Phonon anomaly in BaFe2As2

The detailed optical properties of BaFe2As2 have been determined over a wide frequency range above and below the structural and magnetic transition at T_N = 138 K. A prominent in-plane infrared-active mode is observed at 253 cm^{-1} (31.4 meV) at 295 K. The frequency of this vibration shifts discontinuously at T_N; for T < T_N the frequency of this mode displays almost no temperature dependence, yet it nearly doubles in intensity. This anomalous behavior appears to be a consequence of orbital ordering in the Fe-As layers.Comment: 4 pages, 3 figures and one table (minor revisions

Extraction of low molecular weight RNA from Citrus trifolita tissues for microRNA Northern blotting and reverse transcriptase polymerase chain reaction (RTPCR)

The study of microRNA (miRNA), a component of low molecular weight RNA (LMW RNA), has received increasing attention in recent years. A critical prerequisite in miRNA studies is acquisition of high quality LMW RNA. LMW RNA is generally obtained from total RNA or from total nucleic acids solutions. Most traditional methods for LMW RNA isolation involve many steps and chemical reagents which upon degradation may negatively affect results. We employed a simple and quick method involving trizol for total RNA extraction from citrus tissues, then generation of LMW RNA using 4M LiCl, which have been successfully utilized in studies in our laboratory. Compared with traditional methods, this method is less expensive and produced high RNA yields while avoiding the use of phenol or other toxic reagents. In addition, the entire procedure can be completed within 4 hours with many samples being processed simultaneously. Therefore, this is a practical and efficient method for LMW RNA extraction from woody fruit crops containing high levels of polysaccharide and polyphenolics. Using the extracted LMW RNA, miRNAs were successfully detected and characterized by reverse transcriptase polymerase chain reaction (RT-PCR) and Northern blotting.Keywords: Citrus, low molecular weight RNA, trizol reagent, 4 M LiCl, microRNA

Luminous Infrared Galaxies in the Local Universe

We study the morphology and star formation properties of 159 local luminous infrared galaxy (LIRG) using multi-color images from Data Release 2 (DR2) of the Sloan Digital Sky Survey (SDSS). The LIRGs are selected from a cross-correlation analysis between the IRAS survey and SDSS. They are all brighter than 15.9 mag in the r-band and below redshift ~ 0.1, and so can be reliably classified morphologically. We find that the fractions of interacting/merging and spiral galaxies are ~ 48% and ~ 40% respectively. Our results complement and confirm the decline (increase) in the fraction of spiral (interacting/merging) galaxies from z ~1 to z ~ 0.1, as found by Melbourne, Koo & Le Floc'h (2005). About 75% of spiral galaxies in the local LIRGs are barred, indicating that bars may play an important role in triggering star formation rates > 20 M_{sun}/yr in the local universe. Compared with high redshift LIRGs, local LIRGs have lower specific star formation rates, smaller cold gas fractions and a narrower range of stellar masses. Local LIRGs appear to be either merging galaxies forming intermediate mass ellipticals or spiral galaxies undergoing high star formation activities regulated by bars.Comment: 22 pages, 5 figures, accepted for publication in ApJ, title changed, typos corrected,major revisions following referee's comments,updated reference

Electronic Structure of KFe2_2Se2_2 from First Principles Calculations

Electronic structure and magnetic properties for iron-selenide KFe$_2$Se$_2$ are studied by first-principles calculations. The ground state is stripe-like antiferromagnetic with calculated 2.26 $\mu_B$ magnetic moment on Fe atoms; and the $J_1$, $J_2$ coupling strengths are calculated to be 0.038 eV and 0.029 eV. The states around $E_F$ are dominated by the Fe-3d orbitals which hybridize noticeably to the Se-4p orbitals. While the band structure of KFe$_2$Se$_2$ is similar to a heavily electron-doped BaFe$_2$As$_2$ or FeSe system, the Fermi surface of KFe$_2$Se$_2$ is much closer to \fs11 system since the electron sheets around $M$ is symmetric with respect to $x$-$y$ exchange. These features, as well as the absence of Fermi surface nesting, suggest that the parental KFe$_2$Se$_2$ could be regarded as an electron over-doped 11 system with possible local moment magnetism.Comment: accepted by Chinese Physics Letter, to appear as Chinese Physics Letter, Vol 28, page 057402 (2011

Cloning and expression of cell wall acid invertase gene fragment from poinsettia (Euphorbia pulcherrima wild.)

A fragment of invertase gene containing catalytic sites of cysteine was cloned from poinsettia (Euphorbia pulcherrima wild.) by using the polymerase chain reaction (PCR) method. The length of the fragment was 521 bp, encoding 173 amino acids and containing a part of open reading frames, but no intron. It had a high homology to previously cloned cell wall acid invertase genes in other plants by sequence comparison, so it could be speculated that the fragment belongs to putative cell-wall acidinvertase gene sequence of poinsettia (termed as EpCWINV, GenBank no. EU274662). Gene expression analyses in different organs including roots, stems, leaves, flowers among others and during different growth periods of leaves by semi-quantitative reverse transcriptase-polymerase chain reaction (RTPCR) method and real-time quantitative PCR approach revealed the highest level of expression in roots, the lower in stems and intermediate in leaves and flowers, as well as a continuous rising level in leaves and a continuous declining level in petioles during the developmental stages of the leaves