bluuebunny/crossref_metadata_2025 huggingface dataset:
Anregung und Messung von Eigenschwingungen zur Beurteilung der Bettungsbedingungen von erdverlegten Abwasserrohren (Assessing the Bedding Conditions of Sewer Pipes using Eigenvibration)
Authors: Herbst Jürgen
Published: December 2003

Ein akustisches Sensorsystem, das Rohrimpactometer, wird eingesetzt, um eine Integritätsprüfung an Abwasserrohren durchzuführen. Hierbei wird die Rohrwand impulsförmig angeregt. Die sich im Rohr allseitig ausbreitenden Schwingungen werden mit Beschleunigungssensoren erfasst und geben Aufschluss über den Zustand des geprüften Rohrabschnittes hinsichtlich der Bettungsbedingungen bzw. das Rohrumfeld.
Neuro-Fuzzy basierte Sensorfusion zur qualifizierten Schadensdiagnose an Abwasserkanälen (Neuro-Fuzzy Based Multisensor Diagnosis Concept for Qualified Condition Assessment in Sewer Systems)
Authors: Frey Christian W. , Kuntze Helge-Björn
Published: December 2003

Eine umfassendere qualifizierte Schadensdiagnose in kommunalen Kanalsystemen ist nur dann möglich, wenn die vorhandene TV-Technik durch eine objektiv messende multisensorielle Schadensdiagnose ergänzt wird. In dem von der deutschen Forschungsgesellschaft DFG geförderten Forschungsverbundvorhaben SAM wurden alternative Inspektionssensoren entwickelt und hinsichtlich ihrer Leistungsfähigkeit untersucht. Zur Integration der komplementären Sensorinformation zu einem ganzheitlichen Schadensbild wurde ein Neuro-Fuzzy basiertes multisensorielles Diagnosekonzept entwickelt und erprobt, über das in diesem Beitrag berichtet wird.
Gemeinsame Testeinrichtungen der SAM-Forschergruppe (Experimental Test Facilities of the SAM Research Group)
Authors: Eiswirth Matthias
Published: December 2003

Die Partner der DFG-Forschergruppe 〟Schadensdiagnose bei Abwasserkanälen mit Multisensorsystemen〞 (SAM) haben neben der Entwicklung von neuen Sensoren zur objektiven, quantitativen Erfassung von Kanalschäden auch versucht, eine zusätzliche Quantifizierung des Schadensausmaßes leisten. Nach der Weiterentwicklung und problemorientierten Adaption der ausgewählten Sensoren wurden Messungen zur Kalibrierung der innerhalb der Kanalrohre ermittelten Ergebnisse durch Untersuchungen außerhalb der Rohre in verschiedenen Testeinrichtungen im Labor und Gelände durchgeführt. Im Nachfolgenden werden diese Testeinrichtungen näher beschrieben.
Crystallisation of caesium borosilicate glasses with approximate boroleucite composition
Authors: Hübner R. , Belger A. , Meyer D. C. , Paufler P. , Polyakova I. G.
Published: December 2003

Crystallisation and annealing behaviour of two caesium borosilicate glass samples with approximate boroleucite composition were characterised by means of differential scanning calorimetry measurements as well as X-ray powder diffraction investigations with subsequent profile fitting of the observed patterns according to the Rietveld and/or Pawley method. While one sample crystallised primarily in an orthorhombic phase (a= 6.592(3) Å,b= 11.825(5) Å,c= 12.620(6) Å; possible space groups:Pmc21((26), setting:P21am),Pma2 (28) andPmma((51), setting:Pmam)) which has been unknown until now and transformed irreversibly into the well-known cubic boroleucite phase atT≈ 850 °C, cubic caesium boroleucite (space group:Ia3̅d(230)) was crystallised directly from the other sample. In this case, the orthorhombic phase was metastable. At the onset temperature of glass crystallisationTx, on= 770 °C, it existed only for about 75 min. The change of the lattice parameteraof the cubic unit cell of caesium boroleucite in the course of the thermal treatments was explained by the alteration of the size of the TO4tetrahedra (T = Si, B).
The crystal structure determination of the crystalline layered silicic acid H-RUB-18
Authors: Borowski M. , Marler B. , Gies H.
Published: December 2003

The layer silicate H-RUB-18 (chemical compo-sition: Si4O7(OH)2) was prepared by ion exchange from the parent material Na-RUB-18. The high degree of structural disorder typical for this material precluded a classical structure analysis based on diffraction data only. Nevertheless, a detailed picture of the structure was obtained by a step by step process using a combination of complementary methods: Crystal chemical considerations and solid state NMR spectroscopy allowed to establish a rough model of the structure which was optimized by forcefield molecular dynamics (MD) simulations. A subsequent Rietveld refinement in space group I41/amd confirmed the model consisting of a sequence of pseudo tetragonal silicate layers with an intra-layer repeat unit a = 7.38 Å and inter-layer distances of c = 7.44 Å. The main type and degree of disorder was analyzed by the simulation of various stacking sequences of rigid silicate layers which served as the building blocks. The random displacement of consecutive layers is accompanied by a slight distortion of the layers as indicated by an additional density functional theory (DFT) energy minimization calculation in triclinic symmetry. The given displacement and distortion allow for the formation of hydrogen bonds between the terminal OH groups necessary for the stabilization of the structure. The concept of a structure analysis presented in this paper may be suitable as a guide line to be applied to many other disordered materials.
Characterization of the stuffed framework structures BaAlGaO4 and BaFeGaO4
Authors: Kahlenberg V. , Parise J. B. , Lee Y. , Tripathi A.
Published: December 2003

