bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analytic preconditioners for the electric field integral equation
Authors: Antoine X. , Bendali A. , Darbas M. 
Published: August 2004

AbstractSince the advent of the fast multipole method, large‐scale electromagnetic scattering problems based on the electric field integral equation (EFIE) formulation are generally solved by a Krylov iterative solver. A well‐known fact is that the dense complex non‐hermitian linear system associated to the EFIE becomes ill‐conditioned especially in the high‐frequency regime. As a consequence, this slows down the convergence rate of Krylov subspace iterative solvers. In this work, a new analytic preconditioner based on the combination of a finite element method with a local absorbing boundary condition is proposed to improve the convergence of the iterative solver for an open boundary. Some numerical tests precise the behaviour of the new preconditioner. Moreover, comparisons are performed with the analytic preconditioner based on the Calderòn's relations for integral equations for several kinds of scatterers. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis of macrocyclic aliphatic disulfide oligomers from dithiols by oxidative coupling with oxygen using a copper‐amine catalyst
Authors: Meng Y. Z. , Hllil A. R. , Hay A. S. 
Published: August 2004

AbstractA new effective method is provided for the synthesis of macrocyclic aliphatic disulfide oligomers by catalytic oxidation of aliphatic dithiols with oxygen in the presence of a copper‐amine catalyst. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis of saccharidic polymer colloids via free radical mini‐emulsion polymerization
Authors: Al‐Bagoury M. , Yaacoub E.‐J. 
Published: August 2004

AbstractPolymer colloids based on 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranose (3‐MDG) and butyl acrylate (BA) were prepared via free radical mini‐emulsion polymerization. The kinetic and colloidal features of the copolymerization were investigated. The final particle size (D) of the sugar latexes is inversely proportional to the concentration of the anionic emulsifier (sodium dodecyl sulphate, SDS) and the non‐ionic one (alkyl polyglucoside, APG). It was also found that D is independent of the concentration of either the water‐soluble initiator (potassium persulfate, KPS), or the oil‐soluble initiator (2,2′‐azobisisobutyronitrile, AIBN). The rate of mini‐emulsion polymerization is lower in comparison with the conventional emulsion polymerization under the same conditions. The polymerization rate (Rp) and the total number of particles (Np) are proportional to the 0.72th and 0.93th power of the SDS, and to the 1.40th and 2.22th of the APG concentration. Following reaction orders, 0.79/0.06 were obtained for Rp/Np versus the concentration of KPS, and 0.22/−0.01 for AIBN, respectively. Copyright © 2004 John Wiley & Sons, Ltd.
Dendritic polyisophthalate endcapped with naphthyl groups for holographic recording
Authors: Kou Huiguang , Shi Wenfang , Lougnot Daniel J. , Lu Yonghua , Ming Hai 
Published: August 2004

AbstractA novel dendritic polyisophthalate with 12 naphthyl groups at the chain ends was synthesized from 5‐hydroxyisophthalic acid as an AB2 monomer, 1,3,5‐benzenetricarbonyl trichloride as an ‘initiator core’ molecule, and β‐naphthol as an endcapping reagent, via a stepwise growth process. An average molecular weight of 2860 g mol−1, and a refractive index of 1.618 at 650 nm were obtained by gel permeation chromatography and ellipsometry, respectively. A photopolymerizable recording dry film incorporating this dendrimer as a polymeric binder was used for holographic recording. Diffraction gratings with diffraction efficiency exceeding 80%, together with a modulation index of 10−2 were obtained. Copyright © 2004 John Wiley & Sons, Ltd.
Epoxy resins from rosin acids: synthesis and characterization
Authors: Atta Ayman M. , Mansour R. , Abdou Mahmoud I. , Sayed Ashraf M. 
Published: August 2004

