bluuebunny/crossref_metadata_2025 huggingface dataset:
X‐ray structure of ILL2, an auxin‐conjugate amidohydrolase from Arabidopsis thaliana
Authors: Bitto Eduard , Bingman Craig A. , Bittova Lenka , Houston Norma L. , Boston Rebecca S. , Fox Brian G. , Phillips George N.
Published: June 2008

The plant hormone indole‐3‐acetic acid (IAA) is the most abundant natural auxin involved in many aspects of plant development and growth. The IAA levels in plants are modulated by a specific group of amidohydrolases from the peptidase M20D family that release the active hormone from its conjugated storage forms. Here, we describe the X‐ray crystal structure of IAA‐amino acid hydrolase IAA‐leucine resistantlike gene 2 (ILL2) from Arabidopsis thaliana at 2.0 Å resolution. ILL2 preferentially hydrolyses the auxin‐amino acid conjugate N‐(indol‐3‐acetyl)‐alanine. The overall structure of ILL2 is reminiscent of dinuclear metallopeptidases from the M20 peptidase family. The structure consists of two domains, a larger catalytic domain with three‐layer αβα sandwich architecture and aminopeptidase topology and a smaller satellite domain with two‐layer αβ‐sandwich architecture and α–β‐plaits topology. The metal‐coordinating residues in the active site of ILL2 include a conserved cysteine that clearly distinguishes this protein from previously structurally characterized members of the M20 peptidase family. Modeling of N‐(indol‐3‐acetyl)‐alanine into the active site of ILL2 suggests that Leu175 serves as a key determinant for the amino acid side‐chain specificity of this enzyme. Furthermore, a hydrophobic pocket nearby the catalytic dimetal center likely recognizes the indolyl moiety of the substrate. Finally, the active site of ILL2 harbors an absolutely conserved glutamate (Glu172), which is well positioned to act as a general acid‐base residue. Overall, the structure of ILL2 suggests that this enzyme likely uses a catalytic mechanism that follows the paradigm established for the other enzymes of the M20 peptidase family. Proteins 2009. © 2008 Wiley‐Liss, Inc.
Vibrational properties in nanocrystalline nickels: temperature effects and composite model for thermodynamics
Authors: Tang Jian‐Feng , Li Xue‐Song , Long Wo‐Yun , Wang Yong
Published: June 2008

Based on the atomic local structure, a nanocrystalline material is separated into two parts: inner grains and grain boundaries. Molecular dynamics simulations have been performed to study the difference in their vibrational properties in nanocrystalline nickels. The results obtained reveal that a similar phonon frequency softening as in the perfect lattice mainly focuses on grains in nanocrystalline materials, and for the grain boundary part there is no obvious change in the vibrational density of states in the temperature range 300–900 K, especially in the lower frequency range. Comparing with conventional crystals, the higher specific heat and vibrational entropy, and lower vibrational free energy with decreasing mean grain size, result from the high proportion of grain boundaries in nanocrystals. In addition, the composite model provides a good description of the contributions of grain and grain boundary phases to thermodynamic quantities. Supposing the nanocrystalline material can be treated as a composite composed of grain and grain boundary network, the vibrational thermodynamic quantities of the system can be well determined from the proportion of grain boundaries and the corresponding thermodynamic quantities of grain and grain boundary parts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of temperature on the magnetic properties of Fe3O4 thin films studied by ferromagnetic resonance (FMR)
Authors: Budak S. , Yildiz F. , Ozdemir M. , Aktas B.
Published: June 2008

Single crystalline Fe3O4 thin films of 110 Å thickness grown on MgO (100) substrate have been investigated by Ferromagnetic Resonance (FMR) technique as a function of temperature between 3 and 300 K. A strong unidirectional (exchange) anisotropy field was detected as evidence from a shift of the resonance field for the r‐FC case relative to that for n‐FC case at lower temperature. Using a field‐induced unidirectional exchange and bulk anisotropy, with the usual magneto‐crystalline cubic anisotropy energy, we have simulated both the experimental spectra and angular dependence of resonance field to deduce anisotropy and other magnetic parameters as a function of temperature. Magnetic parameters and Verwey transition for the thin film case were found to shift down to around 90 K from 120 K for bulk sample of the same compound as well. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Density functional study of graphene overlayers on SiC
Authors: Mattausch Alexander , Pankratov Oleg
Published: June 2008

Despite the ongoing “graphene boom” of the last three years our understanding of epitaxial graphene grown on SiC substrate is only beginning to emerge. Along with experimental methods such as low energy electron diffraction (LEED), scanning tunneling microscopy (STM) and angle resolved photoemission spectroscopy (ARPES), ab initio calculations help to uncover the geometric and electronic structure of the graphene/SiC interface. In this chapter we describe the density‐functional calculations we performed for single and double graphene layers on Si‐ and C‐terminated 6H‐SiC surfaces. Experimental data reveal a pronounced difference between the two surface terminations. On a Si‐terminated surface the interface adopts a 6√3 × 6√3 unit cell whereas the C‐face supports misoriented (turbostratic) graphene layers. It has been recently realized that, on the Si‐face, the large commensurate cell is subdivided into patches of coherently matching to the substrate carbon atoms. In our calculations we assumed the “coherent match” geometry for the whole interface plane. This reduces the periodic unit to the √3 × √3R 30° cell but requires a substantial stretching of the graphene sheet. Although simplified, the model provides a qualitative picture of the bonding and of the interface electron energy spectrum. We find that the covalent bonding between the carbon layer and the substrate destroys the massless “relativistic” electron energy spectrum, the hallmark of a freestanding graphene. Hence the first carbon layer cannot be responsible for the graphene‐type electron spectrum observed by ARPES and rather plays a role of a buffer between the substrate and the subsequent carbon sheets. The “true” graphene spectrum appears with the second carbon layer which exhibits a weak van der Waals bonding to the underlying structure. For Si‐terminated substrate, we find that the Fermi level is pinned by the interface state at 0.45 eV above the graphene Dirac point, in agreement with experimental data. This renders the interface metallic. On the contrary, for a C‐face the “coherent match” model predicts the Fermi level exactly at the Dirac point. However, this does not necessarily apply to the turbostratic graphene layers that normally grow on the C‐terminated substrate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Identification of intrinsic defects in SiC: Towards an understanding of defect aggregates by combining theoretical and experimental approaches
Authors: Bockstedte Michel , Gali Adam , Mattausch Alexander , Pankratov Oleg , Steeds John W.
Published: June 2008