The crystal structures of the compounds BaMGaO4 (M = Al, Fe) have been investigated using conventional single-crystal X-ray diffraction data for M = Fe and with synchrotron radiation data for M = Al. BaAlGaO4 (space group P6322, a = 5.2788(4) Å and c = 8.7835(7) Å, V = 211.97(4) Å3, Z = 2, D
calc. = 4.67 g cm–3, wR2 = 0.089 for 242 independent reflections with I > 2σ(I)) is isostructural with BaAl2O4-I. Main building units are layers of six-membered rings of (Al,Ga)O4-tetrahedra perpendicular to [001]. The sequence of directedness of the tetrahedral apices in all single six membered rings (S6R) is UDUDUD (U: up, D: down). Stacking of layers parallel to c results in a three-dimensional framework containing tunnels, where the Ba atoms are located. They are coordinated by nine oxygen ligands in form of distorted tricapped trigonal antiprisms. BaFeGaO4 also belongs to the hexagonal crystal system (space group P63, a = 10.8377(6) Å and c = 8.6865(6) Å, V = 883.59(9) Å3, Z = 8, D
calc. = 4.92 g cm–3, wR2 = 0.099 for 1042 independent observed reflections). The crystal showed twinning by merohedry which was accounted for in the refinement calculations. Within a single tetrahedral layer of the framework structure two different types of ditrigonal-shaped rings are distinguishable: one fourth of the rings have an UDUDUD topology, whereas the sequence of the remaining rings is UUUDDD. The Fe3+- and Ga3+-cations show an ordered distribution among the four symmetrically independent T-sites: two positions contain either Fe or Ga, whereas on the remaining two sites there is a definite preference for one of the two cation species. The Ba atoms in the cavities of the framework are coordinated by eight to nine oxygen neighbors. The observed twinning in BaFeGaO4 can be attributed to the existence of pseudo twofold axis within the tetrahedral layers, running parallel [100] and the corresponding symmetrically equivalent directions.
Isotypism and low-dimensional physical properties of CuAs2/3H2/3O3 (theoparacelsite), the spin-Peierls phase CuGeO3 and CuSiO3
Authors: Otto H. H. , Wolfram H.
Published: December 2003

Theoparacelsite is a recently discovered orthorhombic copper arsenate hydroxide mineral with the ideal chemical formula Cu3As2O7(OH)2, but because of disorder only two smaller formula units CuAs2/3H2/3O3 are established in the orthorhombic unit cell with lattice parameters a = 4.6644(5) Å, b = 8.3212(8) Å and c = 2.9377(3) Å, and space group Pbmm. We show that this rare mineral is iso-typic to the unique inorganic spin-Peierls phase CuGeO3 (TSP
= 14.3 K) and to the recently discovered copper polysilicate, CuSiO3, which is also a quasi-one-dimensional S = 1/2 anti-ferromagnetic chain compound (TN
= 7.9 K). We discuss in detail the previously reported crystallographic data of the phases at room temperature in view of its ability to attain similar low-dimensional physical properties and conclude that the arsenate with its S = 1/2 spin chains of edge-sharing CuO4+2 octahedra may be a further inorganic compound that could show the spin-Peierls effect. Although the Cu-O(2)-Cu angle, which is considered to be important for the magnetic interaction and ground state properties, has been found for the arsenate (98.8°) almost identical to that of the germanate (99.1°), the modified inter-chain coupling of the arsenate as a defect variant of the CuGeO3 structure type may suppress the spin-Peierls effect and favour other states of magnetic order (chiral spin chains, AF order). With respect to the rarity of the mineral some remarks on synthesis routes are made.
Natural and synthetic compounds with kröhnkite-type chains: review and classification
Authors: Fleck Michel , Kolitsch U. , Hertweck B.
Published: December 2003

The crystal structure of kröhnkite [Na2Cu(SO4)2·2H2O], which contains infinite chains composed of CuO6 octahedra corner-linked with SO4 tetrahedra, was originally determined 1952 by Dahlman. Since then, a large number of both minerals (e.g., collinsite, fairfieldite, etc.) and synthetic compounds with closely related struc-tures have been investigated, but the structural relation was not always recognised. In the present review we compare the structures of AnM(XO4)2·2H2O (A = mono- or divalent cation, n = 1, 2; M = di- or trivalent cation; X = penta- or hexavalent cation) compounds with kröhnkite-type infinite chains, and propose a structural classification into six types. The rod group symmetries of the chains are compared. Furthermore, the linkage of these chains to double chains (in krausite-type compounds) and sheets (in yavapaiite-, merwinite-, bafertisite-type and similar structures) is discussed, and the occurrence of octahedral-tetrahedral chains topologically identical to those in kröhnkite (referred to as kröhnkite-type) and similar chains (referred to as kröhnkite-like) in several related compounds is pointed out.
Thermal behaviour of the rigid boron-oxygen groups in the α-Na2B8O13 crystal structure
Authors: Bubnova R. S. , Shepelev Ju. F. , Sennova N. A. , Filatov S. K.
Published: December 2003

