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排序方式: 共有107条查询结果,搜索用时 15 毫秒
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Synthesis and XPS Analysis of nano-scaled Metal/Metaloxid Composites with Germanium, Tin, and Lead as Metallic Component tert-Butanolates of Germanium(II), tin(II), and lead(II) of the formula {M[O-C(CH3)3]2}n (M ? Ge, n = 2; M ? Sn, n = 2; M ? Pb, n = 3) as well as the corresponding heterometalalkoxides M′M2[O? C(CH3)3]6 (M ? Ge, M′ ? Sr, Ba; M ? Sn, M′ ? Ca, Sr, Ba; M ? Pb, M′ ? Ca, Ba) have been subject to a single precursor chemical vapour deposition (CVD) process. In this process the volatile precursor has been pyrolized under reduced pressure (0,1 Torr) on a graphit or metal substrate which has been heated by induction in a microwave field to about 300–500°C. The gases originating from this pyrolisis have been analyzed by means of a quadrupole mass spectrometer whereas the solid coating which contained the micro composite was characterized by X-ray diffraction, electron microscopy, EDX-analysis and XPS-spectra. In all cases the solid material contained two phases, in which the element M ((Ge), Sn, Pb) either had oxidation state 0 or +4 (in the surface of the solids made of germanium containing precursors only GeII along with Ge0 has been detected by XPS spectroscopy). The group 14-element in the starting material had thus undergone a disproportionation from the +2 oxidation state into a lower and a higher one by two units. The elemental phase and the phase containing the formal +4 cation which is amorphous in most cases and which approaches the formula MO2 or M′MO3 (M ? (Ge), Sn, Pb; M′ ? Ca, Sr, Ba) are uniformally distributed. The composites consist of ball shaped particles on which other smaller particles are placed in a fractal manner ressembling a black berry. In the case of the composite Sn · BaSnO3 the center of the ball shaped particles has been analyzed as pure elemental tin. The organic substituents of the precursors as well as the dynamic vacuum in the decomposition process seem to be responsible for the ball shaped nature of the solid material. In a test experiment gallium tri-tert-but-oxide has been used as precursor: again ball shaped particles are obtained which have the chemical composition Ga2O3 but which contain no elemental gallium. 相似文献
45.
Schoonbeek FS van Esch JH Hulst R Kellogg RM Feringa BL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(14):2633-2643
Several geminal bis-urea compounds were synthesised by means of an acid-catalysed condensation of various benzaldehydes with different monoalkylureas. Many of these compounds form thermoreversible gels with a number of organic solvents at very low concentrations (<3mM) and which are stable to temperatures higher than 100 degrees C. Electron microscopy revealed a three-dimensional (3D) network of intertwined fibres, which are several tens of micrometers long and have a width ranging from approximately 30 to 300 nm. The possible aggregate forms and aggregate symmetries were evaluated by means of molecular mechanics calculations. 1H NMR, 2D NMR, 13C NMR and 13C-CP/MAS NMR techniques were used to obtain information about the aggregation and possible aggregate symmetry of geminal bis-ureas in solution, in the gel state, and in the solid state. 相似文献
46.
Marsman AW Havenith RW Bethke S Jenneskens LW Gleiter R van Lenthe JH Lutz M Spek AL 《The Journal of organic chemistry》2000,65(15):4584-4592
Long-range sigma-pi interactions in tetrahydro4H-thiopyran end-capped oligo(cyclohexylidenes) were identified by He(I) photoelectron spectroscopy (PES) and ab initio RHF/6-31G* calculations. The vertical ionization energies Ivj of the highest occupied molecular orbitals (MO's) were assigned using Koopmans' theorem (Iv,j = -epsilonj) and by correlation with the ionizations of related reference compounds. The experimental (PES) and theoretical (RHF/6-31G*) results are in good agreement. For tercyclohexylidene derivatives which contain two nonconjugated pi-bonds splittings deltaIv,j of the pi-bands in the range from approximately 0.5 to 0.7 eV (delta-epsilonj approximately 0.6 to 0.9 eV). For the bi- and tercyclohexylidene compounds containing two sulfur atoms at their alpha- and omega-end positions the pi-type sulfur lone pair bands [Lppi(S)] split significantly by deltaIvj approximately 0.3 to 0.4 eV (delta-epsilonj approximately 0.3 to 0.4 eV), i.e. sigma-pi interactions over distances of ca. 8 and 12 A, respectively, occur. The magnitude of the interactions and the observed splittings are independent of the anti and syn conformations of the oligo(cyclohexylidene) hydrocarbon skeletons. RHF/6-31G* Natural Bond Orbital analyses reveal that the Hax-C-C-Hax precanonical MO's (PCMO's) centered on the cyclohexyl-type rings are paramount for the relay of the through-bond sigma-pi interactions; no through-space sigma-pi interactions were identified. 相似文献
47.
