On The Panel Unit Root Tests Using Nonlinear Instrumental Variables

This paper re-examines the panel unit root tests proposed by Chang (2002). She establishes asymptotic independence of the t-statistics when integrable functions of lagged dependent variable are used as instruments even if the original series are cross sectionally dependent. She claims that her non-linear instrumental variable (NIV) panel unit root test is valid under general error cross correlations for any N (the cross section dimension) as T (the time dimension of the panel) tends to infinity. These results are largely due to her particular choice of the error correlation matrix which results in weak cross section dependence. Also, the asymptotic independence property of the t- statistics disappears when Chang's modified instruments are used. Using a common factor model with a sizeable degree of cross section correlations, we show that Chang's NIV panel unit root test suffers from gross size distortions, even when N is small relative to T

LM Unit Root Test with Panel Data: A Test Robust To Structural Changes

This paper proposes an LM test for the unit root hypothesis using panel data. The LM statistic based on the pooled likelihood function is obtained by standardizing the average of the LM statistic for individual time series. Under the null hypothesis, the statistic follows the standard normal distribution in the limit as N, T goes to infinity as long as N/T approaches any finite number, regardless of whether structural breaks are present. According to the Monte Carlo simulation results, the LM test is robust to the presence of structural breaks, and is more powerful than the popular test proposed by Im, Pesaran and Shin (1997) in the benchmark case where no structural breaks are involved.

AN INVESTIGATION INTO THE GAP BETWEEN KOREAN UNIVERSITY STUDENTS’ GRAMMATICAL AWARENESS AND PERCEPTION

Despite the consistent emphasis on grammar instruction in English classrooms in South Korea, studies regarding grammar instruction have not yet been extensively conducted. The present study aims to discover the gap between learners’ grammatical awareness and their perception of major grammatical items. A total of 60 EFL learners from two local universities in South Korea participated in the study and were divided into two groups, a high-level and a low-level group. A set of tests was utilized to examine learners’ grammatical awareness and their perception of six major grammatical items—tense, prepositions, articles, voices, morphology, and vocabulary. The results demonstrated that there was a significant difference in the scores of tense, article, and voice for grammatical awareness between the high-level and the low-level group. Also, both groups scored high for the category of voice while they received low scores for vocabulary and morphology. In addition, they showed a significant difference in the scores for the perceived difficulty of articles and voice. The high-level group perceived voice as the most difficult, whereas the low-level group perceived articles as the most difficult. These findings demonstrate a gap between the learners’ grammar awareness and perception and highlight a need to design an individualized curriculum for the effectiveness of teaching as well as self-initiated studying

Medium Resolution Near-Infrared Spectra of the Host Galaxies of Nearby Quasars

We present medium resolution near-infrared host galaxy spectra of low redshift quasars, PG 0844 + 349 (z=0.064), PG 1226 + 023 (z=0.158), and PG 1426+015 (z=0.086). The observations were done by using the Infrared Camera and Spectrograph (IRCS) at the Subaru 8.2 m telescope. The full width at half maximum of the point spread function was about 0.3 arcsec by operations of an adaptive optics system, which can effectively resolve the quasar spectra from the host galaxy spectra. We spent up to several hours per target and developed data reduction methods to reduce the systematic noises of the telluric emissions and absorptions. From the obtained spectra, we identified absorption features of Mg I (1.503 um), Si I (1.589 um) and CO (6-3) (1.619 um), and measured the velocity dispersions of PG 0844 + 349 to be 132+/-110 km s-1 and PG 1426 + 015 to be 264+/-215 km s-1. By using an M_BH-sigma relation of elliptical galaxies, we derived the black hole (BH) mass of PG 0844+349, log(M_BH/M_SUN) = 7.7+/-5.5 and PG 1426+015, log(M_BH/M_SUN) = 9.0+/-7.5. These values are consistent with the BH mass values from broad emission lines with an assumption of a virial factor of 5.5.Comment: 16 pages, 5 figure

Compact and cross-linked nanoparticles: nano- platform for highly stable, versatile conjugation and its bio-application