The crystal structure of the α-Na2B8O13 stable modification has been refined by single crystal X-ray diffraction at 293, 573 and 773 K. The compound is monoclinic, P21/a space group, unit-cell parameters at 273 K are: a=6.507(3), b=17.796(8), c=8.377(5) Å, β=96.60(4)°, Z=4. The structure contains two interlocking boron-oxygen frameworks, each of them consisting of alternating single and double rings composed of two triangles and a tetrahedron so called triborate and pentaborate groups. Two non-equivalent sodium atoms linking two frameworks are coordinated by 8 oxygens. They are connected into finite chains consisting of four NaO8 polyhedra by sharing oxygen edges. The α-Na2B8O13 thermal expansion investigated by high temperature powder X-ray diffraction has sharply anisotropic character including negative thermal expansion: the coefficients of a thermal expansion tensor in temperature region 273–1000 K are α11 = 55–0.042·(273+t), α22 = 11, α33 = -15 + 0.032·(273+t) (×10–6 K–1), μ = (c^α33) = 42°. That high anisotropy is caused by anisotropic thermal vibrations of the Na atoms. Under heating a high stability of the B-O rigid groups and a weak contraction of some B-O bond lengths were revealed. In response to anisotropic thermal behaviour of Na atoms rigid B-O groups of the anion framework rotate relative to each other as a three-dimensional hinge.
Crystal structure of Pb10O7(OH)2F2(SO4) and crystal chemistry of lead oxysulfate minerals and inorganic compounds
Authors: Krivovichev Sergey V. , Burns Peter C.
Published: December 2003

The crystal structure of Pb10O7(OH)2F2(SO4) (triclinic, P1̅, a = 9.6637(16), b = 10.1922(17), c = 11.1407(18) Å, α = 110.978(3), β = 91.795(3), γ = 107.020(3)°, V = 968.2(3) Å3) has been solved by direct methods and refined to R1 = 0.050 (wR = 0.089). There are ten symmetrically unique Pb2+ cations in the structure all of which have highly asymmetric coordination polyhedra owing to presence of stereoactive 6s
2 lone pairs of electrons. The structure is based upon [O7Pb10] zigzag chains of edge-sharing OPb4 oxocentered tetrahedra. The observed [O7Pb10] chain is the most complex chain of oxocentered tetrahedra known so far and was not observed previously in structures of inorganic compounds. The chains run along [011] and their plane is parallel to (111). The chains form sheets parallel to (111). The SO4) tetrahedra, F– anions and OH groups are between the sheets providing their linkage into three-dimensional structure. A comparison of the structure with other Pb oxysulfates is given in the framework of theory of complexes of anion-centered tetrahedra.
Lattice parameters of La3Ga5SiO14 as a function of hydrostatic pressure
Authors: Werner S. , Maximov B. , Schulz H. , Molchanov V. , Vigdorchik A. , Pisarevskii Yu.
Published: December 2003

Langasite (La3Ga5SiO14) crystallizes in the polar space group P321. Here we report the pressure dependence of the lattice parameters at high hydrostatic pressures up to 10.2 GPa. The results presented in terms of compressibility agree well with results from measurements of the elastic constants. According to a Birch-Murnaghan equation of state, the bulk modulus and its pressure derivative are 134.6(2) and 2.8(1) GPa, respectively. The compression of langasite crystals is anisotropic, the c/a-ratio appears to be a linear function of the pressure applied according to c/a = 0.62460(6) + 0.00055(1)* p/GPa. Altogether four single crystals have been investigated. Two of them showed a splitting of reflections (hhl). This splitting reaches a maximum at approximately 9 GPa and proved to be reversible.
Comparative topological analysis of simple anhydrous borates, carbonates and nitrates
Authors: Blatov V. A. , Zakutkin Yu A.
Published: December 2003

Topological analysis and comparing of the crystal structures of anhydrous inorganic salts containing triangular oxo-anions (borates, carbonates and nitrates) was performed using the program package for multipurpose crystallochemical analysis TOPOS. The examples of topological similarities between these classes of substances and 2920 framework binary compounds AyXz were revealed and discussed. It is shown that in most cases the ionic arrays constructed according to one of close packings or to a b.c.c. motif can be selected in the crystal structures of anhydrous inorganic salts. The conclusions were made about the structure-forming role of atoms and atomic groups in these substances. The crystal structures of anhydrous salts are substantiated to be correctly considered as packings of metal cations and quasi-spherical oxo-anions.
Crystal structures and phase transitions of (NO)2TiCl6
Authors: Henke Henning
Published: December 2003

Solid (NO)2TiCl6 undergoes two phase transitions closely related to the order-disorder behaviour of the NO+ species present in this salt-like compound. Starting from ambient conditions the sequence of space groups is P4/mnc → C2/c → P21/n when the temperature is lowered. At Tc

