658 research outputs found
Observation of Wannier-Stark localization at the surface of BaTiO films by photoemission
Observation of Bloch oscillations and Wannier-Stark localization of charge
carriers is typically impossible in single-crystals, because an electric field
higher than the breakdown voltage is required. In BaTiO however, high
intrinsic electric fields are present due to its ferroelectric properties. With
angle-resolved photoemission we directly probe the Wannier-Stark localized
surface states of the BaTiO film-vacuum interface and show that this effect
extends to thin SrTiO overlayers. The electrons are found to be localized
along the in-plane polarization direction of the BaTiO film
Real-Time Non-Rigid Surface Detection
On-line diagnostics of power system components is an important area since it allows the diagnostics to be performed at regular intervals during the normal operation of the components. This combined with reliability centered maintenance could lead to reduced customer outages. In this thesis the on-line diagnostic methods for medium voltage cross-linked polyethylene (XLPE) cables are investigated based on Time Domain Reflectometry (TDR). Degradation of XLPE insulated power cables by water-trees (WT) is a primary cause of failure of these cables. The detection of WT and information about the severity of the degradation can be obtained with off-line measurements using dielectric spectroscopy. In many situations only a limited part of the cable may be degraded by the WT. In such a situation a method for localization of this WT section would be desirable. The developed high frequency measurements superimposed on HV system is presented. It was used to measure the propagation constant of the WT aged cables as a function of the applied HV. This was done in order to study the diagnostic criteria, which could be used for on-line TDR diagnostics of WT aged cables. A physically based dielectric model of WT was developed in order to explain qualitatively and quantitatively the permittivity and loss of WT at different frequencies and voltages. The sensors applicable for the on-line TDR were investigated in terms of sensitivity and bandwidth. High frequency models were built and the simulation results in frequency and time domains were verified by measurements. The developed on-line TDR systems are presented. Their applicability to detect water penetration under the cable sheath and localize the broken screen wires was investigated during the measurements in laboratory environment. The results of field measurements with on-line TDR are presented. Variations due to load cycling of the cable were observed, where an increase in the cable temperature cause an increase of the pulse propagation velocity in the cable. The temperature dependent wave propagation in the cable is investigated and explained by modeling.QC 20100709</p
PrĂ©paration chez le Bovin et titrage dâun sĂ©rum contre la maladie de CarrĂ©. Etude comparĂ©e de son pouvoir protecteur
Recherches expérimentales sur la maladie de Teschen (méningo~encéphalo~myélite enzootique du porc)
Verge Jean, Pilet Ed., BĂŒck G., Quesnel J.-J. Recherches expĂ©rimentales sur la maladie de Teschen (mĂ©ningo-encĂ©phalo-myĂ©lite enzootique du Porc). In: Bulletin de l'AcadĂ©mie VĂ©tĂ©rinaire de France tome 104 n°7, 1951. pp. 373-377
Exploring atomic-scale lateral forces in the attractive regime: a case study on graphite (0001)
Cataloged from PDF version of article.A non-contact atomic force microscopy-based method has been used to map the static lateral forces exerted on an atomically sharp Pt/Ir probe tip by a graphite surface. With measurements carried out at low temperatures and in the attractive regime, where the atomic sharpness of the tip can be maintained over extended time periods, the method allows the quantification and directional analysis of lateral forces with piconewton and picometer resolution as a function of both the in-plane tip position and the vertical tip-sample distance, without limitations due to a finite contact area or to stick-slip-related sudden jumps of tip apex atoms. After reviewing the measurement principle, the data obtained in this case study are utilized to illustrate the unique insight that the method offers. In particular, the local lateral forces that are expected to determine frictional resistance in the attractive regime are found to depend linearly on the normal force for small tip-sample distances
EVALUATION OF THE NEWLY FORMED BONE IN IRRADIATED AREAS BY ADDITION OF MESENCHYMAL STEM CELLS TO THE ASSOCIATION OF BIPHASIC CALCIUM PHOSPHATE AND TOTAL BONE MARROW
Oral Communication presented at the ";Forum des Jeunes Chercheurs";, Brest (France) 2011
Computational model combined with in vitro experiments to analyse mechanotransduction during mesenchymal stem cell adhesion.
The shape that stem cells reach at the end of adhesion
process influences their differentiation. Rearrangement of
cytoskeleton and modification of intracellular tension may
activate mechanotransduction pathways controlling cell
commitment. In the present study, the mechanical signals
involved in cell adhesion were computed in in vitro stem
cells of different shapes using a single cell model, the
so-called Cytoskeleton Divided Medium (CDM) model.
In the CDM model, the filamentous cytoskeleton and
nucleoskeleton networks were represented as a mechanical
system of multiple tensile and compressive interactions
between the nodes of a divided medium. The results showed
that intracellular tonus, focal adhesion forces as well as
nuclear deformation increased with cell spreading. The
cell model was also implemented to simulate the adhesion
process of a cell that spreads on protein-coated substrate by
emitting filopodia and creating new distant focal adhesion
points. As a result, the cell model predicted cytoskeleton
reorganisation and reinforcement during cell spreading.
The present model quantitatively computed the evolution
of certain elements of mechanotransduction and may be a
powerful tool for understanding cell mechanobiology and
designing biomaterials with specific surface properties to
control cell adhesion and differentiation
- âŠ