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A process for treating natural gas or other methane-rich gas to remove excess nitrogen. The invention relies on two-stage membrane separation, using methane-selective membranes for the first stage and nitrogen-selective membranes for the second stage. The process enables the nitrogen content of the

A process for treating natural gas or other methane-rich gas to remove excess nitrogen. The invention relies on two-stage membrane separation, using methane-selective membranes for the first stage and nitrogen-selective membranes for the second stage. The process enables the nitrogen content of the gas to be substantially reduced, without requiring the membranes to be operated at very low temperatures.

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A process for treating natural gas or other methane-rich gas to remove excess nitrogen. The invention relies on two-stage membrane separation, using methane-selective membranes for the first stage and nitrogen-selective membranes for the second stage. The process enables the nitrogen content of the

A process for treating natural gas or other methane-rich gas to remove excess nitrogen. The invention relies on two-stage membrane separation, using methane-selective membranes for the first stage and nitrogen-selective membranes for the second stage. The process enables the nitrogen content of the gas to be substantially reduced, without requiring the membranes to be operated at very low temperatures. prises a measuring means (5-8) for measuring at least one optical characteristic of the predetermined volume, the optical characteristic varying with the size of the destroyed volume, the measuring means being connected to said control unit for controlling the supply of the tissue-destroying medium on the basis of the measured optical characteristic. surface. 19. The implantable hearing aid of claim 18 wherein said output actuator is encased within an assembly having a portion adapted for rigid insertion into a bony portion of a promontory, said assembly adapted to having an opening through which said actuating surface of said output actuator is in fluid communication with an inner ear. 20. The implantable hearing aid of claim 1 wherein said output actuator is encased within an assembly having a portion adapted for rigid insertion into a bony portion of a promontory, said assembly adapted to having an opening through which said actuating surface of said output actuator is in fluid communication with an inner ear. 21. The implantable hearing aid of claim 1 wherein said output actuator is adapted to be in mechanical communication with an auditory component of a middle ear. 22. The implantable hearing aid of claim 21 wherein said output actuator is configured for attachment to a stapes. 23. The implantable hearing aid of claim 22 comprising a series of stacked output actuators. 24. The implantable hearing aid of claim 22 wherein said first and second end caps are substantially bowed away from said planar surface. 25. The implantable hearing aid of claim 22 wherein said first and second end caps are substantially bowed towards said planar surface. 26. An implantable hearing aid for placement substantially proximate to a middle ear or an inner ear comprising: a) at least one output actuator comprising a substrate having a first and second opposing surfaces, a thickness, and a transverse size, said substrate being comprised of a material which changes in said thickness and said transverse size upon application of a voltage; b) a first end cap having a first actuating surface, said first end cap fixedly attached to a portion of a first planar surface where a change in said transverse size of said substrate produces a proportional movement in said first actuating surface in a direction orthogonal to said planar surface; c) a biocompatible material isolating at least a portion of said output actuator, wherein said output actuator is adapted to be in mechanical communication with an auditory component of a middle ear, and said output actuator is configured for attachment to a stapes; and d) a spacer adapted to be positioned between said stapes and said output actuator; said spacer comprising a flexible portion, where said flexible portion expands in size from a natural state and maintains an expanded state upon reaching body temperature, wherein said output actuator is secured within said middle ear when said spacer is in said expanded state. 27. The implantable hearing aid of claim 26 wherein said spacer comprises a superelastic alloy. 28. The implantable hearing aid of claim 26 wherein said spacer comprises a shape memory alloy. 29. The implantable hearing aid of claim 26 wherein said output actuator is adapted to be contiguous with a footplate of said stapes. 30. The implantable hearing aid of claim 29 wherein said output actuator has a prismatoid shape. 31. The implantable hearing aid of claim 26 wherein said spacer is positionable within a posterior limb and an anterior limb of said stapes and between a neck of said stapes and said output actuator. 32. The implantable hearing aid of claim 26 wherein a cylinder is placed in contact with a side of said output actuator opposite said spacer, wherein said cylinder is positioned to transmit motion of said output actuator to cochlear fluid through a hole in said footplate. 33. The implantable hearing aid of claim 22 further comprising: a) an axis along a long side of said stapes, a hole in a footplate of said stapes along said axis; and b) a portion of said output actuator located in said hole. 34. The implantable hearing aid of claim 33 further comprising a first membrane covering said hole, and said portion of said output actuator is placed into said first membrane. 35. The implantable hearing aid of claim 33 wherein