In SiC, mobile point defects may form thermally stable clusters and aggregates, such as di‐vacancies or carbon interstitial complexes. Although predicted by theory, experimental evidence of such clusters became available only recently. Combining theoretical and experimental approaches, the unique identification of the di‐vacancy, the carbon vacancy‐antisite complex with the spin resonance centers P6/P7 and SI5 was recently achieved. In this way also the di‐carbon and tri‐carbon antisites with the photoluminiscence centers P–T and U, HT3 and HT4, respectively were identified. The two identified vacancy complexes show distinct properties: while the di‐vacancy, like the silicon vacancy possesses a high‐spin ground state, the carbon vacancy–antisite complex, like the carbon vacancy, is a Jahn–Teller center. These effects consistently explain the complex properties of the spin resonance spectra and are discussed in detail for the isolated vacancies. The aggregation of vacancies proved to be relevant in the explantation of the kinetic deactivation of nitrogen in co‐implanted SiC. This and further evidence for defect aggregates underline the relevance of this notion. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Present status and future prospects for electronics in electric vehicles/hybrid electric vehicles and expectations for wide‐bandgap semiconductor devices
Authors: Hamada Kimimori
Published: June 2008

Toyota refers to the ability of users to continuously enjoy the convenience provided by automobiles as ‘sustainable mobility’. In order to achieve this, we are carrying out the endless challenge of minimizing the negative aspects of automobiles, such as CO2emissions, air pollution, traffic fatalities, and congestion, while maximizing automobile comfort, enjoyment, and excitement. In the area of the environment, we believe that we can come closer to creating the ‘ultimate ecovehicle’ by increasing the environmental performance of the power train, utilizing new fuels and electrical energy, and integrating hybrid technology into all of the results. In the Toyota Group, we think that power electronics is a key technology for the automotive technology of the future. We have defined SiC and GaN as core items for breakthroughs in power electronics technologies for the future, and we are energetically pursuing research and development in those areas. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of an intermediate graphite layer on the electronic properties of metal/SiC contacts
Authors: Reshanov Sergey A. , Emtsev Konstantin V. , Speck Florian , Gao Kun‐Yuan , Seyller Thomas K. , Pensl Gerhard , Ley Lothar
Published: June 2008

Photoelectron spectroscopy and electrical measurements were used to study the graphite/SiC‐interface with emphasis on the Schottky barrier formation. The investigations revealed a strong dependence of the Schottky barrier height on the surface polarity of SiC. In the case that the graphite layer was prepared on the Si(0001)‐face of n‐/p‐type 4H‐ and n‐/p‐type 6H‐SiC, the Fermi level is pinned close to the conduction band edge at the interface. The Schottky barrier fabricated on n‐type 4H‐SiC (0001) is 0.6 eV, whereas on n‐type 6H‐SiC (0001) it is lower and amounts (0.3–0.55) eV. On p‐type 4H‐/6H‐SiC, the Schottky barrier is 2.6 eV and (2.3–2.7) eV, respectively. When the Schottky barrier is prepared on the C‐face (000$ \bar 1 $) of n‐type 6H‐SiC, the Fermi level is pinned close to the middle of the band gap. In this case, the Schottky barrier height is found to be equal to 1.4 eV. It is demonstrated that the carbon/graphite formation at the interface between metal and n‐type 4H‐SiC does not ensure ohmic behavior. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐ and nanomechanical structures for silicon carbide MEMS and NEMS
Authors: Zorman Christian A. , Parro Rocco J.
Published: June 2008

Silicon carbide (SiC) is recognized as the leading semiconductor for high power and high temperature electronics owing to its outstanding electrical properties combined with mature processing technologies for monolithic structures. SiC has long been known for its outstanding mechanical and chemical properties making it equally attractive for mechanical structures in micro‐ and nanoelectromechanical systems (MEMS and NEMS). Recent advancements in bulk and surface micromachining have led to the development of SiC analogues to common Si‐based devices (i.e., resonators, pressure sensors). This paper presents an overview of MEMS and NEMS technologies that incorporate SiC as a key component in their mechanical structure, providing both a historical perspective as well as recent developments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial graphene: a new material
Authors: Seyller Th. , Bostwick A. , Emtsev K. V. , Horn K. , Ley L. , McChesney J. L. , Ohta T. , Riley J. D. , Rotenberg E. , Speck F.
Published: June 2008

Graphene, a two‐dimensional sheet of sp2‐bonded carbon arranged in a honeycomb lattice, is not only the building block of fullerenes, carbon nano tubes (CNTs) and graphite, it also has interesting properties, which have caused a flood of activities in the past few years. The possibility to grow graphitic films with thicknesses down to a single graphene layer epitaxially on SiC{0001} surfaces is promising for future applications. The two‐dimensional nature of epitaxial graphene films make them ideal objects for surface science techniques such as photoelectron spectroscopy, low‐energy electron diffraction, and scanning probe microscopy. The present article summarizes results from recent photoemission studies covering a variety of aspects such as the growth of epitaxial graphene and few layer graphene, the electronic and structural properties of the interface to the SiC substrate, and the electronic structure of the epitaxial graphene stacks. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface morphology and growth mechanism of catalyst‐free ZnO and Mgx Zn1–xO nanorods
Authors: Kim Miyoung , Hong Young Joon , Yoo Jinkyoung , Yi Gyu‐Chul , Park Gyeong‐Su , Kong Ki‐jeong , Chang Hyunju
Published: June 2008

