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41.
T. Brousse G. Poullain J.F. Hamet H. Murray B. Raveau 《Physica C: Superconductivity and its Applications》1990,170(5-6):545-551
Thin films of Bi2Sr2CaCu2O8 and (Bi, Pb)2Sr2Ca2Cu3O10 have been prepared on monocrystalline (100) MgO substrates, using a laser ablation method with post annealing treatment. The influence of substrate temperature and oxygen pressure during deposition were investigated. SEM observations, EDS analysis, electric and magnetic measurements have been used to characterize the films. Superconducting “2212” films, with Tc(R = 0) at 80–83 K and Jc (50 K) up to 5 × 105 A/cm2, have been currently achieved, while Pb-doped “2223” films exhibit Tc as high as 110 K with Jc = 5 × 104 A/cm2 at 77 K. The effect of annealing at low temperature (350°C) in an argon flow has been studied for the 2212 phase, it shows the influence of the oxygen non-stoichiometry, i.e. of the hole carrier density upon Tc's which can be measured up to 89 K (zero resistance). 相似文献
42.
Bearden IG Beavis D Besliu C Blyakhman Y Budick B Bøggild H Chasman C Christensen CH Christiansen P Cibor J Debbe R Enger E Gaardhøje JJ Germinario M Hagel K Hansen O Holm A Holme AK Ito H Jakobsen E Jipa A Jundt F Jørdre JI Jørgensen CE Karabowicz R Keutgen T Kim EJ Kozik T Larsen TM Lee JH Lee YK Løvhøiden G Majka Z Makeev A McBreen B Mikelsen M Murray M Natowitz J Nielsen BS Norris J Olchanski K Olness J Ouerdane D Płaneta R Rami F Ristea C Röhrich D Samset BH Sandberg D Sanders SJ 《Physical review letters》2003,90(10):102301
We present ratios of the numbers of charged antihadrons to hadrons (pions, kaons, and protons) in Au+Au collisions at sqrt[s(NN)]=200 GeV as a function of rapidity in the range y=0-3. While the ratios at midrapidity are approaching unity, the K(-)/K(+) and p;/p ratios decrease significantly at forward rapidities. An interpretation of the results within the statistical model indicates a reduction of the baryon chemical potential from mu(B) approximately 130 MeV at y=3 to mu(B) approximately 25 MeV at y=0. 相似文献
43.
We consider two analogues of associativity for ternary algebras: total and partial associativity. Using the corresponding ternary associators, we define ternary analogues of alternative and assosymmetric algebras. On any ternary algebra the alternating sum [a, b, c] = abc − acb − bac + bca + cab − cba (the ternary analogue of the Lie bracket) defines a structure of an anticommutative ternary algebra. We determine the polynomial identities of degree ?7 satisfied by this operation in totally and partially associative, alternative, and assosymmetric ternary algebras. These identities define varieties of ternary algebras which can be regarded as ternary analogues of Lie and Malcev algebras. Our methods involve computational linear algebra based on the representation theory of the symmetric group. 相似文献
44.
Hydrophobic bacteria, like colloidal solids, can spontaneously adsorb onto fluid-fluid interfaces and modify their mechanical properties. In this study, two strains of bacteria--Acinetobacter venetianus RAG-1 and Rhodococcus erythropolis 20S-E1-c--were prepared in their stationary (i.e. non-dividing) phase in the absence of biosurfactants; the cells were then used as emulsifiers to stabilize n-hexadecane droplets in aqueous environments. Using the micropipette technique, colloidal stability of the bacteria-coated droplets was examined through direct-contact experiments. Both types of bacteria were seen to function as effective stabilizers, although the Acinetobacter venetianus RAG-1 film provided stronger resistance to droplet-droplet coalescence. In addition to creating steric barriers, the adsorbed bacteria also interacted with one another at the interface, giving rise to higher order rheological properties. A technique of directly probing the mechanical properties of the emulsion drop surfaces (i.e. the adsorbed films) on the micrometre-scale revealed that (a) the films behaved as purely elastic sheets, and (b) with a reduction in cell concentration in the aqueous phase, less oil was emulsified, but the elastic moduli of the adsorbed films remained unchanged (suggesting an "all or none" adsorption process). These results are in contrast to a previous macroscopic (i.e. millimetre-scale) study, which showed that the absorbed films were viscoelastic, with the apparent elastic moduli depending strongly on cell concentration. The rheological properties of these bacteria-adsorbed interfaces appeared therefore to be length scale-dependent. 相似文献
45.