1 = 199 K the formation of quadruplet domains is observed, while at Tc

2 = 176 K superstructure reflexions appear due to decentring of the unit cell. In the tetragonal high-temperature form the orientational disorder of the nitrosonium groups is fourfold, partial order then starts to develop in the intermediate phase, whereas almost complete order is reached at 123 K in the second monoclinic phase. This two-step symmetry reduction was studied by DSC, powder diffraction, and by single-crystal measurements including complete structure determinations at 291, 203 and 123 K. In P21/n the selection of just one NO+ orientation per site is coupled to a characteristic displacement pattern of the titanium atoms. For electrostatic reasons the latter show a response to short N···Cl contacts by an off-centre shift (ca. 11pm) inside their 'octahedral' chlorine cages. The stereochemical influence of antibonding NO+ orbitals determines the inclination of the cation towards the nearest chlorine neighbours.
A structural study of polymorphism in phenyl salicylate: determination of the crystal structure of a meta-stable phase from X-ray powder diffraction data using a direct space systematic search method
Authors: Hammond R. B. , Jones M. J. , Roberts K. J. , Kutzke H. , Klapper H.
Published: December 2003

In this paper we report the crystal structure solution of a meta-stable phase of phenyl salicylate (salol). This modification, which is obtained from a super-cooled melt, has been observed before, but the structure has not been previously determined. Structure solution was achieved by a procedure combining a computer based systematic search method with a subsequent Rietveld refinement of experimental X-ray powder diffraction data. A clustering procedure to group similar trial structures based upon energy minimisations is discussed. The best trial structure identified by the combination of a systematic search and clustering was refined using the Rietveld method and a final structure with a weighted pattern indexRwpof 0.0513 (excluding background) was obtained. The meta-stable phase of salol crystallises with a monoclinic unit cell with cell parametersa= 17.4047(8) Å,b= 5.9800(5) Å,c= 10.6882(7) Å, and β = 108.988(5)º. The space group isP21/nwith four molecules in the unit cell. A structural comparison of the stable and meta-stable modifications is given.
A new case of polymorphism in platinum(II) complexes: [PtBr2(2,9-dimethyl-1,10-phenanthroline)]
Authors: Capitelli F. , Margiotta N. , Moliterni A. G. G. , Natile G.
Published: December 2003

A novel case of polymorphism in platinum(II) complexes is reported. Single crystals of [PtBr2(2,9-dimethyl-1,10-phenanthroline)] were obtained at room temperature from a dilute dichloromethane/pentane (1:3, v/v) solution of the title compound in the presence of guanosine. The space group resulted to be Pbca [a = 20.4024(3), b = 20.3638(3), and c = 13.9522(2) Å, V = 5796.7(1) Å3, Z = 8]. Crystals of the same compound, obtained in slightly different conditions, had already been investigated by X-ray diffraction and found to have P21/n space group, [a = 12.155(4), b = 7.933(2), and c = 14.522(2) Å, β = 93.74(2)°, V = 1397.3(6) Å3, Z = 4]. Comparison of the two polymorphous forms reveals huge differences in the crystal packing and the important role of the stacking interactions between phenanthroline ligands.
The Absorption Spectrum of C4
Authors: Jungen M. , Xu R.
Published: December 2003

New quantum chemical calculations for the optical valence transitions of C4 have been carried out for both vertical excitation energies up to 6 eV and oscillator strengths. For some of the transitions, including the only one predicted to be in the visible spectrum, we found strong dependence of the transition moment on the molecular geometry, leading to inaccurate predictions for the transition probabilities if a local value is used instead of an appropriate average. It is proposed to calibrate the absorbance of C4 using an electronic excitation in the near infrared.
Analysis of the Quality of Kohn–Sham Orbitals for Subsequent MRSD-CI Calculations of Excitation Energies
Authors: Hupp T. , Engels B. , Della Sala F. , Görling A.
Published: December 2003

In the present work we study the properties of Kohn–Sham orbitals used in subsequent CI methods for the computation of electronic excitation energies in terms of orbital relaxation, static and dynamical correlation effects. As model systems, we use the water and the ethene molecule. As sets of orbitals, we use orbitals from an effective exact exchange Kohn–Sham method, the localized Hartree–Fock (LHF) method, as well as BLYP and HF orbitals. Our study shows that the use of LHF orbitals leads to negligible static correlation effects and thus facilitates assignments of excitation spectra, but it also shows that the remaining correlation contributions have to be taken into account carefully since error cancellation is only found in some fortitious cases. The comparison of LHF and BLYP orbitals shows that the BLYP orbitals are less suited for the description of the cationic system and as a consequence for the computation of Rydberg states.
Linear Centrosymmetric SiC5Si: Floppy or Not?
Authors: Botschwina P.
Published: December 2003

Linear SiC5Si has been studied by the coupled cluster variant CCSD(T) and a large basis set of 393 contracted Gaussian-type orbitals. The full cubic force field was calculated, from which a variety of spectroscopic constants was obtained. The calculations indicate that linear SiC5Si behaves like a fairly normal semirigid molecule. In particular, excitation of any of its vibrations by one vibrational quantum leads to changes in the rotational constant not exceeding 0.3%.
Quantum Chemical Calculation of Raman Intensities for Large Molecules: The Photoisomerization of [{Fe‘S4’(PR3)}2(N2H2)] (‘S4’2− = 1,2-bis(2-Mercaptophenylthio)-Ethane(2−))
Authors: Reiher M. , Neugebauer J. , Hess B. A.
Published: December 2003

