Color Magnitude Relation and Morphology of Low-Redshift ULIRGs in SDSS

We present color-magnitude and morphological analysis of 54 low-redshift ULIRGs, a subset of the IRAS 1Jy sample (Kim & Sanders, 1998), in the SDSS. The ULIRGs are on average 1 magnitude brighter in M0.1r than the SDSS galaxies within the same redshift range. The majority of the ULIRGs (~87%) have the colors typical of the blue cloud, and only 4 sources (~7%) are located in the red sequence. While ULIRGs are popularly thought to be precursors to a QSO phase, we find few (~6%) in the "green valley" where the majority of the X-ray and IR selected AGNs are found, and none of which harbors an AGN. For the 14 previously spectroscopic identified AGNs (~28%), we perform PSF subtractions and find that on average the central point sources contribute less than one third to the total luminosity, and that their high optical luminosities and overall blue colors are apparently the result of star formation activity of the host galaxies. Visual inspection of the SDSS images reveals a wide range of disturbed morphologies. A detailed morphology analysis using Gini and M20 coefficients shows that slightly less than one half (~42% in g band) of the ULIRGs are located in the region where most local mergers are found. The heterogeneous distribution of ULIRGs in the G-M20 space is qualitatively consistent with the results found by numerical simulations of disk-disk mergers. Our study also shows that the measured morphological parameters are systematically affected by the SNR and thus the merging galaxies can appear at various regions in the G-M20 space. In general, our results reinforce the view that ULIRGs contain young stellar populations and are mergers in progress. Our study provides a uniform comparison sample for studying ULIRGs at higher redshifts such as Spitzer mid-IR selected ULIRGs at z=1~2 and submm galaxies.Comment: 42 pages, 11 figures, ApJ accepte

Detecting Slow Wave Sleep Using a Single EEG Signal Channel

Background: In addition to the cost and complexity of processing multiple signal channels, manual sleep staging is also tedious, time consuming, and error-prone. The aim of this paper is to propose an automatic slow wave sleep (SWS) detection method that uses only one channel of the electroencephalography (EEG) signal. New Method: The proposed approach distinguishes itself from previous automatic sleep staging methods by using three specially designed feature groups. The first feature group characterizes the waveform pattern of the EEG signal. The remaining two feature groups are developed to resolve the difficulties caused by interpersonal EEG signal differences. Results and comparison with existing methods: The proposed approach was tested with 1,003 subjects, and the SWS detection results show kappa coefficient at 0.66, an accuracy level of 0.973, a sensitivity score of 0.644 and a positive predictive value of 0.709. By excluding sleep apnea patients and persons whose age is older than 55, the SWS detection results improved to kappa coefficient, 0.76; accuracy, 0.963; sensitivity, 0.758; and positive predictive value, 0.812. Conclusions: With newly developed signal features, this study proposed and tested a single-channel EEG-based SWS detection method. The effectiveness of the proposed approach was demonstrated by applying it to detect the SWS of 1003 subjects. Our test results show that a low SWS ratio and sleep apnea can degrade the performance of SWS detection. The results also show that a large and accurately staged sleep dataset is of great importance when developing automatic sleep staging methods

Giant negative magnetoresistance of spin polarons in magnetic semiconductors–chromium-doped Ti2O3 thin films

Epitaxial Cr-doped Ti2O3 films show giant negative magnetoresistance up to –365% at 2 K. The resistivity of the doped samples follows the behavior expected of spin (magnetic) polarons at low temperature. Namely, rho= rho0 exp(T0/T)p, where p = 0.5 in zero field. A large applied field quenches the spin polarons and p is reduced to 0.25 expected for lattice polarons. The formation of spin polarons is an indication of strong exchange coupling between the magnetic ions and holes in the system

Synthesis and characterization of caffeic acid and dihydrocaffeic acid derivatives as antifungal agents

Invasive fungal infection, a major cause of morbidity and mortality in immuno-compromised hosts, is of importance and is significantly increasing in incidence in recent years. Although there are a number of antifungal agents currently available, they are associated with various limitations. Being inhibitors of fungal cell wall biosynthesis, the class of echinocandins is characterized by outstanding safety profiles and great potential in combination antifungal therapy, but they fall short in oral bioavailability. A discovery of peptidomimetic analogues of echinocandin B, with potential inhibitory activity against 1,3-β-D-glucan synthase (an enzyme essential for the biosynthesis of fungal cell walls), was initiated by our research group. A series of structurally related derivatives (chlorogenic, quinic, caffeic and dihydrocaffeic acid derivatives) were later designed to mimic the backbone of echinocandins. Further studies have been carried out on optimization of synthesis and modifications of a caffeic acid derivative. Due to the instability problems of previously reported compounds, a new molecule, a dihydrocaffeic acid derivative, has been designed and synthesized. It was found that adopting a few optimized procedures can not only improve the yield and purity of the caffeic acid derivatives, but also save a lot of time in synthesis

The impacts of dividend-smoothing risk, institutional investors and investor behaviour on equity pricing

Asset pricing theory analyses the value of financial claims to uncertain future payments. In the case of a stock the financial claims are its future dividends. Prices move in response to changes in discount rates, information on future dividends reflecting profitability or changes in behavioural bias. 1. Is dividend smoothing a priced risk factor? (discount rates) 2. Do firms use smooth dividends to signal? (profitability) 3. What behaviour leads to mispricing? (behavioural bias) I attempt to answer the first question by examining whether dividend smoothing can explain returns. More specifically, can it replace the small and value risk factors? I add a dividend smoothing factor to the CAPM and find that the smoothing factor had some explanatory power for the US stocks but not for Chinese stocks. However, this explanatory power is limited to non-large firms and does not perform well as the Fama-French three-factor model. I attempt to answer the second question by examining the circumstances in which a smoothed dividend can convey information. Whether a smooth dividend acts as a signalling mechanism depends on its relationship with institutional investors: the type of institution, the direction of the relationship and the severity of the principal-agent problem. In the US, institutional monitors control the principal-agent problem and require dividend smoothing in exchange. In China, where the principal-agent problem is less pronounced, institutional monitors replace dividend smoothing to mitigate the minority-controlling shareholder problem. Dividend smoothing is not used as a signalling device in either case. In addition, managers in both countries pay smoothed dividends for their benefit when the colluders’ institutional holdings are high. I attempt to answer the third question by identifying the sources of momentum. I wonder whether both overreaction and underreaction to information could cause a momentum effect. I establish different momentum strategies in China only, where short selling is not allowed. I find that Chinese investors underreact to bad news and overreact to good news. Among them, institutional investors intensify their overreaction to good news in bad times

Studying dawn-dusk asymmetries of Mercury's magnetotail using MHD-EPIC simulations

MESSENGER has observed a lot of dawn-dusk asymmetries in Mercury's magnetotail, such as the asymmetries of the cross-tail current sheet thickness and the occurrence of flux ropes, dipolarization events and energetic electron injections. In order to obtain a global pictures of Mercury's magnetotail dynamics and the relationship between these asymmetries, we perform global simulations with the magnetohydrodynamics with embedded particle-in-cell (MHD-EPIC) model, where Mercury's magnetotail region is covered by a PIC code. Our simulations show that the dawnside current sheet is thicker, the plasma density is larger, and the electron pressure is higher than the duskside. Under a strong IMF driver, the simulated reconnection sites prefer the dawnside. We also found the dipolarization events and the planetward electron jets are moving dawnward while they are moving towards the planet, so that almost all dipolarization events and high-speed plasma flows concentrate in the dawn sector. The simulation results are consistent with MESSENGER observations