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41.
Meng-Yue Wu Ping Chen Ulrike Ziese Paul F.A. Alkemade Huub W.M. Salemink Henny W. Zandbergen 《Micron (Oxford, England : 1993)》2010,41(6):609-614
We studied the formation of locally coated sub-10-nm nanopores fabricated by ion-beam milling and ion-beam-induced deposition (IBID) in a thin silicon nitride membrane. Two typical precursor gases representing conductive ((CH3)3Pt(CpCH3), CPC for short) and insulating (tetra ethyl oxysilane, TEOS for short) material deposition are used. Three-dimensional electron tomography, EDX and EELS analysis are used to measure the changes in chemical composition and shape of the pores after their formation and at various stages of pore shrinkage. The formation and shrinkage are shown to be due to a shifting competition between IBID and material sputtering during ion-beam exposure. The chemical distribution at the rim of the nanopore is dependent on the precursor gases used: CPC forms a thin carbon layer with small embedded Pt particles at the top and inner surfaces of the nanopore, whereas TEOS forms SiOxCy with Ga particles dispersed at the rim of the nanopore. 相似文献
42.
van Merode AE Duval JF van der Mei HC Busscher HJ Krom BP 《Colloids and surfaces. B, Biointerfaces》2008,64(2):302-306
Initial adhesion is a determinant in the development of microbial biofilms. It is influenced, amongst others, by the surface hydrophobicity and the electrostatic characteristics of the substratum and adhering organisms. Enterococcus faecalis strains, grown in pure cultures, generally display subpopulations with different electrokinetic features, reflected in a bimodal electrophoretic mobility distribution. Here, the initial adhesion kinetics of five heterogeneous and five homogeneous E. faecalis strains were followed in a parallel-plate flow chamber. After 4h of flow, heterogeneous strains adhered in significantly higher numbers than homogeneous strains (7.3 x 10(6) and 1.9 x 10(6)cm(-2), respectively), but the initial deposition rates were not significantly influenced (740 and 600 cm(-2)s(-1), respectively). Apparently, initial deposition of bacteria is mainly governed by attractive Lifshitz-Van der Waals forces that overwhelm the electrostatic repulsion energy barrier, thus resulting in similar initial deposition rates for the various bacterial populations investigated. In contrast, during later stages of adhesion, bacteria in heterogeneous cultures likely experience a lower electrostatic repulsion from already adhering bacteria than bacteria in homogeneous cultures, thus allowing a closer proximity of the bacteria with respect to each other, which ultimately leads to increased adhesion after 4 h. 相似文献
43.
Boks NP Kaper HJ Norde W Busscher HJ van der Mei HC 《Colloids and surfaces. B, Biointerfaces》2008,67(2):276-278
Adhesion and desorption are simultaneous events during bacterial adhesion to surfaces, although desorption is far less studied than adhesion. Here, desorption of Staphylococcus epidermidis from substratum surfaces is demonstrated to be residence time dependent. Initial desorption rate coefficients were similar for hydrophilic and hydrophobic dimethyldichlorosilane (DDS)-coated glass, likely because initial desorption is controlled by attractive Lifshitz–Van der Waals interactions, which are comparable on both substratum surfaces. However, significantly slower decay times of the desorption rate coefficients are found for hydrophilic glass than for hydrophobic DDS-coated glass. This difference is suggested to be due to the acid–base interactions between staphylococci and these surfaces, which are repulsive on hydrophilic glass and attractive on hydrophobic DDS-coated glass. Final desorption rate coefficients are higher on hydrophilic glass than on hydrophobic DDS-coated glass, due to the so called hydrophobic effect, facilitating a closer contact on hydrophobic DDS-coated glass. 相似文献
44.
45.