High‐resolution transmission electron microscopy was employed to investigate morphologies and catalyst‐free growth mechanism of ZnO/Mgx Zn1–x O ‘multi‐quantum well’ and ‘core‐shell’ nanorod heterostructures as well as ZnO nanorods. The one‐dimensional growth mechanism and the hexagonal faceting of ZnO nanorod were explained by the surface energy anisotropy. The morphology change by alloying with Mg was successfully explained by investigating the energy gain by adatom adsorption and the reduction in the surface energy anisotropy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of polar organophosphorus pesticides in water samples by hydrophilic interaction liquid chromatography with tandem mass spectrometry
Authors: Hayama Tadashi , Yoshida Hideyuki , Todoroki Kenichiro , Nohta Hitoshi , Yamaguchi Masatoshi
Published: June 2008

A method combining hydrophilic interaction liquid chromatography (HILIC) with tandem mass spectrometry (MS/MS) was developed for the determination of polar organophosphorus pesticides (OPPs; acephate, methamidophos, monocrotophos, omethoate, oxydemeton‐methyl, and vamidothion) in water samples. To extract the polar OPPs and minimize matrix effects from the water sample, an activated carbon cartridge was used for pretreatment. After pretreatment of the water sample, the eluate from the activated carbon cartridge was directly injected into the HILIC/MS/MS system. The OPPs were separated on an Atlantis HILIC silica column by isocratic elution with a mixture of acetonitrile, isopropanol, and ammonium formate buffer as a mobile phase, and they were detected by positive electrospray ionization MS/MS in the selected reaction monitoring mode. The method was validated at 0.05, 0.5, and 5 µg/L levels in water samples, and the recoveries of polar OPPs were between 76.4 and 98.6%. The limits of detection were between 0.13 and 1.0 pg on‐column, and the limits of quantification were between 0.43 and 3.4 pg on‐column. The method can be applied to the determination of trace amounts of OPPs in environmental water samples. Copyright © 2008 John Wiley & Sons, Ltd.
Identification of low molecular weight carbohydrates employing new binary mixtures for matrix‐assisted laser desorption/ionisation mass spectrometry
Authors: Hashir Muhammad Ahsan , Stecher Guenther , Bonn Guenther K.
Published: June 2008

Various energy‐absorbing substances, aminopyrazine (AP), 4,4'‐azodianiline (ADA), and 1‐chloro‐4‐hydroxyisoquinoline (CHIQ), together with their binary mixtures with existing acidic MALDI matrices were subjected to matrix‐assisted laser desorption/ionisation mass spectrometry (MALDI‐MS) and evaluated for the analysis of low molecular weight carbohydrates. The newly introduced systems, especially AP and the combination of 2,5‐dihydroxybenzoic acid and aminopyrazine (DHB‐AP), have solved almost all the existing problems of the generally low sensitivity of carbohydrate analysis and of the strong background noise produced from single acidic matrices. In fact, especially at a mixing ratio of 3:1 (DHB/AP), outstanding results could be achieved, enabling the detection of analytes down to a concentration of 4 fmol/µL with mass accuracy of 37 ppm. The performance of the system was finally proven by analysing dextrins and biological samples each of which showed excellent signal intensity and signal‐to‐noise ratio. Copyright © 2008 John Wiley & Sons, Ltd.
Dynamic resource allocation for DVB‐RCS networks
Authors: Petraki Dionysia K. , Anastasopoulos Markos P. , Cottis Panayotis G.
Published: June 2008

To provide high‐speed multimedia services using the digital video broadcasting‐return channel satellite (DVB‐RCS) standard, it is imperative to efficiently assign timeslots according to user demands and dynamically take into account the variations of the propagation conditions. In satellite networks operating above 10 GHz, rain fading constitutes the dominant factor deteriorating the quality of service. In this paper, a novel two‐phase resource allocation scheme for a DVB‐RCS compliant satellite network is proposed. The scheme operates in two phases, the resource calculation and the resource assignment. In the resource calculation phase, based on a dynamic channel model, an efficient algorithm is presented to determine the superframe design that maximizes system throughput. In the resource assignment phase, a novel Hybrid Bin‐packing algorithm is introduced maximizing the utilization of the multi‐frequency time division multiple access frame. The proposed algorithm has been compared with existing schemes exhibiting significantly better results with regard to overall system throughput. Copyright © 2008 John Wiley & Sons, Ltd.
Two Three‐Dimensional Metal‐Organic Frameworks Constructed from Alkaline Earth Metal Cations (Sr and Ba) and 5‐Nitroisophthalicacid – Synthesis, Charaterization, and Thermochemistry
Authors: Chen Sanping , Shuai Qi , Gao Shengli
Published: June 2008

Two MOFs of [SrII(5‐NO2‐BDC)(H2O)6] (1) and [BaII(5‐NO2‐BDC)(H2O)6] (2) have been synthesized in water using alkaline earth metal salts and the rigid organic ligand 5‐NO2‐H2BDC. The compounds were characterized by elemental analysis, infrared spectrum, thermal analysis, and X‐ray crystallography. Crystal structure analyses have shown that the two complexes are isostructural as evidenced by IR spectra and TG‐DTA. Both compounds present three‐dimensional frameworks built up from infinite chains of edge‐sharing twelve‐membered rings through O–H···O hydrogen bonds. The specific heat capacities of the title complexes have been determined by an improved RD496‐III microcalorimeter with the values of (109.29 ± 0.693) J mol−1 K−1 and (81.162 ± 0.858) J mol−1 K−1 at 298.15 K, and the molar enthalpy changes of the formation reactions of complexes at 298.15 K were calculated as (4.897 ± 0.008) kJ mol−1 and (2.617 ± 0.009) kJ mol−1, respectively.
Polysulfonylamine. CLXXXIV. Kristallstrukturen molekularer Triphenylphosphangold(I)‐di(4‐X‐benzolsulfonyl)‐amide: Isomorphie und dichte Packung (X = Me, F, Cl, NO2) vs. struktursteuernde Halogenbrücken C–X···Au/O (X = Br, I)
Authors: Wölper Christoph , Roca Piñol Silvia , Durán Ibáñez Sara , Freytag Matthias , Jones Peter G. , Blaschette Armand
Published: June 2008

