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K. Tonisch F. Weise M. Stubenrauch V. Cimalla G. Ecke F. Will H. Romanus S. Mrotzek H. Hofmeister M. Hoffmann D. Hülsenberg O. Ambacher 《Physica E: Low-dimensional Systems and Nanostructures》2007,38(1-2):40
We report on the growth of silicon nanowires on photostructurable glass by low-pressure chemical vapour deposition. Thereby, no additional catalyst was needed to stimulate the growth process. Instead, a self-organized crystallization process leads to the formation of metallic clusters and seed crystals within the glass, which are supposed to initialize the nanowire growth. The nanowires were contacted by direct deposition of Pt using a focussed ion beam system and characterized electrically. 相似文献
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Büscher K Helm CA Gross C Glöckl G Romanus E Weitschies W 《Langmuir : the ACS journal of surfaces and colloids》2004,20(6):2435-2444
Experiments were carried out on a water-based ferrofluid (gamma-Fe2O3 with carboxydextran shell) using photon correlation spectroscopy (PCS), atomic force microscopy, and magnetic nanoparticle relaxation measurements. The experiments were designed with the aim to relate the Néel signals that are in theory generated by large single core particles with nanoscopic properties, that is, particle size, particle size distribution, shell properties, and aggregation. For this purpose, the ferrofluid was fractionated by magnetic fractionation and size exclusion chromatography. Nanoparticles adsorbed onto positively charged substrates form a two-dimensional monolayer. Their mean core diameters are in the range of 6 to about 20 nm, and particles above 10 nm are mostly aggregates. The hydrodynamic particle diameters are between 13 and 80 nm. The core diameter of the smallest fraction is confirmed by X-ray reflectometry; the surface coverage is controlled by bulk diffusion. Comparison with the hydrodynamic radius yields a shell thickness of 3.8 nm. Considering the shell thickness to be constant for all particles, it was possible to calculate the apparent particle diameter in the original ferrofluid from the PCS signals of all fractions. As expected, the small cores yielded no Néel relaxation signals in freeze-dried samples; however, the fractions containing mostly aggregates yielded Néel relaxation signals. 相似文献
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Romanus K Van Neer W Marinova E Verbeke K Luypaerts A Accardo S Hermans I Jacobs P De Vos D Waelkens M 《Analytical and bioanalytical chemistry》2008,390(2):783-793
Burned greasy deposits were found inside shells of the large Nile bivalve Chambardia rubens, excavated in an eight- to tenth- century AD church of the Coptic monastery of Bawit, Egypt, and supposedly used as oil lamps.
The residues were subjected to a combination of chromatographic residue analysis techniques. The rather high concentrations
of unsaturated fatty acids, as analysed by gas chromatography (GC) in the methylated extract, suggest the presence of a vegetal
oil. Analysis of the stable carbon isotopes (δ
13C values) of the methyl esters also favoured plants over animals as the lipid source. In the search for biomarkers by GC coupled
to mass spectrometry on a silylated extract, a range of diacids together with high concentrations of 13,14-dihydroxydocosanoate
and 11,12-dihydroxyeicosanoate were found. These compounds are oxidation products of erucic acid and gondoic acid, which are
abundantly present in seeds of Brassicaceae plants. Liquid chromatography coupled to mass spectrometry analysis showed low
concentrations of unaltered triglycerides, but revealed sizeable amounts of triglycerides with at least one dihydroxylated
acyl chain. The unusual preservation of dihydroxylated triglycerides and α,ω-dicarboxylic acids can be related to the dry preservation conditions. Analysis of the stereoisomers of the dihydroxylated
fatty acids allows one to determine whether oxidation took place during burning of the fuel or afterwards. The results prove
that the oil of rapeseed (Brassica napus L.) or radish (Raphanus sativus L.) was used as illuminant in early Islamic Egypt, and that not only ceramic lamps but also mollusk shells were used as fuel
containers. 相似文献
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Axel Romanus Helmut Müller Dietmar Kirsch 《Fresenius' Journal of Analytical Chemistry》1991,340(6):363-370
Summary Routine analysis of brine for trace metals is important for safe and economical production in the alkali chloride electrolysis. As opposed to many spectroscopic techniques, trace metal determination by adsorptive stripping voltammetry (AdSV) is shown to be performed directly in brine. With minimal sample preparation chromium(VI), iron(III), nickel(II), cobalt(II), titanum(IV), manganese(II), molybdenum(VI) and vanadium(V) can be determined within minutes. The influence of parameters such as pH-value, supporting electrolyte solution, concentration of complexing reagents and possible interferents are investigated for optimal experimental conditions. Minimum detection limits are less than 5 ng/g for all trace metals except 1 ng/g for chromium(VI), cobalt(II) and molybdenium(VI) for 40 s adsorption periods with precisions of better than 7%. AdSV with linear or differential pulse scan is discussed. 相似文献
