Reversible ferromagnetism study in un-doped ZnO thin films.

Room temperature ferromagnetism in pure ZnO thin films prepared by spin-coating method was observed. X-ray photoelectron spectroscopy and inductively coupled plasma-mass spectrometry showed no or extremely little presence of impurities, which were unlikely to be responsible for the large magnetization moment observed. In order to study the origin of ferromagnetism, ZnO thin films were rapidly annealed in N2 and O2 ambient in a repetitive way. Electrical and magnetic performance after each annealing was measured. It is found that ferromagnetism is diminished and re-appeared, in accordance with the decrease and increase of conductivity. Cathodoluminescence spectra show evidence of reversible variation of oxygen vacancy defect in the annealing process. These results provide strong evidence that oxygen vacancies play a significant role in inducing ferromagnetism in ZnO thin films.

Dynamic organization of splicing factors in adenovirus-infected cells.

Adenovirus infection affects the nuclear distribution of host splicing factors. Late phase-infected cells contain discrete clusters of small nuclear ribonucleoproteins (snRNPs) that are separate from centers containing the viral 72-kilodalton DNA-binding protein (72K protein). In the present study, we demonstrate that these snRNP clusters also contain splicing factors from the SR protein family. We show that a previously described monoclonal antibody, 3C5, detects SR proteins. Furthermore, we demonstrate that late region 3 transcription occurs at a maximal rate in infected cultures in which greater than 90% of the cells contain the snRNP clusters, indicating that such cells are actively transcribing their late genes. During the onset of the late phase, the intranuclear distribution of splicing factors is very different from that seen after the late phase is established. When late viral transcription commences, cells with snRNP clusters are less prevalent than in cultures that are maintaining maximum levels of late transcription. Instead, a cell type which shows snRNPs, concentrated in foci that also contain the viral 72K DNA-binding protein is detected. This cell type disappears from cultures by 18 to 20 h after a high-multiplicity infection. These results suggest a dynamic organization of splicing factors in infected cells that can be correlated to the status of viral gene expression. Our work also provides an explanation for the differing results that have been published concerning the organization of splicing factors in the adenovirus-infected cell nucleus (L. F. Jiménez-García and D. L. Spector, Cell 73:47-59, 1993). During the present study we observed that a monoclonal antibody against the SC-35 protein, which was used by Jiménez-García and Spector to study the localization of the SC-35 splicing factor in adenovirus-infected cells, cross-reacts with the adenovirus 72K DNA-binding protein and is thus unsuitable for this type of study.