Academia Sinica

About: Academia Sinica is a facility organization based out in Taipei, Taiwan. It is known for research contribution in the topics: Population & Gene. The organization has 52086 authors who have published 65998 publications receiving 1728114 citations. The organization is also known as: Central Research Academy.

The Chloroplast Genome of Phalaenopsis aphrodite (Orchidaceae): Comparative Analysis of Evolutionary Rate with that of Grasses and Its Phylogenetic Implications

Abstract: Whether the Amborella/Amborella-Nymphaeales or the grass lineage diverged first within the angiosperms has recently been debated. Central to this issue has been focused on the artifacts that might result from sampling only grasses within the monocots. We therefore sequenced the entire chloroplast genome (cpDNA) of Phalaenopsis aphrodite, Taiwan moth orchid. The cpDNA is a circular molecule of 148,964 bp with a comparatively short single-copy region (11,543 bp) due to the unusual loss and truncation/scattered deletion of certain ndh subunits. An open reading frame, orf91, located in the complementary strand of the rrn23 was reported for the first time. A comparison of nucleotide substitutions between P. aphrodite and the grasses indicates that only the plastid expression genes have a strong positive correlation between nonsynonymous (K a ) and synonymous (f s ) substitutions per site, providing evidence for a generation time effect, mainly across these genes. Among the intron-containing protein-coding genes of the sampled monocots, the K s of the genes are significantly correlated to transitional substitutions of their introns. We compiled a concatenated 61 protein-coding gene alignment for the available 20 cpDNAs of vascular plants and analyzed the data set using Bayesian inference, maximum parsimony, and neighbor-joining (NJ) methods. The analyses yielded robust support for the Amborella/Amborella-Nymphaeales-basal hypothesis and for the orchid and grasses together being a monophyletic group nested within the remaining angiosperms. However, the NJ analysis using K a , the first two codon positions, or amino acid sequences, respectively, supports the monocots-basal hypothesis. We demonstrated that these conflicting angiosperm phylogenies are most probably linked to the transitional sites at all codon positions, especially at the third one where the strong base-composition bias and saturation effect take place.

Quantum dot monolayer sensitized ZnO nanowire-array photoelectrodes: true efficiency for water splitting.

Abstract: Increasing demand for clean energy has motivated considerable effort to exploit the properties of various materials in photovoltaics and related solar-harvesting devices. Splitting of water by sunlight to generate hydrogen is one of the forms of energy production with the most potential. Metal oxides such as TiO2, ZnO, and WO3 with various morphologies have been investigated for use in splitting water. However, most of these metal oxides have large band gaps, which limit light absorption in the visible region and overall efficiency. To reduce the band gaps of nanostructured metal oxides, doping and utilization of transition metals, carbon, or nitrogen have been investigated. One possibility is the use of semiconductor nanocrystals, known as quantum dots (QDs), as an alternative to photosensitive dyes. Quantum dots generally offer various significant advantages over dyes. It was recently established that QDs generate multiple electron– hole pairs per photon, improving device efficiency. Quantum dot sensitized nanostructures are widely studied for use in solar cells. However, little work has been done on metal oxide and semiconductor QD-based composite structures for use in water-splitting nanodevices. To elucidate this fundamental issue, we examined a combination of CdTe QDs and ZnO nanowires for splitting water photoelectrochemically (Scheme 1). One-dimensional nanostructures offer the additional potential advantage of improved charge transport over zero-dimensional nanostructures such as nanocrystals. Additionally, the typical electron mobility in ZnO is 10–100 times higher than that in TiO2, so the electrical resistance is lower and the electron-transfer efficiency higher. However, since the overall water-splitting reaction is tough, sacrificial reagents are commonly adopted to evaluate the photocatalytic activity for water splitting. When the photocatalytic reaction is carried out in an aqueous solution that contains a reductant, electron donors, or hole scavengers such as sulfide ions or selenium ions, photogenerated holes irreversibly oxidize the reductant rather than the water. Employment of CdTe QDs in water splitting system has major advantages. CdTe with a more favorable conduction band energy (ECB= 1.0 V vs. NHE) can inject electrons into ZnO faster than CdSe (ECB= 0.6 V vs. NHE). In addition, monolayer deposition of CdTe QDs on the surface of ZnO nanowires would further improve the stability in electrochemical reaction, by avoiding anodic decomposition/corrosion of CdTe and thus enhancing the overall watersplitting performance. During the photoirradiation of CdTe, two reactions can be expected to dominate after initial charge separation [Eqs. (1) and (2)].

GaN Metalens for Pixel-Level Full-Color Routing at Visible Light

Abstract: Metasurface-based components are known to be one of the promising candidates for developing flat optical systems. However, their low working efficiency highly limits the use of such flat components for feasible applications. Although the introduction of the metallic mirror has been demonstrated to successfully enhance the efficiency, it is still somehow limited for imaging and sensing applications because they are only available for devices operating in a reflection fashion. Here, we demonstrate three individual GaN-based metalenses working in a transmission window with extremely high operation efficiency at visible light (87%, 91.6%, and 50.6% for blue, green, and red light, respectively). For the proof of concept, a multiplex color router with dielectric metalens, which is capable of guiding individual primary colors into different spatial positions, is experimentally verified based on the design of out-of-plane focusing metalens. Our approach with low-cost, semiconductor fabrication compatibility and h...

Curcumin induces apoptosis in immortalized NIH 3T3 and malignant cancer cell lines

Abstract: Curcumin, which is a widely used dietary pigment and spice, has been demonstrated to be an effective inhibitor of tumor promotion in mouse skin carcinogenesis. We report that curcumin induces cell shrinkage, chromatin condensation, and DNA fragmentation, characteristics of apoptosis, in immortalized mouse embryo fibroblast NIH 3T3 erb B2 oncogene-transformed NIH 3T3, mouse sarcoma S180, human colon cancer cell HT-29, human kidney cancer cell 293, and human hepatocellular carcinoma Hep G2 cells, but not in primary culture of mouse embryonic fibroblast C3H 10T1/2, rat embryonic fibroblast, and human foreskin fibroblast cells in a concentration- and time-dependent manner. Many cellular and biochemical effects of curcumin in mouse fibroblast cells have been reported, such as inhibition of protein kinase C (PKC) activity induced by phorbol 12-myristate 13-acetate treatment, inhibition of tyrosine protein kinase activity, and inhibition of arachidonic acid (AA) metabolism. Treatment of NIH 3T3 cells with the PKC inhibitor staurosporine, the tyrosine kinase inhibitor herbimycin A, and the AA metabolism inhibitor quinacrine induces apoptotic cell death. These results suggest that, in some immortalized and transformed cells, blocking the cellular signal transduction might trigger the induction of apoptosis.