Polysulfonylamines. CLXXXIV. Crystal Structures of Molecular Triphenylphosphanegold(I) Di(4‐X‐benzenesulfonyl)amides: Isomorphism and Close Packing (X = Me, F, Cl, NO2) vs. Structure‐Determining C–X···Au/O Halogen Bonds (X = Br, I)

In order to study the structure‐determining influence that halogen bonding can exert during the course of crystallization, solid‐state structures are compared for two previously reported and four new molecular gold(I) complexes of the type Ph3P–Au–N(SO2–C6H4–4‐X)2, each featuring linear P,N coordination at gold and two phenyl rings with varying p‐substituents X = Me, F, Cl, NO2, Br or I. The compounds were synthesized by reactions of Ph3PAuX (X = Cl or I) with the corresponding silver di(arenesulfonyl)amides, crystallized from dichloromethane, and characterized by low‐temperature X‐ray diffraction. The Me, F, Cl and NO2 congeners are isomorphic and crystallize without solvent inclusion in the chiral orthorhombic space group P212121 (Z′ = 1). These structures are governed by isotropic close packing via three‐dimensional 21 symmetry, incidentally supported by an invariant set of C–H···O=S hydrogen bonds, CH/π interactions and π/π stackings of aromatic rings; in particular, the hard halogen atoms of the fluoro and the chloro homologues are not involved in X···Au, X···O or X···X interactions. The higher homologues, with soft halogen atoms, were obtained as a dichloromethane hemisolvate for X = Br and a corresponding monosolvate for X = I, each triclinic in the centrosymmetric space group $P{\bar 1}$ (Z′ = 1). Here, the primary structural effect is implemented by infinite chains in which translation‐related molecules are connected for the bromo compound by a bifurcated Au···Br(2)···O=S interaction, for the iodo congener by an equivalent Au···I(2)···O=S interaction and a short halogen bond C–I(1)···O=S. The latter bond is stronger than a similar C–Br···O=S interaction and induces a conformational adjustment of the (CSO2)2N group from the normal twofold symmetry in the bromo compound to an energetically unfavourable asymmetric form in the iodo homologue. In both cases, pairs of antiparallel molecular catemers are associated into strands via sixfold phenyl embraces, the strands are stacked to form layers, the solvent molecules are intercalated between adjacent layers, and the crystal packings are reinforced by a number of C–H···O=S hydrogen bonds and interactions of aromatic rings.
Crystal Structure of Ammonium Catena‐polyphosphate IV [NH4PO3]x
Authors: Sedlmaier Stefan J. , Schnick Wolfgang
Published: June 2008

Phase‐pure ammonium catena‐polyphosphate IV [NH4PO3]x was synthesized by heating NH4H2PO4 in a tube furnace under an ammonia gas flow. The product contained single crystals of [NH4PO3]x IV appropriate for an X‐ray structure determination enabling structure refinement of this compound. The pseudo‐merohedrally twinned crystals of [NH4PO3]x crystallize in the monoclinic crystal system (P21/c, no. 14, a = 2270.3(5), b = 458.14(9), c = 1445.1(3) pm, β = 108.56(3)°, Z = 4, 2264 data, R1 = 0.076). In the unit cell the catena‐polyphosphate chain anions run parallel [010] with a chain‐periodicity P = 2 and a stretching factor fs = 0.94. The chain anions are interconnected through extensive hydrogen bonding towards the ammonium ions. Due to ‘chemical twinning’ a novel catena‐polyphosphate structure type is realized in [NH4PO3]x IV. The vibrational spectra of [NH4PO3]x IV are reported as well.
Synthesis and X‐ray Crystal Structures of Acenaphthenequinone‐based α‐Diimine Palladium Complexes and a Novel V‐shape Tripalladium Cluster
Authors: Zhou Jin , Sun Hongjian , Harms Klaus , Sundermeyer Jörg
Published: June 2008

Partially fluorinated 1,4‐Diazadiene (α‐Diimine) ligand 3,5‐CF3‐BIAN (1) formed from 3,5‐bis(trifluoromethyl)aniline and acenaphthenequinone was used in the synthesis of palladium dichlorido complex 2 and its mono methyl chlorido palladium complex 3. Both complexes as well as side products of the reaction with methyl lithium such as trans‐bis(3,5‐bis(trifluoromethyl)aniline complex 4 and an interesting mixed valent trinuclear V‐shaped palladium cluster 5 with two bridging μ2,η3‐N,CN′ non‐innocent BIAN ligands were structurally characterized by the single‐crystal XRD method.
Earth Alkaline Tetrathiosquarates. II. – Syntheses and Crystal Structures of SrC4S4·4 H2O and Ba4K2(C4S4)5·16 H2O
Authors: Beck Johannes , Ben‐Amer Younis
Published: June 2008

