2,575 research outputs found
Vibrational spectroscopy and microwave dielectric properties of AY2Si3O10 (A=Sr, Ba) ceramics for 5G applications
AY2Si3O10 (AāÆ=āÆSr, Ba) trisilicate ceramics were synthesized by traditional high temperature solid state reaction method. X-ray diffraction patterns and Rietveld refinement revealed that AY2Si3O10 (AāÆ=āÆSr, Ba) ceramics belonged to triclinic and monoclinic crystal systems with PÄ« and P21/m space groups, respectively. The vibrational modes of [SiO4] tetrahedra, [YO6] octahedra and [(Sr/Ba)O8] polyhedra were analyzed by Raman spectroscopy. The infrared spectroscopy fitting analysis was used to determine intrinsic dielectric properties. Excellent microwave dielectric properties were measured for SrY2Si3O10 and BaY2Si3O10 with ÉrāÆ=āÆ9.3, QfāÆ=āÆ64100āÆGHz, ĻfāÆ=āÆā31āÆppm/Ā°C and ÉrāÆ=āÆ9.5, QfāÆ=āÆ65600āÆGHz, ĻfāÆ=āÆā28āÆppm/Ā°C, respectively. Both trisilicate ceramics are considered potential candidates for 5G and mm wave technology, provided Ļf can be further tuned
Retraction note: endoperoxide formation by an Ī±-ketoglutarate-dependent mononuclear non-haem iron enzyme
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Comparative Transcriptional Profiling and Preliminary Study on Heterosis Mechanism of Super-Hybrid Rice
Heterosis is a biological phenomenon whereby the offspring from two parents show improved and superior performance than either inbred parental lines. Hybrid rice is one of the most successful apotheoses in crops utilizing heterosis. Transcriptional profiling of F1 super-hybrid rice Liangyou-2186 and its parents by serial analysis of gene expression (SAGE) revealed 1183 differentially expressed genes (DGs), among which DGs were found significantly enriched in pathways such as photosynthesis and carbon-fixation, and most of the key genes involved in the carbon-fixation pathway exhibited up-regulated expression in F1 hybrid rice. Moreover, increased catabolic activity of corresponding enzymes and photosynthetic efficiency were also detected, which combined to indicate that carbon fixation is enhanced in F1 hybrid, and might probably be associated with the yield vigor and heterosis in super-hybrid rice. By correlating DGs with yield-related quantitative trait loci (QTL), a potential relationship between differential gene expression and phenotypic changes was also found. In addition, a regulatory network involving circadian-rhythms and light signaling pathways was also found, as previously reported in Arabidopsis, which suggest that such a network might also be related with heterosis in hybrid rice. Altogether, the present study provides another view for understanding the molecular mechanism underlying heterosis in rice
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HDAC9 is implicated in atherosclerotic aortic calcification and affects vascular smooth muscle cell phenotype.
Aortic calcification is an important independent predictor of future cardiovascular events. We performed a genome-wide association meta-analysis to determine SNPs associated with the extent of abdominal aortic calcification (nā=ā9,417) or descending thoracic aortic calcification (nā=ā8,422). Two genetic loci, HDAC9 and RAP1GAP, were associated with abdominal aortic calcification at a genome-wide level (Pā<ā5.0āĆā10-8). No SNPs were associated with thoracic aortic calcification at the genome-wide threshold. Increased expression of HDAC9 in human aortic smooth muscle cells promoted calcification and reduced contractility, while inhibition of HDAC9 in human aortic smooth muscle cells inhibited calcification and enhanced cell contractility. In matrix Gla protein-deficient mice, a model of human vascular calcification, mice lacking HDAC9 had a 40% reduction in aortic calcification and improved survival. This translational genomic study identifies the first genetic risk locus associated with calcification of the abdominal aorta and describes a previously unknown role for HDAC9 in the development of vascular calcification
Allelic shift in cis-elements of the transcription factor RAP2.12 underlies adaptation associated with humidity in Arabidopsis thaliana
Populations of widespread species are usually geographically distributed through contrasting stresses, but underlying genetic mechanisms controlling this adaptation remain largely unknown. Here, we show that in Arabidopsis thaliana, allelic changes in the cis-regulatory elements, WT box and W box, in the promoter of a key transcription factor associated with oxygen sensing, RELATED TO AP 2.12 (RAP2.12), are responsible for differentially regulating tolerance to drought and flooding. These two cis-elements are regulated by different transcription factors that downstream of RAP2.12 results in differential accumulation of hypoxia-responsive transcripts. The evolution from one cis-element haplotype to the other is associated with the colonization of humid environments from arid habitats. This gene thus promotes both drought and flooding adaptation via an adaptive mechanism that diversifies its regulation through noncoding alleles
Carbon concentration declines with decay class in tropical forest woody debris
Carbon stored in woody debris is a key carbon pool in forest ecosystems. The most widely-used method to convert woody debris volume to carbon is by first multiplying field-measured volume with wood density to obtain necromass, and then assuming that a fixed proportion (often 50%) of the necromass is carbon. However, this crucial assumption is rarely tested directly, especially in the tropics. The aim of this study is to verify the field carbon concentration values of living trees and woody debris in two distinct tropical forests in Taiwan. Wood from living trees and woody debris across five decay classes was sampled to measure density and carbon concentrations. We found that both wood density and carbon concentration (carbon mass/total mass) declined significantly with the decay class of the wood. Mean (Ā±SE) carbon concentration values for living trees were 44.6 Ā± 0.1%, while for decay classes one to five they were respectively 41.1 Ā± 1.4%, 41.4 Ā± 1.0%, 37.7 Ā± 1.3%, 30.5 Ā± 2.0%, and 19.6 Ā± 2.2%. Total necromass carbon stock was low, only 3.33 Ā± 0.55 Mg C haā1 in the windward forest (Lanjenchi) and 4.65 Ā± 1.63 Mg C haā1 in the lowland forest (Nanjenshan). Applying the conventional 50% necromass carbon fraction value would cause a substantial overestimate of the carbon stocks in woody debris of between 17% and 36%, or about 1 Mg of carbon per hectare. The decline in carbon concentration and the increase of variances in the heavily decayed class suggest that in high-diversity tropical forests there are diverse decomposition trajectories and that assuming a fixed carbon fraction across woody pieces is not justified. Our work reveals the need to consider site-specific and decay class-specific carbon concentrations in order to accurately estimate carbon stocks and fluxes in forest ecosystems. If the marked decline in carbon content with necromass decay is typical of tropical forests, the dead wood carbon pool in the biome needs revision and is likely to be overestimate
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