AbstractA series of multifunctional cycloaliphatic glycidyl ester and ether epoxy resins were synthesized by reaction of condensed rosin acid‐formaldehyde resins with epichlorohydrin. The chemical structure of the produced resins was determined by IR and 1H‐NMR analysis. The molecular weight of the produced resins was determined by gel permeation chromatography (GPC). A series of poly‐ (amide‐imide) hardeners were prepared from condensation of Diels–Alder adducts of rosin acid‐maleic anhydride and acrylic acid with triethylene tetramine and pentaethylene hexamine. These amines were also condensed with Diels–Alder adducts of rosin ketones. The curing exotherms of the produced epoxy resins with poly(amide‐imide) hardeners were investigated. The data of mechanical properties, solvent and chemical resistance indicate the superior adhesion of the cured epoxy resins. Copyright © 2004 John Wiley & Sons, Ltd.
High sensitivity and broad dynamic range infrared multiphoton dissociation for a quadrupole ion trap
Authors: Hashimoto Yuichiro , Hasegawa Hideki , Waki Izumi 
Published: August 2004

AbstractDynamic control of bath gas pressure in a quadrupole ion trap (QIT) achieved high sensitivity and broad dynamic range infrared multiphoton dissociation (IRMPD). Conventional IRMPD is not sensitive because the bath gas pressure in the QIT needs to be kept at less than 1 mTorr for an effective dissociation, whereas the pressure should be about 20 mTorr for maximum trapping efficiency during ion accumulation. By switching the bath gas pressure between about 20 mTorr during the ion accumulation period and less than 0.6 mTorr during the IRMPD period, it was possible to achieve both maximum trapping efficiency and effective IRMPD. An optimized method for gas introduction enables the trapping efficiency to remain constant during the accumulation period, which permits a broad dynamic range measurement. Copyright © 2004 John Wiley & Sons, Ltd.
Packet scheduling for the delivery of multicast and broadcast services over S‐UMTS
Authors: Karaliopoulos M. , Henrio P. , Narenthiran K. , Angelou E. , Evans B. G. 
Published: August 2004

AbstractWe investigate the packet‐scheduling function within the access scheme of a unidirectional satellite system providing point‐to‐multipoint services to mobile users. The satellite system may be regarded as an overlay multicast/broadcast layer complementing the point‐to‐point third generation (3G) mobile terrestrial networks. The satellite access scheme features maximum commonalties with the frequency division duplex (FDD) air interface of the terrestrial universal mobile telecommunications system (T‐UMTS), also known as wideband code division multiple access (WCDMA), thus enabling close integration with the terrestrial 3G mobile networks and cost‐efficient handset implementations. We draw our attention on one of the radio resource management entities relevant to this interface: the packet scheduler. The lack of channel‐state information and the point‐to‐multipoint service offering differentiate the packet scheduler in the satellite radio interface from its counterpart in point‐to‐point terrestrial mobile networks. We formulate the scheduler tasks and describe adaptations of two well‐known scheduling disciplines, the multilevel priority queuing and weighted fair queuing schemes, as candidates for the time‐scheduling function. Simulation results confirm the significance of the transport format combination set (TFCS) with respect to both the resource utilization achieved by the scheduler and the performance obtained by the flows at packet‐level. The performance gap of the two schemes regarding the fairness provided to competing flows can be narrowed via appropriate selection of the TFCS, whereas the achieved delay and delay variation scores are ultimately dependent on the packet‐level dynamics of individual flows. Copyright © 2004 John Wiley & Sons, Ltd.
System design, capacity dimensioning and revenue estimation for aeronautical communications via satellite
Authors: Werner Markus , Battaglia Lorenzo , Holzbock Matthias 
Published: August 2004

AbstractThe paper discusses various system aspects of commercial aeronautical broadband satellite communications (AirCom). An integrated global system design approach is presented, and key R&D issues along this path are discussed. Some focus is laid on geographic satellite coverage and constellation alternatives. A capacity dimensioning method for global aeronautical communications is developed, using a global flight database, and numerical results from computer simulations are presented. Finally, we estimate the revenues that airlines can expect from passenger telephone and Internet services offered on North Atlantic flights, under the assumption of an existing wireless cabin infrastructure, supporting wireless Internet and GSM telephony. Copyright © 2004 John Wiley & Sons, Ltd.
Salivary prekallikrein output during the ranger training‐induced stress
Authors: Tagashira Sumito , Yamaguchi Keiji , Matsunaga Tsunenori , Toda Kazuo , Hayashi Yoshihiko 
Published: August 2004

