Symbolic squares in regular local rings

In this paper we prove for several classes of ideals in regular local rings of equicharacteristic 0 that the symbolic square of the ideal contains no minimal generator of the ideal. Our techniques come from residual intersections, integral closures of ideals, and differentials. Received January 14, 1997; in final form March 20, 1997     

Simultaneous determination of alkylphenol ethoxylates and their biotransformation products by liquid chromatography/electrospray ionisation tandem mass spectrometry

Reversed-phase LC-MS/MS is used to determine major estrogenic alkylphenol ethoxylates (APEOs) and their biotransformation products. It allows the simultaneous analysis of eight APEOs, alkylphenoxy carboxylates (APECs) and alkylphenols (APs) in sewage treatment plant (STP) effluents in the same extract after solid-phase enrichment on polymeric Oasis HLB. As precursor ions, [APEO + NH4]+, [APEC - H]- and [AP - H]- were monitored. Instrumental limits of detection (LOD) were 2-600 pg, corresponding to sample concentrations of 0.04-12 ng l(-1), without correction for overall method recoveries. Matrix-induced signal suppression during electrospray ionisation (ESI) and extraction as well as overall method recoveries were assessed and the suitability of deuterated surrogates as internal standards was evaluated.     

Revisiting the S-Au(111) interaction: static or dynamic?

The Au-S interaction is probably the most intensively studied interaction of Au surfaces with nonmetals, as, for example, it plays an important role in Au ore formation(1) and controls the structure and dynamics of thiol-based self-assembled monolayers (SAMs). Various S-induced surface structures on Au(111) were recently reported for different conditions and predominantly interpreted in terms of a static Au surface. Here, we demonstrate that the Au(111) surface exhibits a very dynamic character upon interaction with adsorbed sulfur: large-scale surface restructuring and incorporation of Au atoms into a growing 2D AuS phase were observed in situ. These results provide new insight into the Au-S surface chemistry.     

Synthesis of TiO2 nanoparticles on the Au(111) surface

The growth of titanium oxide nanoparticles on reconstructed Au(111) was investigated by scanning tunneling microscopy and x-ray photoelectron spectroscopy. Ti was deposited by physical-vapor deposition at 300 K. Regular arrays of titanium nanoparticles form by preferential nucleation of Ti at the elbow sites of the herringbone reconstruction. The titanium oxide nanoclusters were synthesized by subsequent exposure to O(2) at 300 K. Two-and three-dimensional titanium oxide nanocrystallites form during annealing in the temperature range from 600 to 900 K. At the same time, the Au(111) surface assumes a serrated 110-oriented step-edge morphology suggesting step-edge pinning by titanium oxide nanoparticles. The oxidation state of the titanium oxide nanoparticles varies with annealing temperature. Specifically, annealing to 900 K results in the formation of stoichiometric TiO(2) nanocrystals as judged by the Ti(2p) binding energies measured in the x-ray photoelectron data. The nanodispersed TiO(2) on Au(111) is an ideal system to test the various models proposed for the enhanced catalytic reactivity of supported Au nanoparticles.     

Darstellung von polyfluororganotrichlorsilanen

The following substances could be prepared by Grignard reactions or by conversions with trichlorosilane: C₆F₅CH₂CHCH₂, C₆F₅(CH₂)₃SiCl₃, CF₃(CF₂)₉CH₂CHCH₂, CF₃(CF₂)₇(CH₂)₂SiCl₃, CF₃(CF₂)₁₁(CH₂)₃CHCH₂ und CF₃(CF₂)₁₁(CH₂)₅SiCl₃.They were characterized by spectroscopical and microanalytical methods.     

Characterization of H2 binding sites in prototypical metal-organic frameworks by inelastic neutron scattering

The hindered rotor transitions of H(2) adsorbed in the chemically related and prototypical porous metal-organic frameworks IRMOF-1, IRMOF-8, IRMOF-11, and MOF-177 were studied by inelastic neutron scattering to gain information on the specifics of H(2) binding in this class of adsorbents. Remarkably sharp and complex spectra of these materials signify a diversity of well-defined binding sites. Similarities in the spectral features as a function of H(2) loading and correlations with recent crystallographic studies were used to assign transitions ranging in rotational barrier from <0.04 to 0.6 kcal/mol as corresponding to localized adsorption sites on the organic and inorganic components of these frameworks. We find that binding of H(2) at the inorganic cluster sites is affected by the nature of the organic link and is strongest in IRMOF-11 in accord with our adsorption isotherm data. The sites on the organic link have lower binding energies, but a much greater capacity for increases in H(2) loading, which demonstrates their importance for hydrogen uptake by these materials.     

Structure of a surfactant-templated silicate framework in the absence of 3d crystallinity

The structure of a novel molecularly ordered two-dimensional (2D) silicate framework in a surfactant-templated mesophase has been established by using a combination of solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction, and quantum chemical and empirical force-field modeling. These materials are unusual in their combination of headgroup-directed 2D crystalline framework ordering, zeolite-like ring structures within the layers, and long-range mesoscopic organization without three-dimensional (3D) atomic periodicity. The absence of registry between the silicate sheets, resulting from the liquidlike disorder of the alkyl surfactant chains, has presented significant challenges to the determination of framework structures in these and similar materials lacking 3D crystalline order. Double-quantum (29)Si NMR correlation experiments establish the interactions and connectivities between distinct intra-sheet silicon sites from which the structure of the molecularly ordered inorganic framework is determined.     

Plasma Polymerization Inside Tubes in Hexamethyldisiloxanes and Ethyne Glow Discharges: Effects of Deposition Atmosphere on Wetting and Ageing in Solvents

The coating deposition inside tubes becomes increasingly important for fluidic applications, in which inner surfaces are chemically and mechanically strained by the flowing liquid and by scratching of particles. The developed process for tube coating, presented in this work, is based on the discharge in the precursor gas atmosphere between two mesh electrodes at the ends of the tube. The gas mixture is introduced on one end and pumped through the electrode on the other end. Igniting plasma inside the tube, the tube walls are the barrier to the atmosphere. Especially pulsed DC discharges for plasma polymerization in this alignment lead to good coating results, which is shown in this work focusing on deposition in pure and mixed hexamethyldisiloxane, ethyne, and oxygen atmospheres. Chemical binding, wetting, and ageing are strongly influenced by the choice of the gas mixtures. Sufficient oxygen partial pressure in the deposition atmosphere leads to hydrophilic behavior of the SiO₂-like polymer-like carbon coatings, all other applied atmospheres to generally hydrophobic behavior of pure and Si-doped plasma polymers, respectively.     

Inactivation of Vaccinia Virus by Natural Sunlight and by Artificial UVB Radiation

This study determined the sensitivity of vaccinia virus, an orthopox virus commonly used as a surrogate for variola virus (etiological agent of smallpox), exposed to UVB radiation emitted by a solar simulator, or to direct natural sunlight. The data obtained indicate that: (1) the virucidal effect of natural sunlight can be mimicked adequately by an artificial light source with similar spectral characteristics in the UVB, (2) viral sensitivity to UVB or to solar radiation can be correlated with experimental data previously obtained with UVC, (3) the correlation factor between virus inactivation by solar radiation (measured at 300 ± 5 nm) and by UVC (254 nm) is between 33 and 60, and (4) the sensitivity of viruses either dry on glass surfaces or in liquid suspension is similar when in the presence of similar amounts of cellular debris and growth media. The findings reported in this study should assist in estimating the threat posed by the persistence of virus during epidemics or after an accidental or intentional release.