Concentrated aqueous solutions of strontium chloride and barium chloride, respectively, allow on addition of the potassium salt of tetrathiosquarate, K2C4S4·H2O, the isolation of the earth alkaline salts SrC4S4·4 H2O (1) and Ba4K2(C4S4)5·16 H2O (2), both as dark red crystals. The crystal structure determinations (1: orthorhombic, Pnma, a = 8.149(1), b = 12.907(2), c = 10.790(2) Å, Z = 4; 2: orthorhombic, Pbca, a = 15.875(3), b = 21.325(5), c = 16.119(1) Å, Z = 4) show the presence of C4S42− ions with only slightly distorted D4h symmetry having average C–C and C–S bond lengths of 1.41Å and 1.681Å for 1 and 1.450Å and 1.657Å for 2. The structure of 1 contains concatenated edge‐sharing Sr(H2O)6S2 polyhedra. The Sr2+ ions are in eight‐fold coordination with Sr–O distances of 2.50–2.72Å and Sr–S distances of 3.21Å, (C4S4)2− acts as a chelating ligand towards Sr2+. The structure is closely related to the previously reported Ca2+ containing analogue, which is of lower symmetry belonging to the monoclinic crystal system. A supergroup‐subgroup relation between the space groups of both structures is present. The structure of 2 is made up of Ba2+ and K+ ions in eight and nine‐fold coordination by H2O molecules and (C4S4)2− ions which act as chelating ligands towards one cation and bridging between two cations. The coordination polyhedra of the cations are connected by common edges and corners in two dimensions to layers which are connected by tetrathiosquarate ions to a three‐dimensional network. The infrared and Raman spectra show bands typical for the molecular building units of the two compounds.
Hydrothermal Synthesis and X‐ray Crystal Structure of Four Inorganic‐Organic Hybrid Compounds in Vanadium /Copper Iodate Family
Authors: Liu Xiaomin , Li Guanghua , Bi Minghui , Hu Yawei , Yu Yang , Shi Zhan , Feng Shouhua
Published: June 2008

Four inorganic‐organic hybrid compounds with the formulae (1,10‐phen)(VO2)(IO3) (1), (2,2′‐bipy)(VO2)(IO3) (2), [Cu3(2,2′‐bipy)3Cl3(IO3)2]·I1.5 (3), and [Cu(2,2′‐bipy)(H2O)(IO3)2]· (H2O)2 (4) are hydrothermally synthesized at 120 °C for 6 d and characterized by single‐crystal X‐ray diffraction. The use of two different bidentate organodiamine ligands 1,10‐phen and 2,2′‐bipy in the V/I/O system gives rise to compounds 1 and 2, which crystallize in a monoclinic system with the space group C2/c, a = 17.8131(6) Å, b = 15.0470(7) Å, c = 12.9902(4) Å, β = 133.095(2)°, V = 2542.49(17) Å3 for 1 and space group P21/c, a = 13.3095(5) Å, b = 15.0993(8) Å, c = 13.0454(4) Å, β = 116.971(2)°, V = 2335.88(17) Å3 for 2. The use of the bidentate organodiamine ligand 2,2′‐bipy in the Cu/I/O system gives rise to the variety in the structure of products 3 and 4, which crystallize in a triclinic system with the same space group $P{\bar 1}$. a = 8.5143(2) Å, b = 10.4908(3) Å, c = 22.8420(6) Å, α = 93.769(10)°, β = 91.723(10)°, γ = 112.111(10)°, V = 1882.83(9) Å3 for 3 and a = 6.731(6) Å, b = 10.110(4) Å, c = 12.899(6) Å, α = 106.00(5)°, β = 95.45(4)°, γ = 107.69(6)°, V = 788.4(9) Å3 for 4. The solid‐state structures of the compounds 1 and 2 have chains with repeat units of alternative corner sharing of [VO4N2] octahedra and [IO3] pyramids. Compound 3 is a chain containing [IO3] pyramids and [VO4N] square pyramids and compound 4 consists of Cu(2,2′‐bipy)2+ linked by one water molecule and two [IO3] pyramids. The thermal stabilities of the compounds are investigated.
Synthesis, Structure, Spectral and Magnetic Properties of 1D Zig‐zag Coordination Complex: {[Ni(cyclam)(μ‐1,5‐dca)]ClO4·[(CH3)2CO]}n
Authors: Liu Hui , Tian Jin‐Lei , Kou Ying‐Ying , Gu Wen , Feng Li , Yan Shi‐Ping , Liao Dai‐Zheng
Published: June 2008

A new nickel(II) complex, {[Ni(cyclam)(μ‐1,5‐dca)]ClO4·[(CH3)2CO]}n (1), (cyclam = 1, 4, 8, 11‐tetraazacyclotetradecane, dca = dicyanamide, N(CN)2−) has been synthesized and structurally characterized. The complex crystallizes in orthorhombic system, space group Pnma; with a = 9.1958(15) Å, b = 15.528(3) Å, c = 16.335(3) Å and Z = 4. According to X‐ray crystallographic studies, 1 is a one‐dimensional zig‐zag infinite chain complex which consists of alternately single μ‐1,5‐dca linked the nickel atoms. The IR and UV spectroscopy were measured. The absorption bands of d–d electron transition are assigned and the values of Dq and B were calculated according to the electronic spectrum of the complex. The magnetic property studies indicate that complex 1 exhibits weak antiferromagnetic interaction through the five‐atom [NCNCN] bridging ligands with J = –0.382 cm−1.
Structural and NMR Studies of the Hexameric Copper(I) Complex with N‐n‐butyl‐N′‐ethoxycarbonyl‐thioureate
Authors: Boyd Sue E. , Healy Peter C. , Hope Gregory A. , Woods Ronald
Published: June 2008

