Biomedical subjects

D K Ferry

Publications and source records attributed to D K Ferry.

4 recordsLinked to original sources

PubMed2004

Einselection in action: decoherence and pointer states in open quantum dots.

Recent work on the role of decoherence has suggested that the decay of quantum effects is governed by a discrete set of pointer states, which affect the quantum to classical correspondence. We show that the conductance oscillations exhibited by open quantum dots are governed by a discrete set of stable quantum states which have the properties of the pointer states, and which are closely related to trapped classical orbits in the open dot.

Journal Article↗

PubMed2003

Signatures of dynamical tunneling in semiclassical quantum dots.

We study transport in large, and strongly open, quantum dots, which might typically be viewed as lying well within the semiclassical regime. The low-temperature magnetoresistance of these structures exhibits regular fluctuations, with just a small number of dominant frequency components, indicative of the presence of dynamical tunneling into regular orbits. Support for these ideas is provided by the results of numerical simulations, which reveal wave function scarring by classically inaccessible orbits, which is found to persist even in the presence of a moderately disordered dot potential. Our results suggest that dynamical tunneling may play a more generic role in transport through mesoscopic structures than has thus far been appreciated.

Journal Article↗

PubMed2000

Regulation of HMG-CoA reductase degradation requires the P-type ATPase Cod1p/Spf1p.

The integral ER membrane protein HMG-CoA reductase (HMGR) is a key enzyme of the mevalonate pathway from which sterols and other essential molecules are produced. HMGR degradation occurs in the ER and is regulated by mevalonate-derived signals. Little is known about the mechanisms responsible for regulating HMGR degradation. The yeast Hmg2p isozyme of HMGR undergoes regulated degradation in a manner very similar to mammalian HMGR, allowing us to isolate mutants deficient in regulating Hmg2p stability. We call these mutants cod mutants for the control of HMG-CoA reductase degradation. With this screen, we have identified the first gene of this class, COD1, which encodes a P-type ATPase and is identical to SPF1. Our data suggested that Cod1p is a calcium transporter required for regulating Hmg2p degradation. This role for Cod1p is distinctly different from that of the well-characterized Ca(2+) P-type ATPase Pmr1p which is neither required for Hmg2p degradation nor its control. The identification of Cod1p is especially intriguing in light of the role Ca(2+) plays in the regulated degradation of mammalian HMGR.

ATP-Binding Cassette Transporters↗

PubMed1983

Synchronous and asynchronous systems of threshold elements.

The role of synchronism in systems of threshold elements (such as neural networks) is examined. Some important differences between synchronous and asynchronous systems are outlined. In particular, important restrictions on limit cycles are found in asynchronous systems along with multi-frequency oscillations which do not appear in synchronous systems. The possible role of deterministic chaos in these systems is discussed.

Animals↗