AbstractSaliva can be considered a mirror of the body, reflecting its general conditions. The present study was conducted to identify the changes in specific neurotransmitter and prekallikrein levels in saliva and the correlations between changes in neuroendocrine factors in plasma and saliva after intensive physical training of rangers of Japan Ground Self Defence Force (JGSDF). The subjects were 14 young uniformed males (aged 20–26 years old) who underwent ranger training under the control of the 4th Division of the JGSDF. Before training began and after 30 days of hard training, the levels of prekallikrein, β‐endorphin, serotonin, noradrenaline and dopamine in saliva and plasma were routinely measured. The level of prekallikrein in saliva was significantly increased after training, and the level of β‐endorphin in saliva showed an upward trend after the training. The level of prekallikrein in plasma showed a significant decrease after the training, while the level of β‐endorphin was unchanged. Average concentrations of values in serotonin, noradrenaline and dopamine in plasma were significantly increased after the training. These findings suggest that the comparison of levels of prekallikrein and β‐endorphin in saliva and plasma may give useful insights for the estimation of stress‐induced analgesia. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis, Magnetism, and Crystal Structure of Li2Fe[(PO4)(HPO4)] and its Hydrogen Position Refinement
Authors: Mi Jin‐Xiao , Borrmann Horst , Zhang Hui , Huang Ya‐Xi , Schnelle Walter , Zhao Jing‐Tai , Kniep Rüdiger 
Published: August 2004

AbstractLithium iron(III) monophosphate‐monohydrogen‐monophosphate, Li2Fe[(PO4)(HPO4)], was synthesized under mild hydrothermal conditions and its crystal structure was determined by single crystal X‐ray diffraction methods. Crystallographic data: monoclinic, P121/n1 (no. 14), a = 4.8142(2) Å, b = 7.9898(4) Å, c = 7.4868(4) Å, β = 104.398(3)°, V = 278.93(2) Å3, Z = 2, Dx = 3.104 g · cm‐3. The structure is characterized by FeO6 octahedra sharing common O‐corners with six neighbouring PO4 tetrahedra to form a three‐dimensional framework. Lithium cations are located within channels running along [100]. The channels are formed by eight‐membered rings resulting from the connection of alternating FeO6 octahedra (4×) and phosphate tetrahedra (4×). High‐resolution diffraction data allowed to refine a split model for the position of the hydrogen atom. Magnetization data confirm the valence state 3+ for iron and detect an antiferromagnetic ordering of the iron moments below 23.6 K. Thermal decomposition of the compound was investigated by DTA/TG methods.
Synthesis, Structure, and Lanthanide Derivatives of an Unusual Hexameric Alcohol: [2,4,6‐(CF3)3C6H2CH2OH]6
Authors: Edelmann Frank T. , Poremba Peter , Bohnen Frank Michael , Herbst‐Irmer Regine 
Published: August 2004

AbstractHitherto unknown 2,4,6‐tris(trifluoromethyl)benzyl alcohol (3) was synthesized in 41 % yield by treatment of freshly prepared RFLi (2) with paraformaldehyde (RF = 2,4,6‐tris(trifluoromethyl)phenyl). According to an X‐ray diffraction study the crystal structure of 3 consists of S6 symmetric cyclic hexamers [2,4,6‐(CF3)3C6H2CH2OH]6. Deprotonation of 3 with NaN(SiMe3)2 in toluene afforded the unsolvated sodium alkoxide derivative RFCH2ONa (4). Homoleptic lanthanide alkoxides of the type Ln(OCH2RF)3 (Ln = Nd (5), Sm (6), Yb (7)) were made by treatment of Ln(C5H5)3 with three equivalents of 3. Similar reactions in a 1:1 molar ratio afforded the bis(cyclopentadienyl)lanthanide alkoxide derivatives (C5H5)2Ln(OCH2RF) (Ln = Nd (8), Sm (9), Yb (10)).
Second‐Sphere Coordination of the Tris(5, 5′‐diamino‐2, 2′‐bipyridine)iron Complex With Arene‐Carboxylate Ligands Through N‐H···O Hydrogen Bonding
Authors: Yang Xiao‐Juan , Wu Biao , Janiak Christoph , Sun Wen‐Hua , Hu Huai‐Ming 
Published: August 2004