H.-G. Clerc K.-H. Schmidt H. Wohlfarth W. Lang H. Schrader K.E. Pferdekämper R. Jungmann M. Asghar J.P. Bocquet G. Siegert 《Nuclear Physics A》1975,247(1):74-90
The nuclear charge distribution of fission products with mass numbers A = 90, 91, 94, 99, 100, 101 and 104 provided by the mass separator “Lohengrin” was measured. Adjacent elements in the group of the light fission products could be separated by their different energy loss in a carbon absorber. The Z-yields were found to be strongly dependent on the kinetic energy of the fission products. The widths of the nuclear charge distributions are very small, in general, and strongly dependent on A as well as on the kinetic energy. The influence of the neutron evaporation and odd-even effects are clearly detected. An asymmetric nuclear charge distribution was found for A = 104 indicating the suppression of fission fragments with Z = 43. The average nuclear charges of the fission products at their average kinetic energy are in good agreement with the results from measurements of the number of β-decays and K X-ray measurements. The average nuclear charge of the isobar A = 132 was measured at its average kinetic energy with a calibrated secondary electron detector to be Z = 51.14 ± 0.15 which is in very good agreement with the radiochemical results. Thus previous physical measurements indicating a large independent yield for the doubly magic nucleus 132Sn could not be confirmed. 相似文献
48.
Thomas Schlichthaerle Alexandra S. Eklund Florian Schueder Maximilian T. Strauss Christian Tiede Alistair Curd Jonas Ries Michelle Peckham Darren C. Tomlinson Ralf Jungmann 《Angewandte Chemie (International ed. in English)》2018,57(34):11060-11063
Optical super‐resolution techniques allow fluorescence imaging below the classical diffraction limit of light. From a technology standpoint, recent methods are approaching molecular‐scale spatial resolution. However, this remarkable achievement is not easily translated to imaging of cellular components, since current labeling approaches are limited by either large label sizes (antibodies) or the sparse availability of small and efficient binders (nanobodies, aptamers, genetically‐encoded tags). In this work, we combined recently developed Affimer reagents with site‐specific DNA modification for high‐efficiency labeling and imaging using DNA‐PAINT. We assayed our approach using an actin Affimer. The small DNA‐conjugated affinity binders could provide a solution for efficient multitarget super‐resolution imaging in the future. 相似文献
49.
Hans-Kristian Walter Klaus Jungmann 《Zeitschrift fur Physik C Particles and Fields》1992,56(Z1):S135-S142
The experimental status of generation number violating muon and kaon decays is reviewed. We concentrate on three experiments
with a large PSI contribution, neutrinoless muon-electron conversion, muonium-antimuonium conversion and the decayK
+→π
+. The SINDRUM II experiment at PSI searches for the coherent conversion of a muon into an electron in titanium. The design
and construction of the SINDRUM II detector and the results of the first data-taking period in 89 are presented. In total
3.2 million events have been analyzed and no candidate for the processμ
−
Ti→e
+
Ti has been found. Using two independent determinations of the total number of muon stops an upper limit ofB
μe
<4.4×10−12 (90% C.L.) is obtained. The plans to lower the sensitivity by two orders of magnitude are discussed. A muonium-antimuonium
conversion experiment is being set up at PSI using the refurbished SINDRUM I detector. The goal of the experiment is to improve
the sensitivity for the effective coupling constant
by a factor of ∼100. Finally a new proposal E865 has been accepted at BNL to improve the sensitivity for the branching ratio
of the decayK
+→π
+ by a factor 70 to 3×10−12.
Representing the SINDRUM II Collaboration: (ETH Zürich, Univ. Zürich, Paul Scherrer Institute Villigen, RWTH Aachen, Univ.
Tbilisi) 相似文献
50.
Abbott T Akiba Y Beavis D Bloomer MA Bond PD Chasman C Chen Z Chu YY Cole BA Costales JB Crawford HJ Cumming JB Debbe R Engelage J Fung SY Gushue S Hamagaki H Hansen O Hayano RS Hayashi S Homma S Huang HZ Ikeda Y Juricic I Kang J Katcoff S Kaufman S Kimura K Kitamura K Kurita K Ledoux RJ Levine MJ Miake Y Morse RJ Moskowitz B Nagamiya S Olness J Parsons CG Remsberg LP Sakurai H Sarabura M Stankus P Steadman SG Stephans GS Sugitate T Tannenbaum MJ van Dijk JH Videbaek F Vient M Vincent P 《Physical review D: Particles and fields》1992,45(11):3906-3920