Since Raman spectra of isolated large molecules are hardly accessible by present day quantum chemical methods, we demonstrate how Raman intensities for selected vibrational normal modes can be calculated by extension of a semi-numerical, very flexible approach to the calculation of vibrational spectra [see J. Neugebauer et al., J. Comp. Chem. 23 (2002) 895–910]. The methodology is applied to a Ci
-symmetric dinuclear diazene iron–sulfur complex with relevance to the biological nitrogen fixation problem. The accuracy of the vibrational spectra allows us to use the spectra for structure determination and assignment of bands to isomeric structures, which were conjectured to be generated by a photoisomerization process. We can in turn support the photoisomerization hypothesis.
Synthesis and Antibacterial Activity of 1β‐Methyl‐2‐(5‐substituted oxadiazolo pyrrolidin‐3‐yl‐thio)carbapenem Derivatives
Authors: Oh Chang‐Hyun , Dong Hyun‐Gu , Lee Joo‐Shin , Lee Su‐Chul , Hong Joon Hee , Cho Jung‐Hyuck
Published: December 2003

Synthesis of a new series of 1β‐methylcarbapenems with a substituted oxadiazolopyrrolidine moiety is described. Their in vitro antibacterial activities against both Gram‐positive and Gram‐negative bacteria were tested and the effect of the substituent on the oxadiazole ring investigated. In particular, compounds 13a and 13c with ester and carbamoyl substituted oxadiazole moieties showed the most potent antibacterial activity.
1, 2‐Dihydroisoquinoline‐N‐Acetic Acid Derivatives as New Carriers for Specific Brain Delivery I: Synthesis and Estimation of Oxidation Kinetics Using Multivariate Calibration Method
Authors: Mahmoud Sahar , Aboul‐Fadl Tarek , Sheha Mahmoud , Farag Hassan , Mouhamed Abdel‐Maaboud I.
Published: December 2003

In order to overcome the slow oxidation of 1, 2‐dihydro‐N‐alkylisoquinoline, 1, 2‐dihydroisoquinoline‐N‐acetic acid derivatives (3b—d) were designed and synthesized as new chemical delivery systems (CDS) for the brain. Molecular orbital calculations for the suggested derivatives revealed that these carriers are stable against oxidation. However, hydrolysis to their corresponding anions will accelerate the rate of oxidation, and accordingly increase the efficiency of brain specific delivery. A multivariate calibration method for in vitro determination of the oxidation rate for the suggested brain specific chemical delivery system is described. The method is based on measurement of individual rates of oxidation of prepared 1, 2‐dihydroisoquinolines, using silver ions to provide the corresponding quaternary forms. Components of binary mixtures formed through the oxidation step (composed of the dihydro‐compound and its quaternary form), showed a considerable degree of spectral overlapping — more than 90% in all cases. Resolution of these binary mixtures under investigation has been accomplished mainly using classical least squares analysis. Kinetic oxidation data of the tested compounds revealed that these new CDSs have a reasonable oxidation rate for efficient brain delivery.
The Low‐Lying Excited States of 2,2′‐Bithiophene: A Theoretical Analysis
Authors: Rubio Mercedes , Merchán Manuela , Pou‐Amérigo Rosendo , Ortí Enrique
Published: December 2003

The low‐energy regions of the singlet→singlet, singlet→triplet, and triplet→triplet electronic spectra of 2,2′‐bithiophene are studied using multiconfigurational second‐order perturbation theory (CASPT2) and extended atomic natural orbitals (ANO) basis sets. The computed vertical, adiabatic, and emission transition energies are in agreement with the available experimental data. The two lowest singlet excited states, 11Bu and 21Bu, are computed to be degenerate, a novel feature of the system to be borne in mind during the rationalization of its photophysics. As regards the observed high triplet quantum yield of the molecule, it is concluded that the triplet states 23Ag and 23Bu, separated about 0.4 eV from the two lowest singlet excited states, can be populated by intersystem crossing from nonplanar singlet states.
In‐Plane Structures of Synthetic Oligolactose Lipid Monolayers—Impact of Saccharide Chain Length
Authors: Tanaka Motomu , Schneider Matthias F. , Brezesinski Gerald
Published: December 2003

Grazing incidence X‐ray diffraction (GIXD) was used to investigate the in‐plane structure of monolayers of synthetic glycolipids with oligolactose head groups (Lac N, with N=number of lactose units) at the air/water interface. The Lac 1 monolayer exhibits three sharp diffraction peaks. One peak can be deconvoluted into two diffraction peaks, which suggests that alkyl chains in the monolayer form an orthorhombic lattice. On the other hand, the other two peaks are related to bulk crystalline materials residing at the interface. Another weak peak from the head group correlation, either in a monolayer or in bulk crystals, can also be observed in some experiments. The scattering patterns of the Lac 2 monolayer indicate that the alkyl chains order in an orthorhombic lattice, where a shift in the hydrophilic/hydrophobic balance seems to fluidize the film. Alkyl chains in the Lac 3 monolayer also seem to assume an orthorhombic lattice; however, a weak diffraction peak from the correlation between trilactose head groups can also be observed. The estimated lattice dimensions are compared systematically to those of bulk dispersions, as well as to the viscoelastic properties of the monolayer. The obtained results strongly suggest that the in‐plane structure of synthetic glycolipid monolayers can provide a well‐defined basis to understand the impact of the chemical structure on the cooperativity and function of the glycocalix of cellular surfaces.
Trends in Microfluidics with Complex Fluids
Authors: Pfohl Thomas , Mugele Frieder , Seemann Ralf , Herminghaus Stephan
Published: December 2003

