A Family of Lanthanide Noncentrosymmetric Superconductors La4_4TXTX (TT = Ru, Rh, Ir; XX = Al, In)

We report the discovery of superconductivity in a series of noncentrosymmetric compounds La$_4$$TX$ ($T$ = Ru, Rh, Ir; $X$ = Al, In), which have a cubic crystal structure with space group $F\bar{4}3m$. La$_4$RuAl, La$_4$RhAl, La$_4$IrAl, La$_4$RuIn and La$_4$IrIn exhibit bulk superconducting transitions with critical temperatures $T_c$ of 1.77 K, 3.05 K, 1.54 K, 0.58 K and 0.93 K, respectively. The specific heat of the La$_4$$T$Al compounds are consistent with an $s$-wave model with a fully open superconducting gap. In all cases, the upper critical fields are well described by the Werthamer-Helfand-Hohenberg model, and the values are well below the Pauli limit, indicating that orbital limiting is the dominant pair-breaking mechanism. Density functional theory (DFT) calculations reveal that the degree of band splitting by the antisymmetric spin-orbit coupling (ASOC) shows considerable variation between the different compounds. This indicates that the strength of the ASOC is highly tunable across this series of superconductors, suggesting that these are good candidates for examining the relationship between the ASOC and superconducting properties in noncentrosymmetric superconductors.Comment: 10 pages, 7 figure

A digital audio equalizer with Optimal Error Feedback Structure

A digital audio equalizer (EQ) with optimal Error Feedback (EF) structure is presented and implemented based on FPGA in this paper. The signal processed by this EQ is 24bits digital audio signal of PCM format, and the coefficients are of 27 bits length. As the feedback coefficients are adjusted with the poles of the Optimal Error Feedback Structures, the distinguishing advantage of this proposed equalizer is that it can completely eliminate the truncation noise caused by the poles when comparing with current technology. ? 2010 IEEE.EI

Moderate grazing has little effect on global warming potential in the temperate steppes of northern China

Grazing has been reported to significantly affect the flux of three greenhouse gases (GHGs: CO2, CH4 and N2O) in grasslands, but its effect on total global warming potential (GWP) is still unclear. To assess the effect of grazing on GWP, we simultaneously measured the flux of these three GHGs using static chambers in meadow, typical, and desert steppes under no grazing (NG) and summer grazing (SG) conditions during the 2012-14 growing seasons. We aimed to examine the impact of grazing on total GWP across different steppes and to assess the relative contribution of different environmental factors to changes in GWP. Our results showed that total GWP values were almost entirely negative in all steppe environments and displayed high spatio-temporal variability. Net ecosystem exchange was the most important predictor of total GWP in all three steppes, and the positive GWP induced by N2O emission was approximately equal to the negative GWP induced by CH4 uptake. Steppe type and sampling year-but not grazing treatment-were found to affect GWP. Air temperature and precipitation were the major factors driving total GWP change under the no grazing treatment. In contrast, soil temperature, soil moisture, and precipitation explained a significant percentage of variation in total GWP under the summer grazing treatment. Our study suggests that moderate grazing does not change the role of temperate steppe's function in mitigating climate change; however, multi-year GWP data are necessary for extrapolation to a regional scale

Effects of grazing on CO2, CH4, and N2O fluxes in three temperate steppe ecosystems

Terrestrial ecosystems play a critical role in regulating the emission and uptake of the most important greenhouse gases (GHGs) such as CO2, CH4, and N2O. However, the effects of grazing on these GHG fluxes in different steppe types remain unclear. Here, we compared the effects of grazing on seasonal CO2, CH4, and N2O fluxes in the meadow (MS), typical (TS), and desert (DS) temperate steppe ecosystems in northern China. CO2 emission rates increased from 311.4 +/- 73.2 to 349.6 +/- 55.4 mg.m(-2).h(-1) in MS, but decreased in TS (from 341.3 +/- 93.0 to 239.5 +/- 81.9 mg.m(-2).h(-1)) and DS ( from 212.1 +/- 53.7 to 163.0 +/- 83.4 mg.m(-2).h(-1)) in response to summer grazing (SG). N2O emission rates increased in MS from 4.7 +/- 2.2 to 8.1 +/- 3.4 mu g.m(-2).h(-1), but not significantly changed in TS (9.2 +/- 4.2 vs. 8.4 +/- 2.4 mu g.m(-2).h(-1)) and DS (6.3 +/- 1.5 vs. 5.7 +/- 1.6 mu g.m(-2).h(-1)) by SG. CH4 uptake rates increased in MS from 33.0 +/- 11.7 to 47.1 +/- 10.4 mu g.m(-2).h(-1) and decreased from 64.4 +/- 7.6 to 56.2 +/- 5.9 mu g.m(-2).h(-1) in TS in response to SG. In MS and DS, N2O emissions were positively related to seasonal CO2 emissions and negatively related to CH4 uptakes. No significant relationships were found between GHG fluxes in TS. Summer grazing did not affect the relationship between CO2 and N2O emissions in MS, but reduced the relationship by enhancing the effect of aboveground biomass (AGB) on N2O emission in DS. The significant negative relationship between CH4 uptake and N2O emission in MS and DS could be attributed to the significant relationship between soil temperature (ST) and AGB in MS and to the significant effects of soil moisture on both CH4 uptake and N2O emission in DS. The decrease in the magnitude of the correlation coefficients between CH4 uptake and N2O emission by SG was due to the negative relationship between ST and AGB simultaneously in MS and DS. Our results suggest that effects of SG on GHG fluxes varied in different steppes and the relationship among GHGs was steppe-dependent and SG also changed the relationship by affecting GHG fluxes induced by varied soil and environmental factors

Ag₂CO₃ Decorating BiOCOOH Microspheres with Enhanced Full-Spectrum Photocatalytic Activity for the Degradation of Toxic Pollutants

The development of excellent full-spectrum photocatalysts is of vital significance to its practical application in environmental remediation. Herein, flower-like Ag2CO3/BiOCOOH type I heterostructures were prepared via a facile method and exhibited powerful photocatalytic activity by removing various toxic pollutants (rhodamine B, methyl blue, and tetracycline hydrochloride) under simulated sunlight irradiation. The boosted photocatalytic performance is attributed to the expanded range of the absorption spectrum and alleviated separation rate of the photo-induced electrons and holes. The photoluminescence spectra and trapping experiment were applied to clarify the photocatalytic reaction mechanism of Ag2CO3/BiOCOOH. The holes and •O2− were detected as the dominant reactive species involved in pollutant degradation. This work provides a novel full-spectrum-driven photocatalyst of Ag2CO3/BiOCOOH, which could effectively degrade toxic pollutants under simulated sunlight