Spacelike hypersurfaces with negative total energy in de Sitter spacetime

De Sitter spacetime can be separated into two parts along two kinds of hypersurfaces and the half-de Sitter spacetimes are covered by the planar and hyperbolic coordinates respectively. Two positive energy theorems were proved previously for certain $\P$-asymptotically de Sitter and \H-asymptotically de Sitter initial data sets by the second author and collaborators. These initial data sets are asymptotic to time slices of the two kinds of half-de Sitter spacetimes respectively, and their mean curvatures are bounded from above by certain constants. While the mean curvatures violate these conditions, the spacelike hypersurfaces with negative total energy in the two kinds of half-de Sitter spacetimes are constructed in this short paper.Comment: 11 pages, final version, to appear in J. Math. Phy

The Economics of Sustainable Urban Water Management: The Case of Beijing

A rapidly growing urban population leads to the dramatic increase of water consumption in the world. The water resources available to the human being are limited. Meanwhile climate variability and environmental pollution decrease the quantity of water resources available for human use. It is a significant challenge to provide sufficient water to urban residents in a sustainable and effective way. Facing urban water crisis, researchers point out a paradigm shift in urban water management for sustainable water supply and services. This requires multi-disciplinary approaches, including technical improvements and economic evaluations. Advanced technology can contribute to the solution of problems physically, but it may not ensure sustainable operation of wate

Financial and economic feasibility of decentralized wastewater reuse systems in Beijing

Many decentralized wastewater reuse systems have been constructed in Beijing. However their performance is not as good as expected. The total amount of reclaimed water used in Beijing is much less than the designed capacity. In order to understand the reasons causing such poor performance, an integrated financial and economic feasibility analysis for the decentralized wastewater reuse systems in Beijing is carried out in this paper. The monetary values of all the major economic, environmental and social effects are quantified. The financial analysis is made from the viewpoint of the project manager, while the economic analysis is done from the angle of government. The results show that the decentralized wastewater reuse systems in Beijing are economically but not financially feasible. It is found that the low rate actually charged for reclaimed water is an important reason for the system not being financially feasible. The decentralized wastewater reuse systems in Beijing may not continue to operate if the financial problems are not solved

Technical note: Analytical sensitivity analysis and uncertainty estimation of baseflow index calculated by a two-component hydrograph separation method with conductivity as a tracer

The two-component hydrograph separation method with conductivity as a tracer is favored by hydrologists owing to its low cost and easy application. This study analyzes the sensitivity of the baseflow index (BFI, long-term ratio of baseflow to streamflow) calculated using this method to errors or uncertainties in two parameters (BFC, the conductivity of baseflow, and ROC, the conductivity of surface runoff) and two variables (yk, streamflow, and SCk, specific conductance of streamflow, where k is the time step) and then estimates the uncertainty in BFI. The analysis shows that for time series longer than 365 days, random measurement errors in yk or SCk will cancel each other out, and their influence on BFI can be neglected. An uncertainty estimation method of BFI is derived on the basis of the sensitivity analysis. Representative sensitivity indices (the ratio of the relative error in BFI to that of BFC or ROC) and BFI′ uncertainties are determined by applying the resulting equations to 24 watersheds in the US. These dimensionless sensitivity indices can well express the propagation of errors or uncertainties in BFC or ROC into BFI. The results indicate that BFI is more sensitive to BFC, and the conductivity two-component hydrograph separation method may be more suitable for the long time series in a small watershed. When the mutual offset of the measurement errors in conductivity and streamflow is considered, the uncertainty in BFI is reduced by half.</p

On the application of the depth-averaged random walk method to solute transport simulations

Most numerical studies on the solute transport problems relies on mesh-based methods, and complicated schemes have been developed to enhance numerical stability and reduce artificial diffusion. This paper systematically studies the depth-averaged random walk scheme, which is a meshfree method with the merits of being highly robust and free of numerical diffusion. Firstly, the model is used to solve an instantaneous release problem in uniform flows. Extensive parametric studies are carried out to investigate the influences of the number of particles and the size of time steps. The predictions are found to be independent of time steps but are sensitive to the particle numbers. Secondly, the model is applied to the solute transport along a tidal estuary subject to extensive wetting and drying during tidal oscillations. Finally, the model is applied to investigate the wind-induced chaotic mixing in a shallow basin. The effect of diffusion on the chaotic mixing is investigated. This study proposes a generic sampling method to interpret the output of the random walk method and highlights the importance of accurately taking diffusion into account in studying the mixing phenomena. The sampling technique also offers a guideline for estimating the total number of particles needed in the application.Royal Academy of Engineering UK-China Urban Flooding Research Impact Programme (UUFRIP\100051), the 111 Project (B17015), China Scholarship Counci

Molecular cloning and characterization of a chitinase gene up-regulated in longan buds during flowering reversion

