Abstract: A new electrochemical sensor for determining hydrogen peroxide concentration having a mixed-valence metal oxide of MxOy deposited on an electrode surface thereof is disclosed, wherein M is a transition metal and has two or more than two valences. MxOy, for example, is M3O4 where M is Mn, Fe, Co or Pb, Tb4O7 or Pr6O11. Further, this invention also discloses an electrochemical sensor for determining a concentration of a hydrogen peroxide precursor, wherein a catalyst is immobilized in the matrix or on the surface of the mixed-valence metal oxide on the electrode. In a typical biochemical system, the catalyst can be a glucose oxidase and blood glucose is catalyzed to form hydrogen peroxide, so that the concentration of blood glucose is determined.

Abstract: A tri-leaflet heart valve includes an annular valve base with an inner surface forming an orifice through which blood flows from the upstream side to the downstream side. Three protruding hinges, each with concave sockets on opposite sides, are formed on the inner surface. Each hinge has a downstream face and an upstream face connected by a ridge. Three leaflets are respectively arranged between adjacent hinges. Each leaflet has round pivots on both sides that rest inside the concave sockets, allowing the leaflets to freely rotate in the annular valve base. When the leaflets are subject to a positive pressure from the blood flow, the leaflets are pushed open and allow a central flow. When the leaflets are subject to a negative pressure, the leaflets are closed to occlude the blood flow.