triazin‐2‐yl)benzene (BDG) monolayer assemblies grown on Au(111) are investigated by photoemission spectroscopy, X‐ray absorption, and density functional theory. The different spectroscopic features in the absorption and core‐level photoemission spectra are understood in terms of contributions from different core and molecular levels at N‐ and O‐atom sites. This study provides clear spectroscopic fingerprints for amine and imide functional end groups, which drive the self‐organization process in a number of planar, π‐conjugated molecular structures.
Symbolic Analysis of Linear Non‐Reciprocal Circuits
Authors: Nitescu Miruna , Constantinescu Florin 
Published: July 2007

AbstractA symbolic expression of a transfer function in a linear non‐reciprocal circuit is proved; the symbolic parameters may be proper immittances and controlled source parameters. the effectiveness of computation of symbol product coefficients is improved by using a generation‐and‐test algorithm of symbol combinations. A comparison between the most efficient symbolic analysis methods and the proposed method is performed. It is concluded that the proposed method is competitive with these methods.
Higher‐order modelling of the diffusion dynamics in a bipolar transistor
Authors: Lehtinen Kari , Sipila Markku , Porra Veikko 
Published: July 2007

AbstractA higher‐order diffusion model for a bipolar transistor has been developed. This model is based on the Padé approximation of the quasi‐static expansions of the base and collector currents and gives improved accuracy for the simulation of fast transients and periodic operation at high frequencies. the effect of higher‐order circuit elements on accuracy is demonstrated by calculating the transient response to a step excitation and by determining the scattering parameters of a transistor model with higher‐order elements linearized about an operating point. the higher‐order model is replaced by an equivalent circuit including only conventional elements, and the transient behaviour of these two models is compared.
Noise and sensitivity optimization in the design of second‐order single‐amplifier filters
Authors: Bowron P. , Mezher K. A. 
Published: July 2007

AbstractSimultaneous optimization of the sensitivity and noise performance of second‐order single‐amplifier RC filter sections resolves a long‐standing discrepancy and reveals practical trade‐offs. the influences of controlled gain, component spread and design choice are elucidated for both bandpass and lowpass complementarily symmetrical circuits.
On Improved Representation Theorems For Multidimensional Lossless Bounded Matrices
Authors: Fettweis A. , Basu Sankar 
Published: July 2007

AbstractAn improved form of representation of multidimensional (k‐D) discrete lossless two‐ports in a form similar to the well‐known Belevitch canonical form of classical one‐dimensional network theory is presented. Representations of the transfer function matrix, chain matrix and hybrid matrix associated with discrete lossless multidimensional twoports are derived on the basis of our earlier result.An improved form of representation of multidimensional (k‐D) discrete lossless two‐ports in a form similar to the well‐known Belevitch canonical polynomial associated with the system. This fact is true for both discrete and continuous systems and apparently has remained unnoticed even in ID.
Neural network for non‐linear programming with linear equality constraints
Authors: Osowski Stanisłsaw 
Published: July 2007

AbstractThis paper presents a simplified approach to neural optimization in the presence of linear equality constraints. In contrast to the standard Lagrangian approach, the constraints simplify the final neural circuit instead of complicating it. the number of elements used is also significantly reduced. Instead of n + t integrators we need only n – t. There is also a similar saving in the number of preprocessing non‐linear devices. Elimination of the constraints allows a large speed‐up of the solution.
A collocation algorithm for calculating the periodic solutions of non‐linear oscillators
Authors: Buonomo A. 
Published: July 2007

AbstractAn approximation method is given for calculating the periodic solutions of non‐linear oscillators based upon the well‐known method of collocation, which belongs to the class of projection methods. Unlike available techniques, the method leads to a simple and efficient algorithmic procedure which consists of solving a system of non‐linear equations given in a simple explicit form.To demonstrate the effectiveness of the proposed algorithm, the results of some typical oscillator circuits are provided.
Perfect pairs of trees in graphs
Authors: Novak Ladislav , Gibbons Alan 
Published: July 2007

AbstractWe introduce the concept of perfect pairs of trees of a graph as a natural generalization of so‐called maximally distant pairs of trees. Several propositions and remarks are presented to display the properties of this new notion. Lemma 1, which plays a central role, gives five equivalent statements characterizing the relation ‘to be maximally distant from’ between pairs of trees. Symmetrization of this relation leads to our concept of a perfect pair of trees, the properties of which are given in Theorem 1. Remark 4 shows how naturally our new concept arises. Additionally, certain examples are provided to illustrate perfect pair structures in a graph.
Existence and stability of periodic solutions in weakly non‐linear electrical circuits via averaging and functional analytical methods
Authors: Ulmet D. E. 
Published: July 2007

AbstractThe method of averaging has been extensively used to detect invariant manifolds for non‐linear dynamical systems. In this paper we combine the averaging analysis with some functional analytical methods to prove the existence and stability of periodic solutions for a class of weakly non‐linear electrical circuits. We also prove a specific averaging theorem for these circuits using Gronwall estimates and the Sanchez‐Palencia summation trick. These results are applied to the model equations of a system of coupled Van der Pol oscillators to obtain the existence of orbitally asymptotically stable periodic solutions. Finally we construct asymptotic approximations of these solutions and perform a numerical simulation of the flow.
Programmable analogue vlsi cnn chip with local digital logic
Authors: Halonen K. , Porra V. , Roska T. , Chua L. 
Published: July 2007

AbstractA new integrated circuit cellular neural network implementation with digitally or continuously selectable template coefficients is presented. Local logic and memory are added into each cell, providing a simple dual (analogue and digital) computing structure. Variable gain OTAs are used as the voltage‐controlled current sources to programme the template element values. the cells have local switched feedback (both analogue and digital) to feed from the output to the input or state capacitor. Therefore this analogue array processor can be applied to solve problems with a sequence of different templates. A 4 × 4 CNN circuit is realized using the 2 μm analogue CMOS process.