Department of Chemical EngineeringIron oxide nanoparticles (IONPs) have been investigated enormously in bio-application field including MRI contrast image, cancer cell targeting, biological sensing, and drug delivery. All these bio applicable IONPs require highly monodisperse size, biocompatibility, and long term colloidal stability in aqueous media. The synthesis of high quality IONPs was reported in the previous study. However, these uniform sizes of IONPs are constructed with hydrophobic ligand because they are synthesized in oil phase. In addition, IONPs for bio application, the surface modification step is essential. There are two main surface modification methods, ligand exchange and encapsulation with amphiphilic polymers, have been employed to produce water dispersible and biocompatible IONPs. Although encapsulation process is easy, rapid, and reproducible, there are limitations of poor purification of polymer micelle structure and increase in hydrodynamic diameter size. In this research, to overcome these limitations, ligand exchange with random copolymer which was synthesized by RAFT polymerization was used to synthesize highly compact and robust water dispersible IONPs. After 12 nm of IONPs were ligand exchanged with optimized ligand, these were maintained compact HD size about ~15??4 nm with high yield and reproducibility. Although their colloidal stability was established, functionalization of IONPs and stability in further reactions to conjugate bio molecules were required. To achieve these requirements, ???cross-linking??? using various length of diamine was investigated in this research. Cross-linking reaction proceeded by EDC coupling of diamine and carboxyl group of IONPs surface ligand. From this process, highly enhanced colloidal stability of IONPs and functionalization of amine group were expected. To confirm the cross-linked nanoparticles (CLNPs), XPS spectra and visualization with TEM analysis were performed. CLNPs enhanced stability was compared with PEG dominant ligand (IONPs-PEG) and acid included ligand (IONPs-AA) composed IONPs by broad range of pHs, NaCl solution, temperature, purification effects and ???click chemistry??? condition. These were evaluated by changes of each conditions of IONPs sizes with DLS analysis. Furthermore, as available functionalized amines of CLNPs were observed by RITC conjugation, tried to conjugate two different bio molecules. One is mannose carbohydrate conjugation was proceeded and confirmed with HR-MAS analysis and FT-IR. Also, MR relaxivity was measured by concanavalin A (Con A) mannose selective binding lectin to confirm conjugated mannose was retained their property. The other approach was folic acid conjugation. With folic acid conjugated CLNPs (CLNPs-FA), in vitro test was performed. HeLa cell which have lots of folate receptor on their surface was used to evaluate CLNPs-FA targeting ability. The result of targeting was observed with Prussian blue staining of HeLa cell. Through this research, compact and robust ligand and cross-linking conditions were optimized and confirmed various tool. At the same time, amine functionalization of IONPs were accomplished with facile method simultaneously. This ligand and cross-linking methods have great potential to be applied to the other nanoparticles for improvements of various bio applications.ope

MCM8-9 complex promotes resection of double-strand break ends by MRE11-RAD50-NBS1 complex.

MCM8-9 complex is required for homologous recombination (HR)-mediated repair of double-strand breaks (DSBs). Here we report that MCM8-9 is required for DNA resection by MRN (MRE11-RAD50-NBS1) at DSBs to generate ssDNA. MCM8-9 interacts with MRN and is required for the nuclease activity and stable association of MRN with DSBs. The ATPase motifs of MCM8-9 are required for recruitment of MRE11 to foci of DNA damage. Homozygous deletion of the MCM9 found in various cancers sensitizes a cancer cell line to interstrand-crosslinking (ICL) agents. A cancer-derived point mutation or an SNP on MCM8 associated with premature ovarian failure (POF) diminishes the functional activity of MCM8. Therefore, the MCM8-9 complex facilitates DNA resection by the MRN complex during HR repair, genetic or epigenetic inactivation of MCM8 or MCM9 are seen in human cancers, and genetic inactivation of MCM8 may be the basis of a POF syndrome

Nanocomposite hydrogel actuators hybridized with various dimensional nanomaterials for stimuli responsiveness enhancement

Hydrogel actuators, that convert external energy, such as pH, light, heat, magnetic field, and ion strength, into mechanical motion, have been utilized in sensors, artificial muscles, and soft robotics. For a practicality of the hydrogel actuators in a wide range of fields, an establishment of robust mechanical properties and rapid response are required. Several solutions have been proposed, for example, setting porous and anisotropy structures to hydrogels with nanocomposite materials to improve the response speed and deformation efficiency. In this review paper, we focused on hydrogel actuators including various nanocomposite by categorizing the dimensional aspects of additive materials. Moreover, we described the role of diverse additive materials in terms of the improvement of mechanical property and deformation efficiency of the hydrogel actuators. We assumed that this review will provide a beneficial guidance for strategies of developing nanocomposite hydrogel actuators and outlooks for the future research directions.11Ysciescopu

Reducing Surface Clutter in Cloud Profiling Radar Data

An algorithm has been devised to reduce ground clutter in the data products of the CloudSat Cloud Profiling Radar (CPR), which is a nadir-looking radar instrument, in orbit around the Earth, that measures power backscattered by clouds as a function of distance from the instrument. Ground clutter contaminates the CPR data in the lowest 1 km of the atmospheric profile, heretofore making it impossible to use CPR data to satisfy the scientific interest in studying clouds and light rainfall at low altitude. The algorithm is based partly on the fact that the CloudSat orbit is such that the geodetic altitude of the CPR varies continuously over a range of approximately 25 km. As the geodetic altitude changes, the radar timing parameters are changed at intervals defined by flight software in order to keep the troposphere inside a data-collection time window. However, within each interval, the surface of the Earth continuously "scans through" (that is, it moves across) a few range bins of the data time window. For each radar profile, only few samples [one for every range-bin increment ((Delta)r = 240 m)] of the surface-clutter signature are available around the range bin in which the peak of surface return is observed, but samples in consecutive radar profiles are offset slightly (by amounts much less than (Delta)r) with respect to each other according to the relative change in geodetic altitude. As a consequence, in a case in which the surface area under examination is homogenous (e.g., an ocean surface), a sequence of consecutive radar profiles of the surface in that area contains samples of the surface response with range resolution (Delta)p much finer than the range-bin increment ((Delta)p 10 dB and a reduction of the contaminated altitude over ocean from about 1 km to about 0.5 km (over the ocean). The algorithm has been embedded in CloudSat L1B processing as of Release 04 (July 2007), and the estimated flat surface clutter is removed in L2B-GEOPROF product from the observed profile of reflectivity (see CloudSat product documentation for details and performance at http://www.cloudsat.cira.colostate.edu/ dataSpecs.php?prodid=1)