Bernard A. Boukamp Mai T. N. Pham Dave H. A. Blank Henny J. M. Bouwmeester 《Solid State Ionics》2004,170(3-4):239-254
Accurate impedance measurements on differently sized samples of lead–zirconate–titanate (PbZr0.53Ti0.47O3, PZT) have been analyzed with a CNLS procedure, resulting in the separation of the ionic and electronic conductivities over a temperature range from 150 to 630 °C. At 603 °C the electronic conductivity shows approximately a (PO2)1/4 dependence, while the ionic conductivity remains constant. Below the Curie transition temperature the oxygen non-stoichiometry becomes frozen-in and the conductivities are strongly dependent on the sample history with respect to temperature sequence and ambient PO2. A tentative interpretation assumes defect association, i.e. formation of neutral [VPb–VO··]× complexes, and electron-hole transfer between lead sites and lead vacancies to control the oxygen ion conductivity in the tetragonal phase.
Annealing PZT-based devices at about 600 °C under low oxygen pressure (1 Pa oxygen) effectively decreases the low temperature electronic conductivity by a factor of 100 and the ionic conductivity by a factor of 10–15 with respect to normal air processing. 相似文献
46.
Sra AK Ewers TD Xu Q Zandbergen H Schaak RE 《Chemical communications (Cambridge, England)》2006,(7):750-752
By chemically modifying the nucleation burst that generates monodisperse FePt nanocrystals, a mixture of Pt and Fe(x)Pt(1-x) nanoparticles forms during a one-pot reaction that includes a small amount of Cu as a catalyst; size-selective precipitation yields a bi-disperse population of Fe(x)Pt(1-x) nanoparticles, which can assemble into high-quality AB2, AB5, and AB13 superlattice structures. 相似文献
47.
This paper introduces a general team balancing model. It first summarizes existing balancing methods. It is shown that for these methods it is difficult to meet all the conditions posed by Belbin on balanced teams. This mainly is caused by the complexity of the balancing problem. A mathematical model is then introduced that gives one the opportunity to take into account these conditions in mutual coherence and to generate a balanced team in terms of Belbin. A practical application is given. 相似文献
48.
Physicochemical and functional characterization of a biosurfactant produced by Lactococcus lactis 53
Rodrigues LR Teixeira JA van der Mei HC Oliveira R 《Colloids and surfaces. B, Biointerfaces》2006,49(1):79-86
Isolation and identification of key components of the crude biosurfactant produced by Lactococcus lactis 53 was studied. Fractionation was achieved by hydrophobic interaction chromatography which allowed the isolation of a fraction rich in glycoproteins. Molecular (by Fourier transform infrared spectroscopy) and elemental compositions (by X-ray photoelectron spectroscopy) were determined. Critical micelle concentration achieved for the isolated fraction was 14 g/l, allowing for a surface tension value of 36 mJ/m(2). Moreover, the isolated fraction, stable to pH changes between 5 and 9, was found to be an anti-adhesive and antimicrobial agent against several bacterial and yeast strains isolated from explanted voice prostheses, even at low concentrations. Further purification steps should be carefully analyzed as each purification step will increase the costs and decreases the amounts of biosurfactants recovered. 相似文献
49.
Bernard?A.?BoukampEmail author Matthijs?W.?den?Otter Henny?J.?M.?Bouwmeester 《Journal of Solid State Electrochemistry》2004,8(9):592-598
The conductivity relaxation (CR) method is often used for measuring the surface transfer rate,
Ktr, and the bulk diffusion coefficient,
for oxygen transport in mixed conducting oxides (MIECs). The time domain analysis of the obtained CR response is rather complex and is based on ideal behaviour for the diffusion process. It is quite favourable to perform the data analysis in the frequency domain, where non-ideal responses are easily recognised. Besides, frequency domain analysis (impedance spectroscopy) can yield reliable parameter estimates. Using a discrete Fourier-transform procedure, the time domain responses can be transformed to a frequency domain impedance-type expression. This approach can be applied to any system for which a driving force and a resulting flux can be defined.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003 相似文献
50.
Chen CS Feng SJ Ran S Zhu DC Liu W Bouwmeester HJ 《Angewandte Chemie (International ed. in English)》2003,42(42):5196-5198