Soil water characteristics of Middle Pleistocene paleosol layers on the loess Plateau

Soil water plays an important role in water quality monitoring, irrigation scheduling, solute migration, and plant growth. The soil water condition for a field site depends on soil type and related water movement parameters. Information about the soil hydraulic properties of Middle Pleistocene paleosol layers within the Yingpan section on the Loess Plateau of China is necessary since it may affect water cycle processes both in vertical and horizontal directions; however, little data is currently available. The saturated hydraulic conductivity (Ks), soil-water characteristic curve (SWCC), field capacity, particle size composition, and other indices of the paleosol layers were determined. Out of a potential eight models to be fitted to the SWCC data, the van Genuchten model was applicable to four layers (S1, S5-2, S5-3 and S6) while the dual porosity equation was applicable to the S2, S3, S4 and S5-1 layers. These models fitted the data well. Results show that paleosol layers differed from each other in their capacity to hold water and this was related to their soil structures and porosities. These differences could be due to the different conditions prevailing during their formation. Although, paleosols occur at various depths, certain deep-rooting plants can access the water they hold. Therefore, the SWCC of the individual layers has significance for ecological management in the region.Key words: Middle Pleistocene, paleosol, soil water characteristic curve, Loess Plateau

Excitonic ferromagnetism in the hexaborides

A ferromagnet with a small spontaneous moment but with a high Curie temperature can be obtained by doping an excitonic insulator made from a spin triplet exciton condensate. Such a condensate can occur in a semimetal with a small overlap or a semiconductor with a small bandgap. We propose that it is responsible for the unexpected ferromagnetism in the doped hexaboride material Ca_{1-x}La_xB_6.Comment: 4 pages, 3 figure

The effects of calcium on the expression of genes involved in ethylene biosynthesis and signal perception during tomato flower abscission

Calcium regulation of the genes involved in ethylene biosynthesis and ethylene receptors in flower abscission zones (AZ) of wild-type tomato (Lycopersicon esculentum Mill.) was investigated in this study. Calcium treatment delayed abscission of pedicel explants. However, verapamil (VP, calcium inhibitor) treatments accelerated abscission. Results showed an increase in AZ ethylene production consistent with abscission in both control and treatment explants. Moreover, in the AZ of flower pedicelstreated with VP, ethylene production, LeACO1 and LeETR1 expression was elevated, but LeETR4 expression decreased. Calcium treatments delayed the onset and maximum ethylene production, maintained low LeACO1 expression and elevated LeETR2, 3, 4, 5 expressions. Results also found that VP and calcium had little effect on LeACS2 expression. Our hypothesis that calcium is integral in preventing ethylene production at the point when 1-aminocyclopropane-1-carboxylic acid (ACC) is converted to ethylene was supported, but the study also revealed the regulation of expression in theethylene receptors. The potential roles of LeACO1, LeETR 3, 4, 5 and calcium in AZs during tomato pedicel explants abscission are discussed

Enhancement of pair creation due to locality in bound-continuum interactions

Electron-positron pair production from vacuum is studied in combined background fields, a binding electric potential well and a laser field. The production process is triggered by the interactions between the bound states in the potential well and the continuum states in the Dirac sea. By tuning the binding potential well, the pair production can be strongly affected by the locality of the bound states. The narrower bound states in position space are more efficient for pair production. This is in contrast to what is commonly expected that the wider extended bound states have larger region to interact with external fields and would thus create more particles. This surprise can be explained as the more localized bound states have a much wider extension in the momentum space, which can enhance the bound-continuum interactions in the creation process. This enhancement manifests itself in both perturbative and non-perturbative production regimes

Momentum-Resolved Electronic Structure of the High-TcT_{c} Superconductor Parent Compound BaBiO3_{3}

We investigate the band structure of BaBiO$_{3}$, an insulating parent compound of doped high-$T_{c}$ superconductors, using \emph{in situ} angle-resolved photoemission spectroscopy on thin films. The data compare favorably overall with density functional theory calculations within the local density approximation, demonstrating that electron correlations are weak. The bands exhibit Brillouin zone folding consistent with known BiO$_{6}$ breathing distortions. Though the distortions are often thought to coincide with Bi$^{3+}$/Bi$^{5+}$ charge ordering, core level spectra show that bismuth is monovalent. We further demonstrate that the bands closest to the Fermi level are primarily oxygen derived, while the bismuth $6s$ states mostly contribute to dispersive bands at deeper binding energy. The results support a model of Bi-O charge transfer in which hole pairs are localized on combinations of the O $2p$ orbitals.Comment: minor changes to text and other figures; includes link to online Supplemental Material; accepted to Phys. Rev. Let

Investigation on Evolving Single-Carrier NOMA into Multi-Carrier NOMA in 5G

© 2013 IEEE. Non-orthogonal multiple access (NOMA) is one promising technology, which provides high system capacity, low latency, and massive connectivity, to address several challenges in the fifth-generation wireless systems. In this paper, we first reveal that the NOMA techniques have evolved from single-carrier NOMA (SC-NOMA) into multi-carrier NOMA (MC-NOMA). Then, we comprehensively investigated on the basic principles, enabling schemes and evaluations of the two most promising MC-NOMA techniques, namely sparse code multiple access (SCMA) and pattern division multiple access (PDMA). Meanwhile, we consider that the research challenges of SCMA and PDMA might be addressed with the stimulation of the advanced and matured progress in SC-NOMA. Finally, yet importantly, we investigate the emerging applications, and point out the future research trends of the MC-NOMA techniques, which could be straightforwardly inspired by the various deployments of SC-NOMA

Downlink MIMO-NOMA for Ultra-Reliable Low-Latency Communications

© 2019 IEEE. With the emergence of the mission-critical Internet of Things applications, ultra-reliable low-latency communications are attracting a lot of attentions. Non-orthogonal multiple access (NOMA) with multiple-input multiple-output (MIMO) is one of the promising candidates to enhance connectivity, reliability, and latency performance of the emerging applications. In this paper, we derive a closed-form upper bound for the delay target violation probability in the downlink MIMO-NOMA, by applying stochastic network calculus to the Mellin transforms of service processes. A key contribution is that we prove that the infinite-length Mellin transforms resulting from the non-negligible interferences of NOMA are Cauchy convergent and can be asymptotically approached by a finite truncated binomial series in the closed form. By exploiting the asymptotically accurate truncated binomial series, another important contribution is that we identify the critical condition for the optimal power allocation of MIMO-NOMA to achieve consistent latency and reliability between the receivers. The condition is employed to minimize the total transmit power, given a latency and reliability requirement of the receivers. It is also used to prove that the minimal total transmit power needs to change linearly with the path losses, to maintain latency and reliability at the receivers. This enables the power allocation for mobile MIMO-NOMA receivers to be effectively tracked. The extensive simulations corroborate the accuracy and effectiveness of the proposed model and the identified critical condition