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There is disclosed a magnetic fluid medium which comprises a plurality of ferro- or ferri-magnetic particles, each of which particles has a largest dimension no greater than 100 nm, said particles having been prepared by a process which includes a step in which the particles are formed within an org

There is disclosed a magnetic fluid medium which comprises a plurality of ferro- or ferri-magnetic particles, each of which particles has a largest dimension no greater than 100 nm, said particles having been prepared by a process which includes a step in which the particles are formed within an organic macromolecular shell.

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1. A magnetic fluid medium, comprising a plurality of magnetic particles, each of said magnetic particles havinz a largest dimension no greater than about 100 nm, said plurality of magetic pticicles prepared by a process comprising the step of forming at least one of said magnetic particles within a

1. A magnetic fluid medium, comprising a plurality of magnetic particles, each of said magnetic particles havinz a largest dimension no greater than about 100 nm, said plurality of magetic pticicles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, wherein said at least one organic macromolecule is a molecule, or assembly of molecules, having a molecular weight of up to 1500 kD and wherein said at least one of said magnetic particles comprises a metal or a metal alloy. 2. The magnetic fluid medium of claim 1, wherein each of said magnetic particles has a largest dimension no greater than about 50 nm. 3. The magnetic fluid medium of claim 1, wherein each of said magnetic particles has a largest dimension no greater than about 15 nm. 4. The magnetic fluid medium of claim 1, wherein said magnetic particles vary in their largest dimension by no more than about 10%. 5. The magnetic fluid medium of claim 1, wherein said magnetic particles vary in their largest dimension by no more than about 5%. 6. The magnetic fluid medium of claim 1, wherein at least one of said magnetic particles is accommodated within the organic macromolecule within which it is formed. 7. The magnetic fluid medium of claim 1, wherein said shell of said at least one organic macromolecule has been removed thereby forming an uncoated nanoscale particle. 8. The magnetic fluid medium of claim 1, wherein said shell of said at least one organic macromolecule has been carbonized thereby providing a carbon layer surrounding a nanoscale particle core. 9. A magnetic fluid medium, comprising a plurality of magetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, wherein said at least one organic macromolecule is a protein having a cavity for accommodating a nanoscale particle therein and wherein said at least one of said magnetic particles comprises a metal or a metal alloy. 10. The magnetic fluid medium of claim 9, wherein said protein is an apoferritin. 11. The magnetic fluid medium of claim 1, wherein said magnetic particles are selected from the group consisting of ferromagnetic particles, ferrimagnetic particles, and a mixture thereof. 12. An integrated magnetic fluid seal disposed between a rotatable shaft and a bearing assembly comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepare by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, wherein said at least one organic macromolecule is a molecule, or assembly of molecules, having a molecular weight of up to 1500 kD. 13. A fluid medium for cooling of an electromagnetic device producing an external magnetic field and having an operating temperature, said medium comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, wherein said at least one organic macromolecule is a molecule, or assembly of molecules, having a molecular weight of up to 1500 kD. 14. A fluid medium for cooling of an electromagnetic device producing an external magnetic field and having an operating temperature, said medium comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 1100 nm said plurality of magnetic particles prepared by a process comprising the step of forming at least one of sai d magnetic particles within a shell of at least one organic macromolecule, wherein a concentration of said plurality of magnetic particles therein produces a bulk saturation magnetization of said medium of at least 50 Gauss. 15. The medium of claim 13 wherein the Curie temperature of said plurality of magnetic particles exceeds the average operating temperature of said electromagnetic device, and wherein said medium loses substantial magnetization at the average operating temperature. 16. The medium of claim 13 wherein the Curie temperature of said plurality of magnetic particles exceeds the maximum operating temperature of said electromagnetic device, and wherein said medium loses substantial magnetization at the maximum operating temperature. 17. A damping medium for absorbing energy, said damping medium having a predetermined viscosity controllable by an application of an external magnetic field and comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, said at least one organic macromolecule comprising a molecule, or assembly of molecules, having a molecular weight of up to 1500 kD. 18. A method for creating a unique magnetic marking on a substrate, said method comprising the steps ofproviding a magnetic medium comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule; andapplying said medium to said substrate. 