Biomedical subjects

J J Finley

Publications and source records attributed to J J Finley.

4 recordsLinked to original sources

PubMed2006

Optically probing spin and charge interactions in a tunable artificial molecule.

We optically probe and electrically control a single artificial molecule containing a well defined number of electrons. Charge and spin dependent interdot quantum couplings are probed optically by adding a single electron-hole pair and detecting the emission from negatively charged exciton states. Coulomb- and Pauli-blockade effects are directly observed, and tunnel coupling and electrostatic charging energies are independently measured. The interdot quantum coupling is shown to be mediated by electron tunneling. Our results are in excellent accord with calculations that provide a complete picture of negative excitons and few-electron states in quantum dot molecules.

Journal Article↗

PubMed2005

Direct observation of controlled coupling in an individual quantum dot molecule.

We report the direct observation of quantum coupling in individual quantum dot molecules and its manipulation using static electric fields. A pronounced anticrossing of different excitonic transitions is observed as the electric field is tuned. A comparison of our experimental results with theory shows that the observed anticrossing occurs between excitons with predominant spatially direct and indirect character and reveals a field driven transition of the nature of the molecular ground state exciton wave function. Finally, the interdot quantum coupling strength is deduced optically and its dependence on the interdot separation is calculated.

Journal Article↗

PubMed2000

Inverted electron-hole alignment in InAs-GaAs self-assembled quantum dots.

New information on the electron-hole wave functions in InAs-GaAs self-assembled quantum dots is deduced from Stark effect spectroscopy. Most unexpectedly it is shown that the hole is localized towards the top of the dot, above the electron, an alignment that is inverted relative to the predictions of all recent calculations. We are able to obtain new information on the structure and composition of buried quantum dots from modeling of the data. We also demonstrate that the excited state transitions arise from lateral quantization and that tuning through the inhomogeneous distribution of dot energies can be achieved by variation of electric field.

Journal Article↗

PubMed1987

Biochemical and histochemical characterization of cultured rat and hamster pancreatic ducts.

Pancreatic duct fragments were isolated from rat and hamster pancreas and were cultured in an agarose matrix for up to 8 weeks (rat) or 20 weeks (hamster). The fragments consisted predominantly of duct epithelium, lesser numbers of stromal and atrophied acinar cells, and small numbers of islet cells. Hamster ducts averaged 3 micrograms protein per duct while rat ducts averaged 1 microgram, and the protein:DNA ratio of both types of ducts was less than that of whole pancreas. Estimated average duct yields of 6% (hamster) and 1% (rat) were based on the protein content of the ducts. Duct viability was shown by the incorporation of 3H-thymidine and 3H-leucine into bulk DNA and protein and by autoradiography. gamma-Glutamyl transferase and (Na + K)-ATPase specific activities were slightly elevated while amylase was depressed in the ducts when compared with whole pancreas in both species. gamma-Glutamyl transferase was localized histochemically in both duct epithelium and in surviving acinar tissue, as seen in vivo. Amylase was shown by immunohistochemistry to be present within duct lumina and in atrophied acini and their lumina. Alkaline phosphatase and Mg-ATPase specific activities were elevated in the hamster, but reduced in the rat, when compared with whole pancreas. Hamster alkaline phosphatase and Mg-ATPase were localized by histochemistry to the duct stroma, where these enzymes are not detected in vivo. Carbonic anhydrase was found in the duct epithelium of both species, as in vivo, as well as in the duct stroma, unlike in vivo. Acid glycosaminoglycans, as revealed by alcian blue staining, were found at the apical surfaces and in the lumina of both kinds of ducts. Glutathione-S-transferase and glucose-6-phosphate dehydrogenase were elevated in rat ducts, but not in hamster ducts. The polypeptide compositions of cultured ducts, freshly isolated pancreatic islets, and whole pancreas were compared by one-dimensional sodium dodecyl sulfate polyacrylamide gradient gel electrophoresis. No duct-specific polypeptides were observed; the ducts were characterized mainly by the reduction or absence of polypeptides, including some zymogens, seen in whole pancreas.

Alkaline Phosphatase↗