AbstractThe tris(5, 5′‐diamino‐2, 2′‐bipyridine)iron(II) complex [Fe(DABP)3]2+ can be engaged in hydrogen‐bonding interactions from the amino groups to carboxylate‐containing molecules as H‐bond acceptors. This so‐called second‐sphere coordination of the metal complex is investigated here by using benzene‐1, 4‐dicarboxylate (terephthalate, L1), benzene‐1, 3‐dicarboxylate (isophthalate, L2), biphenyl‐2, 2′‐dicarboxylate (L3), and benzene‐1, 3, 5‐tricarboxylate (trimesate, L4) anions for N‐H···O bonding. The second‐sphere coordination of [Fe(DABP)3]2+ is further complemented by water molecules of crystallization in the isolated and structurally elucidated compounds of [Fe(DABP)3](L1)·5H2O, [Fe(DABP)3](L2)·8H2O, [Fe(DABP)3](L3)·12.5H2O, and [Fe(DABP)3]3(L4)2·20H2O. The hydrogen‐bonding between [Fe(DABP)3]2+ and the dicarboxylate anions (L1‐L3) decreases from a three‐dimensional supramolecular network (with L1) to discrete units (with L2 and L3) with the increasing number of crystal water molecules. The tricarboxylate ligand L4 is capable of capping the triangular face formed by the three amino groups in [Fe(DABP)3]2+. The solid‐state structures of DABP·2H2O and 5, 5′‐bis(ethoxycarbonylamino)‐2, 2′‐bipyridine (BEBP) are reported.
Synthesis and Structure of a Neodymium Complex with the Nitrilotriacetate Ligand: [NdIII(nta)]n
Authors: Zhang Quan‐Zheng , Lu Can‐Zhong , Yang Wen‐Bin 
Published: August 2004

AbstractA neodymium complex, [Nd(nta)]n (1) (H3nta = nitrilotriacetic acid) was synthesized and characterized by X‐ray diffraction analysis. Compound 1 exhibits a three‐dimensional network, in which the NdIII ion is coordinated by one nitrogen atom and seven carboxyl oxygen atoms with dodecahedral coordination. One striking feature is that in the Nd coordination center there is no water ligand found.
Synthesis and Crystal Structures of Tris‐[3, 5‐bis(trifluoromethyl)phenyl]arsine Oxide at 293 and 100 K and the Localization of the Trifluoromethyl Groups
Authors: Dietzel Pascal D. C. , Jansen Martin 
Published: August 2004

AbstractTris[3, 5‐bis(trifluoromethyl)phenyl]arsine oxide (1) was synthesised by oxidation of tris[3, 5‐bis(trifluoromethyl)phenyl]arsine with hydrogen peroxide in acetone. At 293 K, it crystallizes in the trigonal space group R3c (a = 20.2947(12) Å, c = 11.2484(13) Å, Z = 6, R1 = 0.0254). The compound undergoes a phase transition upon cooling, and it crystallizes in the monoclinic space group Cc at 100 K (a = 13.8621(13) Å, b = 18.6537(17) Å, c = 11.2874(10) Å, Z = 4, R1 = 0.0444). The crystal structures of both phases were determined. The fluorine atoms of the trifluoromethyl groups are strongly disordered at room temperature, which probably indicates a rotational motion in the plane of the fluorine atoms. This motion slows down while lowering the temperature, and the fluorine atoms are localized at 100 K. This point is illustrated by comparison of the experimental electron densities at the CF3 groups. The packing pattern in both structures consists of parallel columns of ecliptically stacked molecules. The columns are hexagonally arranged.
The First Hexa‐coordinated Tetranuclear Nickel Complex {[Ni(en)2]4[H4L]}(ClO4)4·7H2O with Tetrakis‐bidentate Oxamato Bridge
Authors: Liang Mao , Zhu Li‐Na , Liu Shi‐Xiong , Liao Dai‐Zheng , Jiang Zong‐Hui , Yan Shi‐Ping , Cheng Peng 
Published: August 2004