19. A fluid pressure sensor comprising a magnetic fluid medium disposed in a tube having a first end and a second end, said magnetic fluid medium displaceable in response to a pressure differential between the first and the second end of said tube; said magnetic fluid medium comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, wherein said at least one organic macromolecule is a molecule, or assembly of molecules, having a molecular weight of up to 1500 kD. 20. A method for reducing distortion in a loudspeaker having a voice coil, the method comprising:providing a magnetic fluid medium comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, said at least one organic macromolecule comprising a molecule, or assembly of molecules, having a molecular weight of up to 1500 kD; anddisposing said magnetic fluid adjacent to said voice coil thereby transferring heat therefrom and providing damping therefor. 21. An optical switch comprisingat least two optical fibers having coupling of light therebetween; anda magnetic fluid medium disposed proximal to said at least two optical fibers and comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, said at least one organic macromolecule comprising a molecule, or assembly of molecules, having a molecular weight of up to 1500 kD, wherein at least one of;(a) positioning of said magnetic fluid relative to said optical fibers, or(b) at least one physical property of said magnetic fluid medium is alterable in response to an application of an external magnetic field thereto, thereby causing obstruction of said coupling of light. 22. A magneto-optical device comprising a magnetic fluid medium comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, said at least one organic macromolecule comprising a molecule, or assembly of molecules, having a molecular weight of up to 1500 kD, said magnetic fluid medium forming an ordered crystalline array in response an application of an external magnetic field thereto. 23. The magnetic fluid medium of claim 1, wherein said at least one organic macromolecule is a molecule, or assembly of molecules, having a molecular weight of up to 500 kD. 24. The magnetic fluid medium of claim 9, wherein said magnetic particles are selected from the group consisting of ferromagnetic particles, ferrimagnetic particles, and a mixture thereof. 25. The magnetic fluid medium of claim 9, wherein each of said magnetic particles has a largest dimension no greater than about 50 nm. 26. The magnetic fluid medium of claim 9, wherein said magnetic particles vary in their largest dimension by no more than about 10%. 27. The magnetic fluid medium of claim 9, wherein at least one of said magnetic particles is accommodated within the cavity of the protein. 28. The magnetic fluid medium of claim 9, wherein said shell of said at least one organic macromolecule has been removed thereby forming an uncoated nanoscale particle. 29. The magnetic fluid medium of claim 9, wherein said shell of said at least one organic macromolecule has been carbonized thereby providing a carbon layer surrounding a nanoscale particle core. 30. A magnetic fluid medium, comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, wherein said at least one organic macromolecule is a molecule, or assembly of molecules, having a molecular weight of up to 1500 kD and wherein said at least one of said magnetic particles comprises an M-type ferrite or a spinel ferrite. 31. The magnetic fluid medium of claim 30, further comprising a carrier liquid. 32. The magnetic fluid medium of claim 30, wherein said at least one organic macromolecule is a molecule, or assembly of molecules, having a molecular weight of up to 500 kD. 33. A magnetic fluid medium, comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, wherein said at least one organic macromolecule is a protein having a cavity for accommodating a nanoscale particle therein and wherein said at least one of said magnetic particles comprises an M-type ferrite or a spinel ferrite. 34. The magnetic fluid medium of claim 33, wherein said protein is an apoferritin. 35. The magnetic fluid medium of claim 33, further comprising a carrier liquid. 36. The magnetic fluid medium of claim 33, wherein each of said magnetic particles has a largest dimension no greater than about 50 nm. 37. The magnetic fluid medium of claim 33, wherein said magnetic particles vary in their largest dimension by no more than about 10%. 38. The magnetic fluid medium of claim 33, wherein at least one of said magnetic particles is accommodated within the cavity of t he protein. 39. The magnetic fluid medium of claim 33, wherein said shell of said at least one organic macromolecule has been removed thereby forming an uncoated nanoscale particle. 40. The magnetic fluid medium of claim 33, wherein said shell of said at least one organic macromolecule has been carbonized thereby providing a carbon layer surrounding a nanoscale particle core. 41. A magnetic fluid medium, comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, wherein said magnetic particles vary in their largest dimension by no more than about 10% and wherein said at least one of said magnetic particles comprises a metal or a metal alloy. 42. A method for separating solid phase from a liquid suspension, the method comprising;providing a magnetic fluid medium comprising a plurality of magnetic particles, each of said magnetic particles having a largest dimension no greater than about 100 nm, said plurality of magnetic particles prepared by a process comprising the step of forming at least one of said magnetic particles within a shell of at least one organic macromolecule, said at least one organic macromolecule comprising a molecule, or assembly of molecules, having a molecular weight of up to 1500 kD,adding said magnetic fluid medium to said suspension, andextracting said solid phase from said suspension. 43. A method of claim 42, wherein said at least one organic macromolecule is an apoferritin. 44. A method of claim 42, wherein said at least one magnetic particle comprises a metal binding ligand disposed at the surface thereof.