The rapid developments in biotechnology create a great demand for fluid handling systems on the nano‐ and picoliter scale. The characterization of minute quantities of DNA or protein samples requires highly integrated, automated, and miniaturized “total analysis systems” (μ‐TAS). The small scales necessitate new concepts for devices both from a technological and from a fundamental physical point of view. Here, we describe recent trends in both areas. New technologies include soft lithography, chemical, and topographical structuring of surfaces in order to define pathways for liquids, as well as electrowetting for manipulation purposes. Fundamentally, the interplay between geometric confinement and the size of biological macromolecules gives rise to complex dynamic behavior. The combination of both fluorescence imaging and scattering techniques allows for detailed insight into the dynamics of individual molecules and into their self‐assembly into supramolecular aggregates.
Generation of Iron Atoms in the Gas Phase by Microwave‐Induced Plasma Afterglows
Authors: Vinckier Chris , Cappan Kevin
Published: December 2003

A fast‐flow reactor technique is described by which Fe atoms can be produced in the gas phase in the afterglow of microwave‐induced plasmas in hydrogen/argon and hydrogen/helium mixtures. When the iron salt FeCl3(s) was brought into the gas phase by thermal sublimation at temperatures between 360 and 405 K, it was partly converted to Fe atoms by reaction of the gaseous compounds FexCl3x(g) with hydrogen atoms. The Fe atoms were detected by atomic absorption spectroscopy (AAS). It was shown that sublimation of the salt is the rate‐determining step of the overall plasma‐afterglow atomisation process. Experimental conditions for the generation of Fe atoms suited to kinetic studies start at a temperature of 303 K. In the downstream region the concentration of Fe atoms decays due to diffusion to the reactor wall. Binary diffusion coefficients DFe/Ar and DFe/He of 231.5±6.6 and 370.0±15.5 cm2 s−1 Torr at 303 K, respectively, were determined.
Single‐Walled Carbon Nanotube Based Molecular Switch Tunnel Junctions
Authors: Diehl Michael R. , Steuerman David W. , Tseng Hsian‐Rong , Vignon Scott A. , Star Alexander , Celestre Paul C. , Stoddart J. Fraser , Heath James R.
Published: December 2003

This article describes two‐terminal molecular switch tunnel junctions (MSTJs) which incorporate a semiconducting, single‐walled carbon nanotube (SWNT) as the bottom electrode. The nanotube interacts noncovalently with a monolayer of bistable, nondegenerate [2]catenane tetracations, self‐organized by their supporting amphiphilic dimyristoylphosphatidyl anions which shield the mechanically switchable tetracations from a two‐micrometer wide metallic top electrode. The resulting 0.002 μm2 area tunnel junction addresses a nanometer wide row of ≈2000 molecules. Active and remnant current–voltage measurements demonstrated that these devices can be reconfigurably switched and repeatedly cycled between high and low current states under ambient conditions. Control compounds, including a degenerate [2]catenane, were explored in support of the mechanical origin of the switching signature. These SWNT‐based MSTJs operate like previously reported silicon‐based MSTJs, but differently from similar devices incorporating bottom metal electrodes. The relevance of these results with respect to the choice of electrode materials for molecular electronics devices is discussed.
Co‐Conformational Distribution of Nanosized [2]Catenanes Determined by Pulse EPR Measurements
Authors: Jeschke Gunnar , Godt Adelheid
Published: December 2003

The co‐conformational ensembles of three differently sized [2]catenanes were studied by measuring pair correlation functions corresponding to the separation of nitroxide spin labels—one attached to each of the two macrocycles—with the double electron–electron resonance (DEER) experiment. A geometric model for the [2]catenanes was derived that approximates the macrocycles by circles and takes into account the topological constraint. Comparison of the experimental to the theoretically predicted pair correlation functions gives insight into the co‐conformational distribution and the size of the macrocycles. It was found that the macrocycles of the medium‐ and large‐sized catenanes in chloroform are close to fully expanded, while they are partially collapsed in glassyo‐terphenyl. For the small‐sized catenane, moderate interaction between the unsaturated sections of the macrocycles in chloroform is indicated by a slight overrepresentation of short label‐to‐label separations in the pair correlation function.
Cover Picture: Trends in Microfluidics with Complex Fluids (ChemPhysChem 12/2003)
Authors: Pfohl Thomas , Mugele Frieder , Seemann Ralf , Herminghaus Stephan
Published: December 2003

The cover picture shows…︁‥individual F‐actin filaments in lithographic microchannels (fluorescence microscopy image in the foreground, channel width 6 μm). Real‐time observation of the fluctuations of the fluorescently labeled molecules within the channels yields insight into the statistical mechanics of biopolymers in confined geometry. The impact of various geometrical parameters, such as channel curvature, may be studied by means of more intricate microfluidic setups (bright‐field microscopy image in the background). The goal is to understand the influence of geometric confinement, such as is present in microfluidic devices or in living cells, on the dynamics of complex matter. Find out more in the Concept Article by Herminghaus et al. on pp. 1291–1298.
Size of head phantoms for standard measurements of SAR due to wireless communication devices
Authors: Mochizuki Shoji , Watanabe Soichi , Taki Masao , Yamanaka Yukio , Shirai Hiroshi
Published: December 2003