Ranganathan S Guo R Murray RW 《Langmuir : the ACS journal of surfaces and colloids》2007,23(13):7372-7377
Electron-transfer reactions of redox solutes at electrode/solution interfaces are facilitated when their formal potentials match, or are close to, the energy of an electronic state of the electrode. Metal electrodes have a continuum of electronic levels, and redox reactions occur without restraint over a wide span of electrode potentials. This paper shows that reactions on electrodes composed of films of metal nanoparticles do have constraints when the nanoparticles are sufficiently small and molecule-like so as to exhibit energy gaps, and resist electron transfers with redox solutes at potentials within the energy gap. When solute formal potentials are near the electronic states of the nanoparticles in the film, electron-transfer reactions can occur. The electronic states of the nanoparticle film electrodes are reflected in the formal potentials of the electrochemical reactions of the dissolved nanoparticles at naked metal electrodes. These ideas are demonstrated by voltammetry of aqueous solutions of the redox solutes methyl viologen, ruthenium hexammine, and two ferrocene derivatives at films on electrodes of 1.1 nm core diameter Au nanoparticles coated with protecting monolayers of phenylethanethiolate ligands. The methyl viologen solute is unreactive at the nanoparticle film electrode, having a formal potential lying in the nanoparticle's energy gap. The other solutes exhibit electron transfers, albeit slowed by the electron hopping resistance of the nanoparticle film. The nanoparticles are not linked together, being insoluble in the aqueous medium; a small amount of an organic additive (acetonitrile) facilitates observing the redox solute voltammetry. 相似文献
46.
Triangles and tetrahedra: metal directed self-assembly of metallo-supramolecular structures incorporating bis-beta-diketonato ligands 总被引:1,自引:0,他引:1
Clegg JK Lindoy LF Moubaraki B Murray KS McMurtrie JC 《Dalton transactions (Cambridge, England : 2003)》2004,(16):2417-2423
The interaction of six aryl-linked bis-beta-diketones, including a new naphthylene linked species, with copper(II), iron(III) and, in one instance gallium(III), has been investigated with the aim of obtaining metallo-supramolecular assemblies exhibiting different geometries. New examples of two assembly types incorporating the above bis-beta-diketones (L) were generated. The first type is represented by a range of molecular triangles of formula [Cu(3)(L-H(2))(3)](solvent)(n) while the second is given by a corresponding selection of less-common neutral molecular tetrahedra of formula [Fe(4)(L-H(2))(6)](solvent)(n) as well as [Ga(4)(L-H(2))(6)].8.5THF.0.5H(2)O; an example of each type has been characterised by X-ray crystallography. A magnetochemical investigation of [Fe(4)(-H(2))(6)].6THF is reported. The susceptibility is Curie like and consistent with very weak coupling occurring between the iron(III) d(5)(high spin) centres. The X-ray structures of two trinuclear copper(II) as well as a tetranuclear iron(III) and a tetranuclear gallium(III) assembly confirm their discrete triangular and tetrahedral geometries, respectively. The structure of the gallium(III) species is closely related to that of the corresponding iron(III) species. The tetrahedral structures provide rare examples of such assemblies encapsulating guest solvent molecules--in each case tetrahydrofuran is incorporated in the central cavity. 相似文献
47.
