A Cosmology-Independent Calibration of Gamma-Ray Burst Luminosity Relations and the Hubble Diagram

An important concern in the application of gamma-ray bursts (GRBs) to cosmology is that the calibration of GRB luminosity/energy relations depends on the cosmological model, due to the lack of a sufficient low-redshift GRB sample. In this paper, we present a new method to calibrate GRB relations in a cosmology-independent way. Since objects at the same redshift should have the same luminosity distance and since the distance moduli of Type Ia supernovae (SNe Ia) obtained directly from observations are completely cosmology independent, we obtain the distance modulus of a GRB at a given redshift by interpolating from the Hubble diagram of SNe Ia. Then we calibrate seven GRB relations without assuming a particular cosmological model and construct a GRB Hubble diagram to constrain cosmological parameters. From the 42 GRBs at $1.4<z\le6.6$, we obtain $\Omega_{\rm M}=0.25_{-0.05}^{+0.04}$, $\Omega_{\Lambda}=0.75_{-0.04}^{+0.05}$ for the flat $\Lambda$CDM model, and for the dark energy model with a constant equation of state $w_0=-1.05_{-0.40}^{+0.27}$, which is consistent with the concordance model in a 1-$\sigma$ confidence region.Comment: 7 pages, 3 figures, 1 table, now matches the editorially revised version; accepted for publication in ApJ (vol 685)

Influence of Grassland Management on Carbon Allocation in a Semiarid Temperate Steppe

Grazing lands in North China are often excessively grazed and widely degraded, while hay-making lands appear to be in relatively good condition due to grazing exclusion, but they are facing a continuous loss of nutrients in the harvested biomass. In semiarid grasslands, plant productivity and community composition are significantly altered by grazing and haying. Grazing mostly leads to negative effects on aboveground productivity, however root biomass seems to increase with moderate grazing (Gao et al. 2009; Derner et al. 2006), although responses can vary. Aboveground biomass removal can increase C3 grass dominance and productivity (Hofer and Bragg 1981). Grazing exclusion is a valuable mechanism of sequestering soil C (He 2008). However, grazing can change C allocation patterns and affect the amount of C entering the soil. Here we examine the potential effects of common management practices (exclusion with fencing, grazing and hay-making) on semiarid grasslands above- and below-ground C pools. The primary objective of this study was to evaluate the potential of grazing exclusion and annual last-summer haying in previous grazing lands on the storage of C in semiarid grasslands of northern China

Optical effects of spin currents in semiconductors

A spin current has novel linear and second-order nonlinear optical effects due to its symmetry properties. With the symmetry analysis and the eight-band microscopic calculation we have systematically investigated the interaction between a spin current and a polarized light beam (or the "photon spin current") in direct-gap semiconductors. This interaction is rooted in the intrinsic spin-orbit coupling in valence bands and does not rely on the Rashba or Dresselhaus effect. The light-spin current interaction results in an optical birefringence effect of the spin current. The symmetry analysis indicates that in a semiconductor with inversion symmetry, the linear birefringence effect vanishes and only the circular birefringence effect exists. The circular birefringence effect is similar to the Faraday rotation in magneto-optics but involves no net magnetization nor breaking the time-reversal symmetry. Moreover, a spin current can induce the second-order nonlinear optical processes due to the inversion-symmetry breaking. These findings form a basis of measuring a pure spin current where and when it flows with the standard optical spectroscopy, which may provide a toolbox to explore a wealth of physics connecting the spintronics and photonics.Comment: 16 pages, 7 fig

Phase Change Observed in Ultrathin Ba0.5Sr0.5TiO3 Films by in-situ Resonant Photoemission Spectroscopy

Epitaxial Ba0.5Sr0.5TiO3 thin films were prepared on Nb-doped SrTiO3 (100)substrates by the pulsed laser deposition technique, and were studied by measuring the Ti 2p - 3d resonant photoemission spectra in the valence-band region as a function of film thickness, both at room temperature and low temperature. Our results demonstrated an abrupt variation in the spectral structures between 2.8 nm (~7 monolayers) and 2.0 nm (~5 monolayers) Ba0.5Sr0.5TiO3 films, suggesting that there exists a critical thickness for phase change in the range of 2.0 nm to 2.8 nm. This may be ascribed mainly to the intrinsic size effects.Comment: 13 pages, 4 figure

Puzzles in BB physics

I discuss some puzzles observed in exclusive $B$ meson decays, concentrating on the large difference between the direct CP asymmetries in the $B^0\to \pi^\mp K^\pm$ and $B^\pm\to \pi^0 K^\pm$ modes, the large $B^0\to\pi^0\pi^0$ branching ratio, and the large deviation of the mixing-induced CP asymmetries in the $b\to sq\bar q$ penguins from those in the $b\to c\bar c s$ trees.Comment: 6 pages, 1 figure, talk presented at the 9th Workshop on High Energy Physics Phenomenology, Bhubaneswar, Orissa, India, Jan. 3-14, 2006; reference adde