In recent years, a project on the standardization of measurement methods for the head specific absorption rate (SAR) while using cellular phones has been in progress in Japan, Europe, and the United States. In order to achieve international coordination, it is desirable that head phantoms of the same shape be used in all countries; these are based on statistical data on European and American human sizes. However, the validity of application to the Japanese standard head phantoms which are generally of a larger size than the Japanese human size has not been established. Consequently, SAR measurements are made in this study with head phantoms based on the 90th‐percentile values of the head shape statistics of Europeans and Americans (E/A) and head phantoms based on the average Japanese adult male head shape (JP) in order to investigate the dependence of the head SAR on the phantom size. A numerical simulation is also performed, and the effect of the head phantom size on the current distribution on a cellular phone is also investigated. Based on these studies, it is found that the effect of the head phantom characteristics on the head SAR is small compared to the effect of the position of the cellular phone in the measurements, and that the effect on the current distribution on the cellular phone is also small. It is shown that for all three types of cellular phone models, that is, thick, thin, and folding types, that the E/A phantoms have roughly the same or larger maximum local SAR values than the JP phantoms. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(4): 82–91, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10083
Dynamic DR election for generating the multicast tree in PIM‐SM
Authors: Matsuzawa Tomofumi , Nakayama Masaya
Published: December 2003

In IP multicast streaming, PIM‐SM (protocol independent multicast sparse‐mode) is now becoming the mainstream. However, it may happen that the optimal tree cannot be generated, depending on the location of the DR (designated router, which is the router used to generate the tree and so on when there are multiple PIM‐SM routers in the segment) in some special topology. The means of handling such a situation is described only ambiguously in the PIM‐SM specification. Consequently, various problems now arise in implementation. This paper considers the dynamic determination of a DR that can generate the optimal tree even in such a special topology, and proposes a new additional protocol. Tree generation for various topologies is examined for the proposed method and the existing implementation, and it is shown that the proposed method is effective for any existing topology. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(4): 65–72, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10105
A QoS control method for MPEG video with an RTP monitoring agent for mobile streaming service
Authors: Yoshimura Takeshi , Ohya Tomoyuki , Kawahara Toshiro , Etoh Minoru
Published: December 2003

The authors propose a MPEG video quality control method for mobile streaming environment, in which the network agent called “RTP monitoring agent” is used. The RTP monitoring agent is placed at the border between the wired core network and the radio link. It feeds back QoS information, which contains the packet loss or delay fluctuation (jitter) observed by the agent itself, to the streaming server. Based on the feedback information sent from the monitoring agent and the feedback information sent from the streaming terminal, the streaming server decides whether the QoS degradation is due to network congestion or an error in the radio link. It then adjusts the transmission rate in the case of network congestion, and the packet loss immunity in the case of an error in the radio link. This paper also discusses a quality control method in MPEG video streaming that involves controlling file switching as well as the I‐picture insertion interval and the FEC packet transmission rate. A computer simulation shows that the MPEG video receiving quality is improved more in the quality control method using RTP monitoring agent than in the conventional rate control method. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(4): 54–64, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10106
Quasi‐optical antenna‐mixer array composed of a magnetic loop antenna operated at 10‐GHz band
Authors: Saito Hiroyuki , Nishimura Toshihiko , Yamamoto Manabu , Itoh Kiyohiko
Published: December 2003

The quasi‐optical antenna‐mixer is a receiving system that spatially receives RF signals and local oscillator (LO) signals and at the same time converts the RF signals to intermediate (IF) frequency signals. The line transmission loss, which causes a problem at millimeter wave frequencies, can be suppressed. In this paper, test fabrication and measurement of a quasi‐optical antenna‐mixer array receiving RF and LO signals with a magnetic loop antenna are carried out at 10 GHz and quasi‐optical mixing is shown to be possible. A two‐dimensional array antenna using this element is proposed. Its receiving characteristics are theoretically predicted. By changing the illumination angle or frequency of the LO, it is found that the receiving direction of the RF can be scanned. In addition, the suppression of RF and LO signals appearing at the output end is demonstrated. An experiment with a two‐dimensional array consisting of eight elements of quasi‐optical antenna‐mixers is carried out and the validity of the proposal is confirmed. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(4): 45–53, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10114
A scalable service control platform based on the locality of database access requests in the mobile communication network
Authors: Ogawa Takeshi , Masuda Etsuo
Published: December 2003

In regard to the scalable service control platform needed for realization of future mobile communication service, a new method of efficiently accessing distributed databases (DB) is proposed. Previously, as an access system plan to distributed DBs, a unicast‐type system in which the access request to a DB received from the network is transferred to the destination DB (System A) and a multicast system with multicast delivery (System B) have been proposed. In the former, the increased size of the destination decision table puts pressure on main memory. In the latter, multicast communication applies pressure every time on processor process capacity. Hence, sufficient scalability has not been obtained in either method. In the present paper, the existence of locality in the requirement for DB access among users is recognized. A hybrid system (System C) is proposed here in which unicast communication is applied for access by a few users with high access frequency, but multicast communication is used for access by the other, majority users. A system control parameter is introduced to select these communication methods. By choosing the value of this parameter optimally, the user accommodation limits in the conventional system are resolved. It is shown quantitatively that operation with a minimum amount of equipment is possible in a wide accommodation range. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(4): 1–15, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10164
Time‐domain analysis of arc voltage and electromagnetic noise caused by opening arc discharge between carbon and copper contacts
Authors: Koizumi Toshiaki , Takahashi Kumio , Ebara Yasuo , Sone Hideaki , Nemoto Yosiaki
Published: December 2003