AbstractThe first tetranuclear nickel complex with the oxamato ligand, {[Ni(en)2]4[H4L]}(ClO4)4·7H2O (1) (L = N, N′, N″, N‴‐methanetetrayltetrakismethylenetetrakis (oxamato)), has been prepared and determined by single‐crystal X‐ray analysis. 1 crystallizes in the tetragonal space group I41/a, with a = 15.2744(9), c = 31.3748(2) Å and Z = 4. Each nickel (II) ion is in a distorted octahedral donor atom environment, which comprises four nitrogen atoms of two en molecules and two oxygen atoms of oxamato bridge. The shape of the entity looks like a propeller. The temperature‐dependent magnetic susceptibilities were analyzed by the Curie‐Weiss law; the following values were found C = 4.36 cm3 K mol‐1, θ = ‐24.7 K, respectively.
Partial and Gradual Hydrolysis of 2,2′‐Biimidazoline upon Coordination to Metal Ions, yielding New Chelating Ligands ‐ Synthesis, Characterization and X‐ray Structure of two Examples with Cobalt(III) and Copper(II)
Authors: van Albada Gerard A. , Mohamadou Aminou , Manotti Lanfredi Anna Maria , Mutikainen Ilpo , Turpeinen Urho , Ugozzoli Franco , Reedijk Jan 
Published: August 2004

AbstractThe synthesis, a full structural characterization of two transition‐metal compounds obtained by in‐situ hydrolysis and partly hydrolysis of the ligand 2, 2′‐biimidazoline (abbreviated as biz) is reported. When the biz ligand is completely hydrolysed the compound, N, N′‐bis(2‐aminoethyl)oxamide (abbreviated as H2oxen) is obtained, while the partial hydrolysis results in the ligand N‐(2‐aminoethyl)imidazoline‐2‐carboxamide (abbreviated as Hoxim).The CoIII ion in the mononuclear CoIII compound, [Co(biz)(oxim)(NCS)](ClO4)(C2H5OH)1/6(H2O)1/6 (1), has an octahedral coordination consisting of 6 nitrogen atoms with a distance varying from 1.889(6) to 1.950(5) Å. Two nitrogen atoms originating from a biz molecule, 3 nitrogen atoms are from the oxim ligand and one nitrogen is from the thiocyanate anion.Each CuII ion in the dinuclear CuII compound, [Cu2(H2oxen)(oxim)2(C2H5OH)2] (ClO4)2 (2), has a slightly distorted square‐pyramidal structure of which the basal plain consists of3 nitrogen atoms of the oxim ligand and one nitrogen atom of the H2oxen ligand, which is used as a “spacer” connecting the second CuII atom, with Cu‐N distances which vary from 1.944(2) to 2.037(2) Å. The apical position is formed by the oxygen atom of a semi‐coordinating ethanol molecule with a Cu‐O distance of 2.446(2) Å. The compounds are characterized by elemental analysis, ligand field, infrared and, for the CuII ion, also by EPR spectroscopy.
Synthesis and Crystal Structure of Na7Cu3O8, Containing a New Type of Oxocuprate(III) Oligoanion
Authors: Sofin Mikhail , Peters Eva‐Maria , Jansen Martin 
Published: August 2004

AbstractNa7Cu3O8 was prepared through oxidation of a Na3CuO2/NaCuO mixture (2:1) in dried oxygen at 450 °C. Single crystals have been grown by annealing of Na7Cu3O8, in the presence of Na2O2, at 450 °C for 2000 h in silver crucibles, which were sealed in glass ampoules under dried Ar. According to the X‐ray analysis of the crystal structure ($P {\bar 1}$, Z = 1, a = 5.5891(2), b = 6.0945(2), c = 7.8890(3) Å, α = 110.059(2), β = 108.669(2), γ = 90.237(2)°) a new Cu3O87‐ oxocuprate anion, consisting of three edge sharing CuO4 squares, is the prominent structural feature. These anions are aligned parallel to the space diagonal of the unit cell and can be regarded as infinite chains from which every fourth copper atom has been removed. This new representative of an oxocuprate(III) anion gives support to the expectation that the gap between dimeric and infinite edge sharing units of square planar cuprate anions can be closed, in principle.
[M(μ‐O2C‐C6H4‐CO2)(NH3)2] (M = Cu, Cd; O2C‐C6H4‐CO2 = benzene‐1, 4‐dicarboxylate, terephthalate): 1D Coordination Polymers with Strong Inter‐Chain Hydrogen Bonding
Authors: Paul Barbara , Zimmermann Boris , Fromm Katharina M. , Janiak Christoph 
Published: August 2004