Time course of EEG activities in continuous tracking task: a pilot study

Motor learning is crucial to surgical skills enhancement, but its neural mechanism has been investigated only using some simple tasks with limited motor involvement. This study aimed to gain more understanding of the neural dynamics during motor learning by investigating the time course of electroencephalogram (EEG) activities in the continuous tracking task that involves more motor components. One participant performed 16 trials of the continuous tracking task on Day1 and Day2 respectively. The 16-channel EEG signals were recorded and analyzed in both the resting and active states. Results showed that the tracking performance improved from Day1 to Day2. Regarding the EEG, it was found that the relative amplitude in the individual alpha band (IAB) decreased locally over primary motor cortex from the resting state to the active state on both days, and this reduction was more focused on the left primary motor cortex on Day2 compared to Day1. Moreover, in the active state the alpha coherence between central and frontal areas also significantly increased from Day1 to Day2. Time course of alpha activities may explain the tracking performance enhancement from Day1 to Day2. Future work will include more participants to extend the validity of current results.published_or_final_versio

Barium isotopic composition of the mantle: Constraints from carbonatites

To investigate the behaviour of Ba isotopes during carbonatite petrogenesis and to explore the possibility of using carbonatites to constrain the Ba isotopic composition of the mantle, we report high-precision Ba isotopic analyses of: (1) carbonatites and associated silicate rocks from the only active carbonatite volcano, Oldoinyo Lengai, Tanzania, and (2) Archean to Cenozoic carbonatites from Canada, East Africa, Germany and Greenland. Carbonatites and associated phonolites and nephelinites from Oldoinyo Lengai have similar δ137/134 Ba values that range from +0.01 to +0.03‰, indicating that Ba isotope fractionation during carbonatite petrogenesis is negligible. The limited variation in δ137/134 Ba values from −0.03 to +0.09‰ for most carbonatite samples suggests that their mantle sources have a relatively homogeneous Ba isotopic composition. Based on the carbonatites investigated in this work, the average δ137/134 Ba value of their mantle sources is estimated to be +0.04 ± 0.06‰ (2SD, n = 16), which is similar to the average value of +0.05 ± 0.06‰ for mid-ocean ridge basalts. The lower δ137/134 Ba value of −0.08‰ in a Canadian sample and higher δ137/134 Ba values of +0.14‰ and +0.23‰ in two Greenland samples suggest local mantle isotopic heterogeneity that may reflect the incorporation of recycled crustal materials in their sources

Health-related quality of life in patients treated with Continuous Ambulatory Peritoneal Dialysis and Automated Peritoneal Dialysis in Singapore

OBJECTIVE: This study aimed to compare the health-related quality of life (HRQOL) in patients with end-stage renal disease (ESRD) treated with continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis (APD) in Singapore. METHODS: The data used in this study were from two cross-sectional surveys of ESRD patients. HRQOL was assessed using the Kidney Disease Quality of Life (KDQOL) instrument. Socio-demographic characteristics and clinical data were collected. The physical component summary (PCS) and mental component summary (MCS) scores, kidney disease component summary (KDCS) score and its three scales (symptoms, effects, burden), and one health utility score [EuroQol 5-dimension (EQ-5D)] were calculated and compared between CAPD and APD using multivariate linear regression. RESULTS: In total, 266 patients were included, with 145 on CAPD (mean age 60.8 years) and 121 on APD (mean age 57.4 years). After adjustment for all variables collected, APD patients had significant higher scores in PCS and KDQOL symptoms than CAPD patients, suggesting that APD was associated with better physical health and milder dialysis-related symptoms. CONCLUSION: The HRQOL of CAPD and APD patients was largely equivalent in Singapore, but APD patients seemed to experience better physical health and be less bothered by dialysis-related symptoms

Soil Microbial Community: Understanding the Belowground Network for Sustainable Grassland Management

In addition to the use of conventional methodologies in soil microbial research, molecular techniques are now being applied to gain insights into the soil microbial community; Plant diversity can exert impacts on soil microbial diversity (through root activities and plant litter etc.), but may in itself be significantly altered by soil properties; Soil microbial diversity largely determines the stability of soil ecosystems under biotic and abiotic perturbations. Management of soil microbial diversity can only be achieved through better understanding their structures and functions

Soil Microbial Community: Understanding the Belowground Network for Sustainable Grassland Management

Key points 1. In addition to the use of conventional methodologies in soil microbial research, molecular techniques are now being applied to gain insights into the soil microbial community; 2. Plant diversity can exert impacts on soil microbial diversity (through root activities and plant litter etc.), but may in itself be significantly altered by soil properties; 3. Soil microbial diversity largely determines the stability of soil ecosystems under biotic and abiotic perturbations. 4. Management of soil microbial diversity can only be achieved through better understanding their structures and functions