Turner DR Chesman AS Murray KS Deacon GB Batten SR 《Chemical communications (Cambridge, England)》2011,47(37):10189-10210
The chemistry of the anions dicyanamide and tricyanomethanide (dca and tcm, respectively) has produced a plethora of discoveries over the past few decades, particularly in relation to transition-metal coordination polymers with magnetic coupling. Over recent years there have been an increasing number of reports of heterofunctionalised cyano-containing anions, typically derivatives of dicyanomethanide. Our own group has been particularly concerned with the amide- and nitroso-functionalised anions carbamoyldicyanomethanide (cdm) and dicyanonitrosomethanide (dcnm), respectively. This feature article examines the fascinating diversity of materials and complexes that can be obtained using small cyano anions, ranging from coordination polymers to heterometallic clusters and hydrogen bonding networks. In particular, we focus on results from our own laboratories in the past few years. The magnetic properties of these materials are briefly discussed. 相似文献
48.
Clarke DJ Murray E Hupp T Mackay CL Langridge-Smith PR 《Journal of the American Society for Mass Spectrometry》2011,22(8):1432-1440
Noncovalent protein–ligand and protein–protein complexes are readily detected using electrospray ionization mass spectrometry
(ESI MS). Furthermore, recent reports have demonstrated that careful use of electron capture dissociation (ECD) fragmentation
allows covalent backbone bonds of protein complexes to be dissociated without disruption of noncovalent protein–ligand interactions.
In this way the site of protein–ligand interfaces can be identified. To date, protein–ligand complexes, which have proven
tractable to this technique, have been mediated by ionic electrostatic interactions, i.e., ion pair interactions or salt bridging.
Here we extend this methodology by applying ECD to study a protein–peptide complex that contains no electrostatics interactions.
We analyzed the complex between the 21 kDa p53-inhibitor protein anterior gradient-2 and its hexapeptide binding ligand (PTTIYY).
ECD fragmentation of the 1:1 complex occurs with retention of protein–peptide binding and analysis of the resulting fragments
allows the binding interface to be localized to a C-terminal region between residues 109 and 175. These finding are supported
by a solution-phase competition assay, which implicates the region between residues 108 and 122 within AGR2 as the PTTIYY
binding interface. Our study expands previous findings by demonstrating that top-down ECD mass spectrometry can be used to
determine directly the sites of peptide–protein interfaces. This highlights the growing potential of using ECD and related
top-down fragmentation techniques for interrogation of protein–protein interfaces. 相似文献
49.
John J. Porter Joel Luke Murray Kenneth B. Takvorian 《Journal of heterocyclic chemistry》1973,10(1):43-46
The complexing ability of derivatives of azobenzene (I) is well known (I) and responsible for the production of a wide variety of dyestuffs and analytical chemicals. While the azo group generally participates in the coordination, the determination of the degree of its interaction is complicated by other functional groups which are also coordinated with the transition metal. In a previous publication (2), we reported the preparation of the silver and palladium complexes of benzo[c]cinnoline (II) and proposed that these results might be used to explain the electron donor properties of azobenzene. We are now reporting the preparation of some additional complexes with ligands containing the azo group. 相似文献
50.
Andreas Markwitz Geoffrey Vaughan White William Joseph Trompetter Ian William Murray Brown 《Mikrochimica acta》2001,137(1-2):49-56
Thin SiO2 layers were produced by thermal oxidation of Si wafer material. To study the effect of nitridation on the oxide layers, the
specimens were nitrided in a furnace at high temperature. Non-destructive ion beam analysis was performed to determine changes
in the elemental concentrations and depth profiles of the major components. In particular, N and O concentrations were measured
using the non-resonant nuclear reactions 14N(d, α)12C and 16O(d, p)17O, respectively. To obtain depth profiles of the as-prepared and nitrided specimens, the samples were measured with RBS and
heavy ion elastic recoil detection analysis. The ion beam analyses revealed an increase in thickness of the SiO2 layers with temperature. The specimens nitrided at 1200 °C were almost free of N. Surface topology investigations with scanning
electron microscopy revealed concentric annular artificial patterns at the surfaces. In the centre of the pattern, only silicon
was measured. Additionally, a band consisting of Si, O, and N surrounding the pattern was discovered. The findings are in
agreement with specimens prepared at higher temperatures.
Received June 19, 2000. Revision December 9, 2000. 相似文献