Biomedical subjects

L Schlapbach

Publications and source records attributed to L Schlapbach.

At least 19 recordsLinked to original sources

PubMed2001

Hydrogen-storage materials for mobile applications.

Mobility--the transport of people and goods - is a socioeconomic reality that will surely increase in the coming years. It should be safe, economic and reasonably clean. Little energy needs to be expended to overcome potential energy changes, but a great deal is lost through friction (for cars about 10 kWh per 100 km) and low-efficiency energy conversion. Vehicles can be run either by connecting them to a continuous supply of energy or by storing energy on board. Hydrogen would be ideal as a synthetic fuel because it is lightweight, highly abundant and its oxidation product (water) is environmentally benign, but storage remains a problem. Here we present recent developments in the search for innovative materials with high hydrogen-storage capacity.

Journal Article↗

PubMed2001

Formation of a stable decagonal quasicrystalline Al-Pd-Mn surface layer.

We report the in situ formation of an ordered equilibrium decagonal Al-Pd-Mn quasicrystal overlayer on the fivefold symmetric surface of an icosahedral Al-Pd-Mn monograin. The decagonal structure of the epilayer is evidenced by x-ray photoelectron diffraction, low-energy electron diffraction, and electron backscatter diffraction. This overlayer is also characterized by a reduced density of states near the Fermi edge as expected for quasicrystals. This is the first time that a millimeter-size surface of the stable decagonal Al-Pd-Mn is obtained, studied, and compared to its icosahedral counterpart.

Journal Article↗

PubMed2001

Chemical nucleation for CVD diamond growth.

A new nucleation method to form diamond by chemically pretreating silicon (111) surfaces is reported. The nucleation consists of binding covalently 2,2-divinyladamantane molecules on the silicon substrate. Then low-pressure diamond growth was performed for 2 h via microwave plasma CVD in a tubular deposition system. The resulting diamond layers presented a good cristallinity and the Raman spectra showed a single very sharp peak at 1331 cm(-1), indicating high-quality diamonds.

Journal Article↗

PubMed2001

Adsorption and Bioactivity of Protein A on Silicon Surfaces Studied by AFM and XPS.

The adsorption of protein A on silicon surfaces was studied by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy. The deposition was made statically from various concentrations of protein A in water solution. The biological activity was checked by the immobilization of rabbit immunoglobulin G. The protein adsorption occurs in least two different phases and leads to a multilayer film. The first monolayer of proteins is rapidly adsorbed on the surface. The adsorption of the second layer of proteins occurs much more slowly (a thousand times slower) and also involves the third monolayer. The protein A of the first monolayer is denaturated and biologically inactive. On the contrary, the proteins of the second monolayer keep their natural diameter and remain biologically active. AFM artifacts such as the convolution with small objects and the resulting estimation of the coverage ratio are discussed. Copyright 2001 Academic Press.

Journal Article↗

PubMed2000

Hydrogen atoms cause long-range electronic effects on graphite

We report on long-range electronic effects caused by hydrogen-carbon interaction at the graphite surface. Two types of defects could be distinguished with a combined mode of scanning tunneling microscopy and atomic force microscopy: chemisorption of hydrogen on the basal plane of graphite and atomic vacancy formation. Both types show a (sqrt[3]xsqrt[3])R30 degrees superlattice in the local density of states but have a different topographic structure. The range of modifications in the electronic structure, of fundamental importance for electronic devices based on carbon nanostructures, has been found to be of the order of 20-25 lattice constants.

Journal Article↗

PubMed2000

Surface and friction characterization by thermoelectric measurements during ultrasonic friction processes

Even though friction is one of the oldest problems in physics many aspects of friction processes are not clear today. We present an experimental setup, which permits the study of tribological systems by measuring the dissipated heat at the interface of two surfaces during a friction process with a time resolution of 1 ms. The apparatus is based on a standard ultrasonic wire-bond machine used in semiconductor industries to connect the internal semiconductor die to the external leads, but the standard bond wire is replaced by a thermocouple. To demonstrate the ability of the apparatus it will be shown that bond substrates used in semiconductor industries can be unequivocally characterized.

Journal Article↗

PubMed2000

Evaluating mechanical adhesion of sol-gel titanium dioxide coatings containing calcium phosphate for metal implant application.

The adhesion of thin (< 10 microm) sol-gel calcium phosphate-titanium dioxide films bonded to a titanium substrate was studied using two different tests: a rotating-bending test and a tensile bond test. The former evaluates the impact of both the coating procedure and the surface pre-treatment on the resistance to fatigue of the substrate as well as the adhesion of the coating; the latter measures the tensile adhesion strength of the coating. Both tests gave similar results. A reduction of the thickness of the coating or an increase of the roughness of the substrate improves the quality of the interface. A comparison of the adhesion of the calcium phosphate-titanium dioxide film with that of a pure calcium phosphate coating obtained by a similar route suggests the involvement of a chemical component in the binding.

Calcium Phosphates↗

PubMed1996