The copper sulfide mineral flotation collector, N‐n‐butyl‐N′‐ethoxycarbonyl‐thiourea (H2bectu), and the 1:1 hexameric copper(I) thioureate complex, [Cu(Hbectu)]6, have been characterized by single crystal X‐ray diffraction. H2bectu crystallizes in the triclinic space group $\rm P{\bar 1}$ with a = 5.2754(4), b = 9.0042(7), c = 12.6030(9) Å, α = 80.528(6), β = 90.173(6), γ = 76.472(7)°. An intramolecular N‐H···O hydrogen bond between the thioamide proton and carbonyl oxygen forms a planar six‐membered ring in the central core of the molecule with C=O, C=S and C‐N bond lengths in accord with those reported for other N‐alkyl/aryl‐N′‐acyl‐thiourea compounds. [Cu(Hbectu)]6 crystallizes in the monoclinic space group C2/c with a = 23.269(5), b = 13.243(4), c = 23.037(7) Å, β = 91.81(2)° as discrete hexameric clusters disposed about a crystallographic centre of symmetry with a Cu6S6 core consisting of two Cu3S3 chair‐shaped rings linked by coordination of the deprotonated amide nitrogen atom to a copper atom in the adjacent ring. The six ligands assemble as a paddlewheel structure with the ethoxy and n‐butyl substituents packing in an alternating head to tail arrangement. Temperature dependent solution 1H NMR spectroscopic studies show that the hexameric structure of the complex is maintained in solution.
Zur Elektronenstruktur metallorganischer Komplexe der f‐Elemente. 68 Absorptions‐ sowie erstmalige lumineszenz‐ und Raman‐spektroskopische Polarisationsmessungen an einem orientierten metallorganischen Einkristall: Pr(C5Me4H)3
Authors: Amberger Hanns‐Dieter , Reddmann Hauke
Published: June 2008

Electronic Structures of Organometallic Complexes of f Elements. 68 Absorption and First Luminescence and Raman Spectroscopic Polarization Measurements of an Oriented Organometallic Single Crystal: Pr(C5Me4H)3

Optical polarization measurements of oriented single crystals of Pr(C5Me4H)3(1) were performed at room temperature. In order to separate “cold” and “hot” f‐f‐transitions and νC–H combination vibrations, the absorption spectra of KBr pellets of compound1and La(C5Me4H)3(2) were additionally recorded at ca. 77 K. To gather additional information about the wavefunctions of the crystal field (CF) states of complex1, a magnetic circular dichroism spectrum of1was recorded too. From the spectra obtained, a partial CF splitting pattern of1was derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian, leading to a reduced r.m.s. deviation of 24.8 cm−1for 24 assignments. On the basis of these phenomenological CF parameters, the global CF strength experienced by the Pr3+central ion was estimated, and seems to be the largest one ever encountered in PrIIIchemistry. The obtained Slater parameter F2and the spin‐orbit coupling parameter ζ4fallow the insertion of compound1into empirical nephelauxetic and relativistic nephelauxetic series, respectively, of PrIIIcompounds. With its low F2value, complex1is the most covalent PrIIIcompound (considering only f electrons) found to date. The experimentally‐based non‐relativistic molecular orbital scheme (in the f range) of complex1was determined and compared with the results of a previous Xα‐SW calculation on the ψ trigonal planar model compound Pr(η5‐C5H5)3. In the framework of the search for “polarized” luminescence transitions, polarized Raman spectra of1were recorded too, and compared to the corresponding FIR and IR spectra run by means of pellets.
Zinc Hydrazides and Hydrazide‐Alkoxides with Cyclic and Acyclic Hydrazide Substituents
Authors: Jana Surajit , Fröhlich Roland , Mitzel Norbert W.
Published: June 2008

The tetrameric organometallic zinc hydrazides the {(RZn)4[NHN(CH2)n]4} (R = Me, Et, iPr and n = 5, 4) (1–6), were prepared by alkane elimination from dialkyl zinc solutions and the ring‐substituted hydrazine derivatives 1‐aminopiperidine and 1‐aminopyrrolidine at ambient temperature. They were characterized by NMR (1H, 13C) and IR spectroscopy, by mass spectrometry and by elemental analyses. The compounds form asymmetric aggregates, containing Zn4N8 cores. Zinc trisalkoxide‐monohydrazides can be prepared in one‐pot syntheses by reacting dialkylzinc solutions simultaneously with alcohols and hydrazines. Reactions of dimethylzinc with isopropanol and monomethylhydrazine or mono‐t‐butylhydrazine in 2:1:1.03 ratio resulted in the formation of [(MeZn)4(NHNHR)(OiPr)3] [R = Me (7), tBu (8)]. In a similar fashion, dialkylzinc compounds react with 1‐aminopiperidine and alcohol in 5:4:4 ratio to give {(RZn)4[NHN(CH2)5](OR′)3]} [R = Me, R′ = iPr (9); R = Et, R′ = Et (10), iPr (11)]. These compounds were characterized as the above compounds. The structures of compounds 8 and 9 were also determined by crystal structure analyses. These compounds show an unsymmetrical aggregation with a Zn4N2O3 cage structure, confirmed by spectroscopic methods in solution.
Two New Quaternary Thiophosphates with Pseudo One‐dimensional Structures: Syntheses and Crystal Structures of Cs3Sm[PS4]2 and Rb3Sm[PS4]2
Authors: Milot Susanne , Wu Yuandong , Näther Christian , Bensch Wolfgang , Klepp Kurt O.
Published: June 2008

The new thiophosphates Rb3Sm[PS4]2 and Cs3Sm[PS4]2 were obtained as pale yellow needles using an in‐situ formed thiophosphate flux. Rb3Sm[PS4]2 crystallizes in the space group P21 with a = 9.7061(19) Å, b = 6.7517(14) Å, c = 11.395(2) Å, β = 90.63(3)°, (Z = 2); Cs3Sm[PS4]2 in space group P21/n with a = 15.311(3) Å, b = 6.8762(14) Å, c = 15.352(3) Å, β = 99.49(3)°, (Z = 4). The crystal structures are characterized by the formation of complex anionic chains, $^{1}_{\infty}\rm \{(Sm[PS_{4}]_{2})^{3-}\}$ which run along the [010] direction in both structures. One of the two independent thiophosphate groups connects three Sm3+ cations to form an infinite zigzag like arrangement, while the other acts as a terminal ligand to one Sm3+ions. Such a μ3 or face‐grafting coordination mode of a [PS4]3− anion is not very common. The Sm3+ ions are in bicapped trigonal prismatic chalcogen coordination. The average Sm–S distances within the trigonal prisms are close to 2.88Å, while the bonds to the capping atoms are distinctly longer. The chains are chiral yet their symmetry is close to 21/m. In contrast to the rubidium compound, Cs3Sm[PS4]2 contains both enantiomorphs. In both structures the chains are arranged as a distorted hexagonal rod packing.
Consistent‐inconsistent decomposition to initial value problem of descriptor linear systems
Authors: Yan Z.
Published: June 2008

