Optical emission from a charge-tunable quantum ring

Quantum dots or rings are artificial nanometre-sized clusters that confine electrons in all three directions. They can be fabricated in a semiconductor system by embedding an island of low-bandgap material in a sea of material with a higher bandgap. Quantum dots are often referred to as artificial atoms because, when filled sequentially with electrons, the charging energies are pronounced for particular electron numbers; this is analogous to Hund's rules in atomic physics. But semiconductors also have a valence band with strong optical transitions to the conduction band. These transitions are the basis for the application of quantum dots as laser emitters, storage devices and fluorescence markers. Here we report how the optical emission (photoluminescence) of a single quantum ring changes as electrons are added one-by-one. We find that the emission energy changes abruptly whenever an electron is added to the artificial atom, and that the sizes of the jumps reveal a shell structure.     

Erythropoietic response to isomeres of triiodothyronine

Zusammenfassung Verabreichung vond-, wie auch vonl-Triiodothyrosin erzeugt eine ähnliche Vermehrung der Erythropoiesis in nephroektomierten Ratten, wie bei der Messung der Radioeiseninkorporation durch Erythrozyten (18 h nach Injektion von radioaktivem Eisencitrat). Es ergab sich weiter, dassd- undl-Thyrosin, im Unterschied zu Erythropoieten, die reticulozytose Eisenassimilation in vitro vermehrte. Danach scheinen verschiedene Mechanismen bei der Stimulation der Erythropoiesis durch Erythropoieten und Triiodothyronin im Spiele zu sein.     

Individual carboxypeptidase D domains have both redundant and unique functions in Drosophila development and behavior

Metallocarboxypeptidase D (CPD) functions in protein and peptide processing. The Drosophila CPD svr gene undergoes alternative splicing, producing forms containing 1–3 active or inactive CP domains. To investigate the function of the various CP domains, we created transgenic flies expressing specific forms of CPD in the embryonic-lethal svr ^PG33 mutant. All constructs containing an active CP domain rescued the lethality with varying degrees, and full viability required inactive CP domain-3. Transgenic flies overexpressing active CP domain-1 or -2 were similar to each other and to the viable svr mutants, with pointed wing shape, enhanced ethanol sensitivity, and decreased cold sensitivity. The transgenes fully compensated for a long-term memory deficit observed in the viable svr mutants. Overexpression of CP domain-1 or -2 reduced the levels of Lys/Arg-extended adipokinetic hormone intermediates. These findings suggest that CPD domains-1 and -2 have largely redundant functions in the processing of growth factors, hormones, and neuropeptides.