AbstractCompounds [M(μ‐O2C‐C6H4‐CO2)(NH3)2] crystallize as straight‐ (M = Cu) and kinked‐chain (M = Cd) coordination polymers through the bridging action of the bis‐mono (Cu) and bis‐bidentate (Cd) benzene‐1, 4‐dicarboxylate (terephthalate) ligand. N‐H···O hydrogen bonding connects the chains to a three‐dimensional supramolecular network. Thermogravimetry shows the compounds to be stable up to 255 °C (M = Cu) and 70 °C (M = Cd) where decomposition starts with the loss of one ammin ligand. [Cd(μ‐O2C‐C6H4‐CO2)(NH3)2] exhibits a luminescence with λem, max = 392 nm (λex = 240 nm) on the same order of magnitude as Na2(O2C‐C6H4‐CO2).
Trovacene Chemistry. 10 [1] The [1]‐ and [2]Silatrovacenophanes (η7‐$\overline{C 7H6)V(η5‐C5H4S}$iR2) and (η7‐$\overline{C 7H6)V(η5‐C5H4SiR2S}$iR2 (R = Me, Ph): Synthesis, Structure, and Ring Opening
Authors: Elschenbroich Christoph , Paganelli Francesca , Nowotny Mathias , Neumüller Bernhard , Burghaus Olaf 
Published: August 2004

AbstractHeteroannular dilithiation of trovacene, (η7‐C7H7)V(η5‐C5H5) (1˙), and subsequent reaction with the respective dichlorosilane yielded the [1]silatrovacenophanes (η7‐$\overline{C 7H6)V(η5‐C5H4S}$iR2) (2˙, R = Ph; 3˙, R = Me) and the [2]silatrovacenophane (η7‐$\overline{C 7H6)V(η5‐C5H4SiMe2S}$iMe2) (4˙). Structural studies by X‐ray diffraction revealed sandwich tilt angles of 17.3° (2˙) and 3.8° (4˙), respectively, and considerable strain in the ring‐link‐ring region. EPR spectroscopy responds to these distortions in that the g‐tensor is tetragonal (gx = gy ≠ gz) for 4˙ but rhombic (gx ≠ gy ≠ gz) for 2˙ and 3˙. With increasing tilt, <g> increases slightly towards gfs = 2.0023 and a(51V) decreases, the latter response to tilting being more pronounced. These trends are plausible in view of distortion‐induced mixing of the V(3d) SOMO with ligand π orbitals. Whereas cyclic voltammetry of undistorted 4˙ displays reversible oxidation and reduction, the strained sandwich 2˙ shows irreversible behavior, probably caused by cleavage of the interannular bridge. [1]Silatrovacenophanes are thermally more robust than [1]silaferrocenophanes in that 2˙, exposed to 280 °C, fails to show indications of ring‐opening polymerization (ROP).
Dimeric Rhenium(I) Carbonyl Complexes with Thiosemicarbazone Backbone
Authors: Pereiras‐Gabián G. , Vázquez‐López E. M. , Abram U. 
Published: August 2004

AbstractDimeric, neutral rhenium(I) complexes of the composition [Re2(CO)6X(LR)] (X = Cl or Br) are formed when [NEt4]2[Re(CO)3Br3] or [Re(CO)3Cl(CH3CN)2] react with 2, 2′‐dipyridylketone thiosemicarbazones (HLR, R = H, Ph). The thiosemicarbazones deprotonate during the reaction and connect two tricarbonylrhenium(I) units as formally pentadentate bridging ligands. This results in an extremely rare coordination mode, in which the two nitrogen atoms of the hydrazone unit bind to each one of the rhenium atoms. The bond lengths inside the thiosemicarbazonato backbone reflect a large degree of delocalization of electron density.