In small commutation motors, arc discharges are generated between the brushes (carbon) and commutators (copper) in opposing positions, accompanied by electromagnetic noise. An arc discharge is produced both between the brush and commutator (Cu cathode) and between the commutator and brush (C cathode), and these two phenomena with different polarities cannot be separately observed from outside. In this investigation the arc discharges of different current polarities and their associated noise characteristics are analyzed. Experiments are performed with different opposing electrodes, consisting of C and Cu. The opening voltage is 40 V DC. The current in the closed state is 2 A. The load is an inductance of 0.85 mH. The arc voltage and noise when the electrical contacts are opened in both the Cu cathode and C cathode cases are analyzed as time series. It is found that the maximum noise level in each operation is about 20 dB higher for the Cu cathode case than for the C cathode case. The time of maximum noise generation in each operation is close to the time of arc extinction for the Cu cathode case but is in the middle of the arc discharge for the C cathode case. The time derivative of the voltage waveform near arc extinction and the amplitude of the noise waveform before detection are larger in the Cu cathode case than in the C cathode case. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(4): 92–99, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1188
Characterization of eutectic mixtures in different natural fat blends by thermal analysis
Authors: Solís‐Fuentes Julio A. , Durán‐de‐Bazúa Carmen
Published: December 2003

Samples of cacao butter (CB), mango seed almond fat (Mangifera indica var. Manila) (MAF), and zapote mamey seed almond fat (Pouteria sapota) (ZMAF), were analyzed for their fatty acid composition and were mixed according to a 3‐factor simplex‐lattice design. Mixtures were stabilized, their fusion and crystallization thermal behavior, and solid fat contents were evaluated using differential scanning calorimetry. Ternary phase behavior was analyzed with isosolid diagrams. Results showed that the main fatty acids in the fats were oleic, stearic, and palmitic acids: CB: 31.1, 35.5, and 27.8%; MAF: 37.5, 42.6 and 9.9%, and ZMAF: 50.0, 27.2 and 12.0%, respectively. Fusion behavior showed a single curve with only one maximum and one small shoulder for CB and MAF, and three maximum points for ZMAF. Crystallization was also a single curve with only one maximum for the three fats. Solid fat contents at 21.1 °C were: CB: 87.5; MAF: 68.5 and ZMAF: 6.6%. Ternary phase behavior showed that these fats can support preparation of mixtures with different compositions that could become equivalent to cocoa butter for use in alimentary, pharmaceutical, and cosmetic industries.
A gas chromatography‐mass spectrometry method for the detection of adipocere in grave soils
Authors: Forbes Shari L. , Keegan Jim , Stuart Barbara H. , Dent Boyd B.
Published: December 2003

Adipocere refers to a decomposition product, which forms due to the post‐mortem conversion of adipose tissue into a lipid mixture. During the conversion process, triglycerides present in the adipose tissue convert to free fatty acids via hydrolysis. Under the right conditions, hydrogenation of the free fatty acids will yield adipocere, which is chiefly comprised of saturated fatty acids. In a burial environment, adipocere may form macroscopically on the decomposing remains, but may also leach into the surrounding soil. This paper describes the development of a gas chromatography‐mass spectrometry method which allows for the quantitative analysis of trace levels of adipocere in grave soils.
Effect of the extraction and bleaching processes on jojoba (Simmondsia chinensis) wax quality
Authors: Tobares Lorena , Guzmán Carlos , Maestri Damián
Published: December 2003

The aim of the work was to evaluate the effect of extraction method and bleaching on the quality of jojoba waxes from Argentina. Jojoba waxes obtained by cold pressing, Golden wax (expeller‐pressed wax) and Lite wax (bleached wax) were analyzed using standard methods adopted as recommended practices by the American Oil Chemists Society. Physical parameters, fatty acid and alcohol compositions were unchanged among waxes. Cold‐pressed wax was noteworthy by its lower peroxide value, higher amounts of tocopherol and total phenol contents. Accordingly, it presented the best oxidative stability. Bleaching caused a strong decrease in both tocopherol and phenol contents; consequently the bleached wax showed poor oxidative stability.
Capillary GLC: a robust method to characterise the triglyceride profile of cocoa butter — results of an intercomparison study
Authors: Buchgraber Manuela , Ulberth Franz , Anklam Elke
Published: December 2003

The results of a method intercomparison study, in which 13 laboratories applied high‐temperature capillary GLC on fused‐silica columns coated with medium‐polarity stationary phases to determine the triglyceride profile of cocoa butter, are reported. The participants did not apply a uniform GLC procedure based on a standard method, but were requested to use their own methodology. However, certain requirements relating to the separation efficiency and the accuracy, had to be fulfilled. The relative standard deviation of the reproducibility was less than 5% for the major triglyceride components of cocoa butter. The results of the present study indicate that neither the type of capillary column employed nor sample injection techniques or other chromatographic conditions influenced to a measurable degree the agreement of results between the participating laboratories. Therefore, we conclude that high‐temperature capillary GLC is a robust and reliable technique for the characterisation of cocoa butter by determining its triglyceride pattern.