A cDNA-amplified fragment length polymorphism (cDNA-AFLP) technique was used for differential screening of genes expressed in longan (Dimocarpus longan Lour.) flower buds undergoing normal development versus flowering reversion. One cDNA fragment up-regulated during flowering reversion was further cloned by rapid amplification of cDNA ends (RACE) technology. This cDNA consists of 961 nucleotides and encodes an open reading frame (ORF) of 227-amino acid residues. The nucleotides and deduced amino acid sequence were both identical against published chitinases from other species and hence this cDNA was designated as DLchi (GenBank accession No. GU177464). It has a signal peptide and glycoside hydrolase’s domain. The estimated molecular weight was 24.77 kD and the isoelectric point was 5.17. This protein might be grouped as a new member of class II chitinase based on the sequences available and hypothesis discussed. DLchi might be involved in the flower bud abscission observed in longan flowering reversion.Key words: Longan, flowering reversion, chitinase gene, cloning, sequence analysis

Insecticide-Mediated Up-Regulation of Cytochrome P450 Genes in the Red Flour Beetle (Tribolium castaneum)

Citation: Liang, X., Xiao, D., He, Y. P., Yao, J. X., Zhu, G. N., & Zhu, K. Y. (2015). Insecticide-Mediated Up-Regulation of Cytochrome P450 Genes in the Red Flour Beetle (Tribolium castaneum). International Journal of Molecular Sciences, 16(1), 2078-2098. doi:10.3390/ijms16012078Some cytochrome P450 (CYP) genes are known for their rapid up-regulation in response to insecticide exposures in insects. To date, however, limited information is available with respect to the relationships among the insecticide type, insecticide concentration, exposure duration and the up-regulated CYP genes. In this study, we examined the transcriptional response of eight selected CYP genes, including CYP4G7, CYP4Q4, CYP4BR3, CYP12H1, CYP6BK11, CYP9D4, CYP9Z5 and CYP345A1, to each of four insecticides in the red flour beetle, Tribolium castaneum. Reverse transcription quantitative PCR (RT-qPCR) revealed that CYP4G7 and CYP345A1 can be significantly up-regulated by cypermethrin (1.97- and 2.06-fold, respectively), permethrin (2.00- and 2.03-fold) and lambda-cyhalothrin (1.73- and 1.81-fold), whereas CYP4BR3 and CYP345A1 can be significantly up-regulated by imidacloprid (1.99- and 1.83-fold) when 20-day larvae were exposed to each of these insecticides at the concentration of LC20 for 24 h. Our studies also showed that similar levels of up-regulation can be achieved for CYP4G7, CYP4BR3 and CYP345A1 by cypermethrin, permethrin, lambda-cyhalothrin or imidacloprid with approximately one fourth of LC20 in 6 h. Our study demonstrated that up-regulation of these CYP genes was rapid and only required low concentrations of insecticides, and the up-regulation not only depended on the CYP genes but also the type of insecticides. Our results along with those from previous studies also indicated that there were no specific patterns for predicting the up-regulation of specific CYP gene families based on the insecticide classification

Investigation of light source effects on digital camera-based spectral estimation

The influence of light sources on digital camera-based spectral estimation is explored. The CIE daylight and non-CIE daylight illuminants with different Correlated Color Temperature (CCT) are first tested comparatively, results indicate that CCT can be used to describe the performance of the CIE daylight illuminants for spectral estimation but not applicable to all types of light sources. To further investigate the mechanism of light effects on spectral estimation, several handmade special shape of Spectral Power Distribution (SPD) are tested, results show that the red component in visible spectrum is crucial for a higher spectral estimation accuracy. Finally, several feature metrics of SPD are proposed to evaluate the performance of the light sources in spectral estimation, results illustrate that the better the feature metrics the better the spectral estimation accuracy

A new class of (2+1)(2+1)-d topological superconductor with Z8\mathbb{Z}_8 topological classification

The classification of topological states of matter depends on spatial dimension and symmetry class. For non-interacting topological insulators and superconductors the topological classification is obtained systematically and nontrivial topological insulators are classified by either integer or $Z_2$. The classification of interacting topological states of matter is much more complicated and only special cases are understood. In this paper we study a new class of topological superconductors in $(2+1)$ dimensions which has time-reversal symmetry and a $\mathbb{Z}_2$ spin conservation symmetry. We demonstrate that the superconductors in this class is classified by $\mathbb{Z}_8$ when electron interaction is considered, while the classification is $\mathbb{Z}$ without interaction.Comment: 5 pages main text and 3 pages appendix. 1 figur

Dissipationless Phonon Hall Viscosity

We study the acoustic phonon response of crystals hosting a gapped time-reversal symmetry breaking electronic state. The phonon effective action can in general acquire a dissipationless "Hall" viscosity, which is determined by the adiabatic Berry curvature of the electron wave function. This Hall viscosity endows the system with a characteristic frequency, \omega_v; for acoustic phonons of frequency \omega, it shifts the phonon spectrum by an amount of order (\omega/\omega_v)^2 and it mixes the longitudinal and transverse acoustic phonons with a relative amplitude ratio of \omega/\omega_v and with a phase shift of +/- \pi/2, to lowest order in \omega/\omega_v. We study several examples, including the integer quantum Hall states, the quantum anomalous Hall state in Hg_{1-y}Mn_{y}Te quantum wells, and a mean-field model for p_x + i p_y superconductors. We discuss situations in which the acoustic phonon response is directly related to the gravitational response, for which striking predictions have been made. When the electron-phonon system is viewed as a whole, this provides an example where measurements of Goldstone modes may serve as a probe of adiabatic curvature of the wave function of the gapped sector of a system.Comment: 14 page