Analysis of differentially expressed genes in malignant biliary strictures.

Microarray data were collected from bile duct samples from subjects with malignant biliary strictures by endoscopic retrograde cholangiopancreatography to screen for key genes associated with this disease. A predicted interaction network was constructed for these genes to interpret their functions. The gene expression dataset GSE34166 (10 samples: 6 malignant and 4 benign control samples) was downloaded from the Gene Expression Omnibus database. R package scripts were used to process the data and screen for differentially expressed genes. Genes identified were uploaded to the analysis tool String 8.3 to generate a gene interaction network. A hub gene was identified by calculating the node degree. The interaction network of the hub gene with other genes in the human genome was constructed and screened (score >0.9), and pathway-enrichment analysis was performed to elucidate the hub gene function. In total, 377 differentially expressed genes were identified and a network comprising 209 pairs of interactions was constructed. The most critical hub gene was identified as GSTA1, and a GSTA1-based interaction network was constructed consisting of 25 genes (containing the differentially expressed gene GSTA3). The cytochrome P450 (CYP450)-metabolic pathway displayed the most significant enrichment. Additionally, 4 transcription factors and their binding sites were also identified. In conclusion, we have identified the differentially expressed genes GSTA1 (a hub gene) and GSTA3, which may cause abnormal gene expression and tumorigenesis through CYP450-metabolic pathways. The transcription factors and their binding sites in the promoter of the hub gene provide potential directions for future drug design.

Room-temperature ferromagnetism of Cu-doped ZnO films probed by soft X-ray magnetic circular dichroism.

We report direct evidence of room-temperature ferromagnetic ordering in O-deficient ZnO:Cu films by using soft x-ray magnetic circular dichroism and x-ray absorption. Our measurements have revealed unambiguously two distinct features of Cu atoms associated with (i) magnetically ordered Cu ions present only in the oxygen-deficient samples and (ii) magnetically disordered regular Cu2+ ions present in all the samples. We find that a sufficient amount of both oxygen vacancies (V(O)) and Cu impurities is essential to the observed ferromagnetism, and a non-negligible portion of Cu impurities is uninvolved in the magnetic order. Based on first-principles calculations, we propose a microscopic "indirect double-exchange" model, in which alignments of localized large moments of Cu in the vicinity of the V(O) are mediated by the large-sized vacancy orbitals.

Cationic-vacancy-induced room-temperature ferromagnetism in transparent, conducting anatase Ti1-xTaxO2 (x~0.05) thin films.

We report room-temperature ferromagnetism (FM) in highly conducting, transparent anatase Ti(1-x)Ta(x)O(2) (x∼0.05) thin films grown by pulsed laser deposition on LaAlO(3) substrates. Rutherford backscattering spectrometry (RBS), X-ray diffraction, proton-induced X-ray emission, X-ray absorption spectroscopy (XAS) and time-of-flight secondary-ion mass spectrometry indicated negligible magnetic contaminants in the films. The presence of FM with concomitant large carrier densities was determined by a combination of superconducting quantum interference device magnetometry, electrical transport measurements, soft X-ray magnetic circular dichroism (SXMCD), XAS and optical magnetic circular dichroism, and was supported by first-principles calculations. SXMCD and XAS measurements revealed a 90 per cent contribution to FM from the Ti ions, and a 10 per cent contribution from the O ions. RBS/channelling measurements show complete Ta substitution in the Ti sites, though carrier activation was only 50 per cent at 5 per cent Ta concentration, implying compensation by cationic defects. The role of the Ti vacancy (V(Ti)) and Ti(3+) was studied via XAS and X-ray photoemission spectroscopy, respectively. It was found that, in films with strong FM, the V(Ti) signal was strong while the Ti(3+) signal was absent. We propose (in the absence of any obvious exchange mechanisms) that the localized magnetic moments, V(Ti) sites, are ferromagnetically ordered by itinerant carriers. Cationic-defect-induced magnetism is an alternative route to FM in wide-band-gap semiconducting oxides without any magnetic elements.