Electronic band structures of Ge1−xSnx semiconductors: A first-principles density functional theory study

[[abstract]]We conduct first-principles total-energy density functional calculations to study the band structures in Ge 1− x Sn x infrared semiconductor alloys. The norm-conserving optimized pseudopotentials of Ge and Sn have been constructed for electronic structure calculations. The composition-bandgap relationships in Ge 1−x Sn x lattices are evaluated by a detailed comparison of structural models and their electronic band structures. The critical Sn composition related to the transition from indirect- to direct-gap in Ge 1−x Sn x alloys is estimated to be as low as x∼ 0.016 determined from the parametric fit. Our results show that the crossover Sn concentration occurs at a lower critical Sn concentration than the values predicted from the absorption measurements. However, early results indicate that the reliability of the critical Sn concentration from such measurements is hard to establish, since the indirect gap absorption is much weaker than the direct gap absorption. We find that the direct band gap decreases exponentially with the Sn composition over the range 0 0.375, in very good agreement with the theoretical observed behavior [D. W. Jenkins and J. D. Dow, Phys. Rev. B 36, 7994, 1987]. For homonuclear and heteronuclear complexes of Ge 1−x Sn x alloys, the indirect band gap at L-pointis is found to decrease homonuclear Ge-Ge bonds or increase homonuclear Sn-Sn bonds as a result of the reduced L valley. All findings agree with previously reported experimental and theoretical results. The analysis suggests that the top of valence band exhibits the localization of bond charge and the bottom of the conduction band is composed of the Ge 4s4p and/or Sn 5s5p atomic orbits.[[booktype]]紙本[[booktype]]電子

Isospin Effect on the Process of Multifragmentation and Dissipation at Intermediate Energy Heavy Ion Collisions

In the simulation of intermediate energy heavy ion collisions by using the isospin dependent quantum molecular dynamics, the isospin effect on the process of multifragmentation and dissipation has been studied. It is found that the multiplicity of intermediate mass fragments $N_{imf}$ for the neutron-poor colliding system is always larger than that for the neutron-rich system, while the quadrupole of single particle momentum distribution $Q_{zz}$ for the neutron-poor colliding system is smaller than that of the neutron-rich system for all projectile-target combinations studied at the beam energies from about 50MeV/nucleon to 150MeV/nucleon. Since $Q_{zz}$ depends strongly on isospin dependence of in-medium nucleon-nucleon cross section and weakly on symmetry potential at the above beam energies, it may serve as a good probe to extract the information on the in-medium nucleon-nucleon cross section. The correlation between the multiplicity $N_{imf}$ of intermediate mass fragments and the total numer of charged particles $N_c$ has the behavior similar to $Q_{zz}$, which can be used as a complementary probe to the in-medium nucleon-nucleon cross section.Comment: 18 pages, 9 figure

Begonia wuzhishanensis (sect. Diploclinium, Begoniaceae), a new species from Hainan Island, China

Background: Hainan is the largest island of the Indo-Burma Biodiversity Hotspot and has the best preserved and most extensive tropical forests in China. A recent study on distribution of endangered species in China identifies southern Hainan as one of eight hotspots for plant conservation in the country. In continuation of our studies of Asian Begonia, we report the discovery of an attractive undescribed species, B. wuzhishanensis C.-I Peng, X.H. Jin & S.M.Ku, from Hainan Island. Results: Living plant of the new species, Begonia wuzhishanensis, was collected in 2009 and cultivated in the experimental greenhouse for morphological and cytological studies. It flowered consecutively in 2012 and 2013 in the experimental greenhouse, Academia Sinica. It was assigned to the large, heterogeneous sect. Diploclinium. The chromosome number of this new species was determined to be 2n = 26. Conclusions: A careful study of literature, herbarium specimens and living plants, both in the wild and in cultivation, support the recognition of the new species Begonia wuzhishanensis, which is described in this paper. Begonia wuzhishanensis is currently known only from Fanyang, Wuzhishan Mountain in the center of the island. A line drawing, color plate, and a distribution map are provided to aid in identification

Excessive Dpp signaling induces cardial apoptosis through dTAK1 and dJNK during late embryogenesis of Drosophila

