764 research outputs found
Role of mitochondria in Parkinson disease
The cause of the selective degeneration of nigrostriatal neurons in Parkinson disease (PD) has remained largely unknown. Exceptions include rare missense mutations in the alpha-synuclein gene on chromosome 4, a potentially pathogenic mutation affecting the ubiquitin pathway, and mutations in the parkin gene on chromosome 6. However, unlike classical PD, the latter syndrome is not associated with the formation of typical Lewy bodies. In contrast, a biochemical defect of complex I of the mitochondrial respiratory chain has been described in a relatively large group of confirmed PD cases. Recent cybrid studies indicate that the complex I defect in PD has a genetic cause and that it may arise from mutations in the mitochondrial DNA, Sequence analysis of the mitochondrial genome supports the view that mitochondrial point mutations are involved in PD pathogenesis. However, although mitochondria function as regulators in several known forms of cell death, their exact involvement in PD has remained unresolved. This is of relevance because classical apoptosis does not appear to play a major role in the degeneration of the parkinsonian nigra
Purification of quantum trajectories
We prove that the quantum trajectory of repeated perfect measurement on a
finite quantum system either asymptotically purifies, or hits upon a family of
`dark' subspaces, where the time evolution is unitary.Comment: 10 page
Information Transfer Implies State Collapse
We attempt to clarify certain puzzles concerning state collapse and
decoherence. In open quantum systems decoherence is shown to be a necessary
consequence of the transfer of information to the outside; we prove an upper
bound for the amount of coherence which can survive such a transfer. We claim
that in large closed systems decoherence has never been observed, but we will
show that it is usually harmless to assume its occurrence. An independent
postulate of state collapse over and above Schroedinger's equation and the
probability interpretation of quantum states, is shown to be redundant.Comment: 13 page
- …