Consistent‐inconsistent decomposition to initial value problem of descriptor linear systems is proposed. In this way the impulse part in the system response is clearly separated from the smooth part, and the phenomenon that inconsistency causes impulse is interpreted more perfectly. The decomposition is discussed also for time‐varying case.
Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway
Authors: Pajunen Taina I. , Johansson Mikael P. , Hase Tapio , Hopia Anu
Published: June 2008

Autoxidation of conjugated linoleic acid (CLA) methyl ester follows at least partly Farmer's hydroperoxide theory. A mechanism for this hydroperoxide pathway has been proposed based on autoxidation of 9‐cis,11‐trans‐CLA methyl ester. This investigation aims at confirming and further clarifying the mechanism by analyzing the hydroperoxides produced from 10‐trans,12‐cis‐CLA methyl ester and by theoretical calculations. Five methyl hydroxyoctadecadienoates were isolated by HPLC and characterized by UV, GC‐MS, and 1D‐ and 2D‐NMR techniques. In addition, an HPLC method for the separation of the intact hydroperoxides was developed. The autoxidation of 10‐trans,12‐cis‐CLA methyl ester in the presence of high amount of α‐tocopherol (20%) was diastereoselective in favor of one geometric isomer, namely Me 9‐OOH‐10t,12c, and produced new positional isomers 10‐ and 14‐hydroperoxides (Me 10‐OOH‐11t,13t; Me 14‐OOH‐10t,12c; and Me 14‐OOH‐10t,12t). Importantly, one of these new isomers, which was characterized as an intact hydroperoxide, had an unusual cis,trans geometry where the cis double bond is adjacent to the hydroperoxyl‐bearing methine carbon. Further insight to the mechanism was provided by calculating the relative energies for different conformations of the precursor lipid, the allylic carbon–hydrogen bond dissociation enthalpies, and the spin distributions on the intermediate pentadienyl radicals. As a result, a better understanding of the isomeric distribution of the product hydroperoxides was achieved and a modified mechanism that accounts for these calculations is presented.
Accuracy of a heart failure diagnosis in administrative registers
Authors: Kümler Thomas , Gislason Gunnar Hilmar , Kirk Vibeke , Bay Morten , Nielsen Olav W. , Køber Lars , Torp‐Pedersen Christian
Published: June 2008

Background:

The incidence of heart failure is frequently reported using hospital discharge diagnoses. The specificity of a diagnosis has been shown to be high but the sensitivity of a reported diagnosis is unknown.

Purpose:

To study the accuracy of a heart failure diagnosis reported to the Danish National Patient Registers during routine clinical work.

Methods:

The patient population consisted of 3644 consecutive patients admitted to all departments in one hospital. Diagnoses reported to the National Patient Register were recorded. A study team evaluated each patient independently of routine care, performed an echocardiogram and evaluated whether clinical symptoms of heart failure were present. Heart failure was defined in accordance with current ESC guidelines as symptoms of heart failure and evidence of cardiac dysfunction.

Results:

A registered diagnosis of heart failure (n=126) carried a specificity of 99% and a sensitivity of 29% for all patients. The positive predictive value was 81%, the negative predictive value 90%.

Conclusion:

The diagnosis of Heart Failure in the Danish National Registers is underreported, but very specific.
Neuroimaging studies of the early stages of psychosis: A critical review
Authors: Fusar-Poli Paolo , Allen Paul , McGuire Philip
Published: June 2008

Psychiatric imaging, in particular functional imaging techniques such as functional magnetic resonance imaging (fMRI) are potentially powerful tools to explore the neurophysiological basis of the early stages of psychosis. Despite this impressive growth, neuroimaging has yet to become an established as diagnostic instrument this area, partly as a result of significant heterogeneity across the findings from research studies. The present review aims to: (i) assess the determinants of inconsistencies in the results from neuroimaging studies of the early stages of psychosis; and (ii) suggest approaches for future imaging research in this field that may reduce methodological differences between studies.
Tomatidine inhibits iNOS and COX‐2 through suppression of NF‐κB and JNK pathways in LPS‐stimulated mouse macrophages
Authors: Chiu Feng-Lan , Lin Jen-Kun
Published: June 2008

We use the LPS‐stimulated macrophage as a model of inflammation to investigate the anti‐inflammatory effects of tomatidine and solasodine, whose structures resemble glucocorticoids. We found that tomatidine exhibited a more potent anti‐inflammatory effect than solasodine. Tomatidine could decrease inducible nitric oxide synthase and cyclooxygenase‐2 expression through suppression of I‐κBα phosphorylation, NF‐κB nuclear translocation and JNK activation, which in turn inhibits c‐jun phosphorylation and Oct‐2 expression. Here, we demonstrate that tomatidine acts as an anti‐inflammatory agent by blocking NF‐κB and JNK signaling, and may possibly be developed as a useful agent for the chemoprevention of cancer or inflammatory diseases.
Regulation of SIRT1 protein levels by nutrient availability
Authors: Kanfi Yariv , Peshti Victoria , Gozlan Yosi M. , Rathaus Moran , Gil Reuven , Cohen Haim Y.
Published: June 2008

The mammalian NAD+ dependent deacetylase, SIRT1, was shown to be a key protein in regulating glucose homeostasis, and was implicated in the response to calorie restriction. We show here that levels of SIRT1 increased in response to nutrient deprivation in cultured cells, and in multiple tissues of mice after fasting. The increase in SIRT1 levels was due to stabilization of SIRT1 protein, and not an increase in SIRT1 mRNA. In addition, p53 negatively regulated SIRT1 levels under normal growth conditions and is also required for the elevation of SIRT1 under limited nutrient conditions. These results have important implications on the relationship between sirtuins, nutrient availability and aging.
Spliceosomal immunophilins
Authors: Mesa Annia , Somarelli Jason A. , Herrera Rene J.
Published: June 2008