<p>Abstract</p> <p>Background</p> <p>To identify genes involved in the heart development of <it>Drosophila</it>, we found that embryos lacking <it>raw </it>function exhibited cardial phenotypes. <it>raw </it>was initially identified as a dorsal open group gene. The dorsal open phenotype was demonstrated to be resulted from the aberrant expression of <it>decapentaplegic </it>(<it>dpp</it>), a member of the tumor growth factor beta (TGF-β), signaling pathway. Despite the role of <it>dpp </it>in pattering cardioblasts during early embryogenesis of <it>Drosophila </it>have been demonstrated, how mutation in <it>raw </it>and/or excessive <it>dpp </it>signaling involves in the differentiating heart of <it>Drosophila </it>has not been fully elaborated at late stages.</p> <p>Results</p> <p>We show that <it>raw </it>mutation produced a mild overspecification of cardial cells at stage 14, but these overproduced cells were mostly eliminated in late mutant embryos due to apoptosis. Aberrant <it>dpp </it>signaling is likely to contribute to the cardial phenotype found in <it>raw </it>mutants, because expression of <it>dpp </it>or constitutively activated <it>thickven </it>(<it>tkv^CA</it>), the type I receptor of Dpp, induced a <it>raw</it>-like phenotype. Additionally, we show that <it>dpp </it>induced non-autonomous apoptosis through TGFβ activated kinase 1 (<it>TAK1</it>), because mis-expression of a dominant negative form of <it>Drosophila TAK1 </it>(<it>dTAK1^DN</it>) was able to suppress cell death in <it>raw </it>mutants or embryos overexpressing <it>dpp</it>. Importantly, we demonstrated that <it>dpp </it>induce its own expression through <it>dTAK1</it>, which also leads to the hyperactivation of <it>Drosophila </it>JNK (DJNK). The hyperactivated DJNK was attributed to be the cause of Dpp/DTAK1-induced apoptosis because overexpression of a dominant negative DJNK, <it>basket </it>(<it>bsk^DN</it>), suppressed cell death induced by Dpp or DTAK1. Moreover, targeted overexpression of the anti-apoptotic P35 protein, or a dominant negative proapoptotic P53 (P53^DN) protein blocked Dpp/DTAK1-induced apoptosis, and rescued heart cells under the <it>raw </it>mutation background.</p> <p>Conclusions</p> <p>We find that ectopic Dpp led to DJNK-dependent cardial apoptosis through the non-canonical TGF-β pathway during late embryogenesis of <it>Drosophila</it>. This certainly will increase our understanding of the pathogenesis of cardiomyopathy, because haemodynamic overload can up-regulate TGF-β and death of cardiomyocytes is observed in virtually every myocardial disease. Thus, our study may provide possible medical intervention for human cardiomyopathy.</p

Taiwan Oscillation Network

The Taiwan Oscillation Network (TON) is a ground-based network to measure solar intensity oscillations to study the internal structure of the Sun. K-line full-disk images of 1000 pixels diameter are taken at a rate of one image per minute. Such data would provide information onp-modes withl as high as 1000. The TON will consist of six identical telescope systems at proper longitudes around the world. Three telescope systems have been installed at Teide Observatory (Tenerife), Huairou Solar Observing Station (near Beijing), and Big Bear Solar Observatory (California). The telescopes at these three sites have been taking data simultaneously since October of 1994. Anl – v diagram derived from 512 images is included to show the quality of the data

The nucleolar protein NIFK promotes cancer progression via CK1α/β-catenin in metastasis and Ki-67-dependent cell proliferation.

Nucleolar protein interacting with the FHA domain of pKi-67 (NIFK) is a Ki-67-interacting protein. However, its precise function in cancer remains largely uninvestigated. Here we show the clinical significance and metastatic mechanism of NIFK in lung cancer. NIFK expression is clinically associated with poor prognosis and metastasis. Furthermore, NIFK enhances Ki-67-dependent proliferation, and promotes migration, invasion in vitro and metastasis in vivo via downregulation of casein kinase 1α (CK1α), a suppressor of pro-metastatic TCF4/β-catenin signaling. Inversely, CK1α is upregulated upon NIFK knockdown. The silencing of CK1α expression in NIFK-silenced cells restores TCF4/β-catenin transcriptional activity, cell migration, and metastasis. Furthermore, RUNX1 is identified as a transcription factor of CSNK1A1 (CK1α) that is negatively regulated by NIFK. Our results demonstrate the prognostic value of NIFK, and suggest that NIFK is required for lung cancer progression via the RUNX1-dependent CK1α repression, which activates TCF4/β-catenin signaling in metastasis and the Ki-67-dependent regulation in cell proliferation