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Ortwin Farle Stefan Burgard Romanus Dyczij-Edlinger 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(3):279-294
Parametric model-order reduction (pMOR) has become a well-established technology for analysing large-scale systems with multiple parameters. However, the treatment of non-affine parameters is still posing significant challenges, because projection-based order-reduction methods cannot be applied directly. A common remedy is to establish affine parameter-dependencies approximately, but present extraction methods do not take important system properties, such as passivity, into account. This article proposes a new order-reduction approach that preserves passivity, reciprocity and causality and applies to a wide class of linear time-invariant (LTI) systems. We present the theory of the suggested method and demonstrate its practical usefulness by numerical examples taken from computational electromagnetics. 相似文献
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Jan Baeten Kerlijne Romanus Patrick Degryse Wim De Clercq Hilde Poelman Kristin Verbeke Anja Luypaerts Marc Walton Pierre Jacobs Dirk De Vos Marc Waelkens 《Microchemical Journal》2010,95(2):227-234
During archaeological excavations of the Castle of Middelburg (Belgium), a 16th century ceramic vessel containing a greasy substance was found. A wide range of chemical techniques was applied on what was presumed to be an ointment to reveal its nature and function. The organic fraction, constituting about 24 wt.%, was analyzed by chromatography and mass spectrometry and consists of beeswax next to smaller amounts of a triglyceride lipid source. Infrared analyses indicated the presence of calcium carboxylate soaps. The inorganic ingredients represent about 30% of the total mass. While calcium, lead and iron were detected by elemental analysis, X-ray diffraction revealed calcium sulfate (gypsum) and lead sulfate as major minerals. Detailed study by X-ray photoelectron spectroscopy confirmed the presence of lead as a divalent species. Altogether, these results point to a medicinal formulation of a lead plaster, used for treating bruises, mixed with beeswax, which was added for easy application on the skin. It is further assumed that lead carboxylates, originally present in the sample, reacted with gypsum, resulting in the formation of calcium carboxylates and lead sulfate. Gypsum could have been added to whiten or to strengthen the plaster. Hence, the analyses confirm the presumed medicinal nature of the find and add it to the list of very rare finds of preserved historical ointments. 相似文献
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Graham?J?TizzardEmail author Simon?J?Coles Mark?Edwards Romanus?Oforbike?Onyeabo Mark?Allen John?Spencer 《Chemistry Central journal》2013,7(1):182
Background
4-substituted methylidene oxindoles are pharmacologically important. Detailed analysis and comparison of all the interactions present in crystal structures is necessary to understand how these structures arise. The XPac procedure allows comparison of complete crystal structures of related families of compounds to identify assemblies that are mainly the result of close-packing as well as networks of directed interactions.Results
Five 4-substituted methylidene oxindoles have been synthesized by the Knoevenagel condensation of oxindole with para-substituted aromatic aldehydes and were characterized in the solid state by x-ray crystallography. Hence, the structures of (3E)-3-(4-Bromobenzylidene)-1,3-dihydro-2H-indol-2-one, 3a, (3E)-3-(4-Chlorobenzylidene)-1,3-dihydro-2H-indol-2-one, 3b, (3E)-3-(4-Methoxybenzylidene)-1,3-dihydro-2H-indol-2-one, 3c, (3E)-3-(4-Methylbenzylidene)-1,3-dihydro-2H-indol-2-one, 3d and (3E)-3-(4-Nitrobenzylidene)-1,3-dihydro-2H-indol-2-one, 3e, were elucidated using single crystal X-ray crystallography.Conclusions
A hydrogen bonded dimer molecular assembly or supramolecular construct was identified in all the crystal structures examined along with a further four 1D supramolecular constructs which were common to at least two of the family of structures studied. The 1D supramolecular constructs indicate that once the obvious strong interaction is satisfied to form hydrogen bonded dimer it is the conventionally weaker interactions, such as steric bulk and edge-to-face interactions which compete to influence the final structure formation.8.
In this paper, an iterative algorithm that approximates solutions of split equality fixed point problems (SEFPP) for quasi-?-nonexpansive mappings is constructed. Weak convergence of the sequence generated by this algorithm is established in certain real Banach spaces. The theorem proved is applied to solve split equality problem, split equality variational inclusion problem, and split equality equilibrium problem. Finally, some numerical examples are given to demonstrate the convergence of the algorithm. The theorems proved improve and complement a host of important recent results.
相似文献9.
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