The spliceosome is a dynamic, macromolecular complex, which removes non‐protein‐coding introns from pre‐mRNA to form mature mRNA in a process known as splicing. This ribonucleoprotein assembly is comprised of five uridine‐rich small nuclear RNAs (snRNAs) as well as over 300 proteins. In humans, several of the known proteinaceous splicing factors are members of the immunophilin superfamily. Immunophilins are peptidyl‐prolyl cis–trans isomerases that catalyze the conversion of proteins from cis to trans at Xaa‐Pro bonds. Our review of the data indicates that some members of this protein family are activators of spliceosomal proteins by way of folding and transport.
APPROXIMATION BY SEVERAL RATIONALS
Authors: SHPARLINSKI IGOR E.
Published: June 2008

Following T. H. Chan, we consider the problem of approximation of a given rational fraction a/q by sums of several rational fractions a1/q1,…,an/qn with smaller denominators. We show that in the special cases of n=3 and n=4 and certain admissible ranges for the denominators q1,…,qn, one can improve a result of T. H. Chan by using a different approach.
Accidents and opportunities: a history of the radio echo-sounding of Antarctica, 1958–79
Authors: TURCHETTI SIMONE , DEAN KATRINA , NAYLOR SIMON , SIEGERT MARTIN
Published: June 2008

This paper explores the history of radio echo-sounding (RES), a technique of glaciological surveying that from the late 1960s has been used to examine Antarctica's sub-glacial morphology. Although the origins of RES can be traced back to two accidental findings, its development relied upon the establishment of new geopolitical conditions, which in the 1960s typified Antarctica as a continent devoted to scientific exploration. These conditions extended the influence of prominent glaciologists promoting RES and helped them gather sufficient support to test its efficiency. The organization and implementation of a large-scale research programme of RES in Antarctica followed these developments. The paper also examines the deployment of RES in Antarctic explorations, showing that its completion depended on the availability of technological systems of which RES was an integral part.
Molecular and morphological evidence for the occurrence of Anisakis sp. A (Nematoda, Anisakidae) in the Blainville's beaked whale Mesoplodon densirostris
Authors: Iglesias R. , D'Amelio S. , Ingrosso S. , Farjallah S. , Martínez-Cedeira J.A. , García-Estévez J.M.
Published: June 2008

Twenty-three adults (only one male) and two fourth-stage larvae of Anisakis, recovered from the stomach of a Blainville's beaked whale (Mesoplodon densirostris) stranded in Galicia (NW Spain), were studied morphologically and molecularly. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequencing studies carried out on the ribosomal DNA spacers and on the cox2 mitochondrial gene confirm that these nematodes belong to the taxon Anisakis sp. A, which was previously detected as a larval stage in fishes from Madeiran waters. In addition, our molecular studies demonstrate that Anisakis sp. A and the taxon Anisakis sp., previously found in other Mesoplodon spp., are the same species. The adults of Anisakis sp. A are morphologically similar to A. ziphidarum but with a shorter body length and longer spicules (right spicule 2.42 mm, left spicule 2.30 mm). Since the poor condition of the male tail cuticle prevented a proper description of the caudal plates and the pattern of caudal papillae, we propose to retain the name Anisakis sp. A until new males are described correctly.
Single dose injection snoreplasty: investigation or treatment?
Authors: Al-Jassim A H , Lesser T H J
Published: June 2008

Introduction:

Many surgical and nonsurgical procedures have been designed for the treatment of snoring due to palatal flutter. All work in some, but not all, snorers. The difficulty lies in making the definitive diagnosis of palatal flutter as the cause of snoring, and in deciding which patients should undergo which treatment, which in some cases are relatively radical.

Aims:

This study aimed to assess the usefulness of injection snoreplasty in differentiating palatal flutter from other forms of snoring. This was done in the hope of determining which patients would benefit from definitive palatal surgery such as uvulopalatopharyngoplasty and laser-assisted uvuloplasty.

Materials:

Sixty consecutive patients referred for habitual snoring were treated with sodium tetradycil sulphate during their first consultation visit. No patients were excluded and none refused the treatment. Forty patients received a single 1 ml dose of 1 per cent sodium tetradycil sulphate, and twenty patients received a single 1 ml dose of 3 per cent sodium tetradycil sulphate under topical anaesthesia. Visual analogue snoring scales were completed by the patient and their partner six weeks, three months, six months and 12 months after the procedure.

Results:

Forty of the 60 patients showed improvement in snoring and therefore were considered for definitive surgery. Four of the 60 patients found the investigation unpleasant and did not want any further treatment. Of the 40 patients who showed improvement, 29 maintained this at one year. The other 11 underwent uvulopalatopharyngoplasty or laser-assisted palatoplasty. All patients had successful snoring scale outcomes following the surgery.

Conclusion:

A significant number of the patients, 62 per cent, were demonstrated to have significant improvement in the short term. Single dose injection snoreplasty seems not only to be an effective investigation but may constitute a safe and simple treatment within the clinic. At the very least, patients in whom the palate appears not to be the problem are prevented from undergoing painful, unpleasant surgery. Our results support the use of injection snoreplasty, both as an investigation and in some patients as a treatment, for habitual snoring.
On Faithfulness: The Difficulties Experienced by the Text/Performance Couple
Authors: PAVIS PATRICE
Published: June 2008

The question of whether the director has been faithful to the author or whether the production conforms to the text of the play resurfaces in many different shapes. Three recent theories are given as examples of this dogma of necessary fidelity. But this dualism is itself historically relativistic. Examples of recent productions show that the text–performance ‘couple’ must constantly be reconsidered.