Abstract: The invention relates to a wall flow filter for removing particulate matter from the exhaust of internal combustion engines, comprising a wall flow filter substrate having a length L, and different coatings Z and F, the wall flow filter substrate being provided with channels E and A which run parallel between a first end and a second end of the wall flow filter substrate, are separated by porous walls, and form surfaces OE and OA, respectively; channels E are closed at the second end, and channels A are closed at the first end; coating Z is disposed in the porous walls and/or on surfaces OA, but not on surfaces OE, and contains palladium and/or rhodium and a cerium/zirconium mixed oxide; coating F is disposed mainly on surfaces OE, but not on surfaces OA, and comprises a membrane and no precious metal. The wall flow filter is characterized in that the mass ratio of coating Z to coating F ranges from 0.1 to 25.

Abstract: A method and arrangements for determining an at least approximately circular contacting surface is disclosed. The primary object of finding a simple way of objectively determining the contacting surface of a deformable medium on a plane surface with high accuracy and at a low technical expense is met according to the invention in that a film waveguide is used as a plane surface. An incoherent, parallel, homogeneous bundle of light whose width widens one-dimensionally is coupled into this film waveguide and the decoupled light is fed to a photoreceiver array for recording one-dimensional intensity distributions. An evaluating unit generates a difference curve from a normal curve without contacting medium and from a measurement curve with contacting medium and the exact diameter of the contacting surface is determined from the distance of two associated extremes of the difference curve.