中国稻田温室气体的排放与减排

中国是世界上最大的水稻生产国, 水稻种植面积占全球总种植面积的30%。水稻生产在粮食安全方面起着重要的作用, 稻田却是温室气体甲烷(CH₄)和氧化亚氮(N₂O)的重要排放源。文章综述了稻田CH₄和N₂O的产生过程、影响因素及时空变异规律, 总结了近年来我国稻田CH₄和N₂O排放总量的估算结果, 并提出了针对性的温室气体减排措施。     

Kinetic characterization and modeling of a microalgae consortium isolated from landfill leachate under a high CO2 concentration in a bubble column photobioreactor

BackgroundThe determination of kinetic parameters and the development of mathematical models are of great interest to predict the growth of microalgae, the consumption of substrate and the design of photobioreactors focused on CO₂ capture. However, most of the models in the literature have been developed for CO₂ concentrations below 10%.ResultsA nonaxenic microalgal consortium was isolated from landfill leachate in order to study its kinetic behavior using a dynamic model. The model considered the CO₂ mass transfer from the gas phase to the liquid phase and the effect of light intensity, assimilated nitrogen concentration, ammonium concentration and nitrate concentration. The proposed mathematical model was adjusted with 13 kinetic parameters and validated with a good fit obtained between experimental and simulated data.ConclusionsGood results were obtained, demonstrating the robustness of the proposed model. The assumption in the model of DIC inhibition in the ammonium and nitrate uptakes was correct, so this aspect should be considered when evaluating the kinetics with microalgae with high inlet CO₂ concentrations.How to cite: Saldarriaga L F, Almenglo F, Ramírez M, et al. Kinetic characterization and modeling of a microalgae consortium isolated from landfill leachate under a high CO2 concentration in a bubble column photobioreactor. Electron J Biotechnol 2020;44. https://doi.org/10.1016/j.ejbt.2020.01.006.     

Three Gorges Dam: friend or foe of riverine greenhouse gases?

Dams are often regarded as greenhouse gas (GHG) emitters. However, our study indicated that the world''s largest dam, the Three Gorges Dam (TGD), has caused significant drops in annual average emissions of CO₂, CH₄ and N₂O over 4300 km along the Yangtze River, accompanied by remarkable reductions in the annual export of CO₂ (79%), CH₄ (50%) and N₂O (9%) to the sea. Since the commencement of its operation in 2003, the TGD has altered the carbonate equilibrium in the reservoir area, enhanced methanogenesis in the upstream, and restrained methanogenesis and denitrification via modifying anoxic habitats through long-distance scouring in the downstream. These findings suggest that ‘large-dam effects’ are far beyond our previous understanding spatiotemporally, which highlights the fundamental importance of whole-system budgeting of GHGs under the profound impacts of huge dams.     

Light-driven directional ion transport for enhanced osmotic energy harvesting

Light-driven ion (proton) transport is a crucial process both for photosynthesis of green plants and solar energy harvesting of some archaea. Here, we describe use of a TiO₂/C₃N₄ semiconductor heterojunction nanotube membrane to realize similar light-driven directional ion transport performance to that of biological systems. This heterojunction system can be fabricated by two simple deposition steps. Under unilateral illumination, the TiO₂/C₃N₄ heterojunction nanotube membrane can generate a photocurrent of about 9 μA/cm², corresponding to a pumping stream of ∼5500 ions per second per nanotube. By changing the position of TiO₂ and C₃N₄, a reverse equivalent ionic current can also be realized. Directional transport of photogenerated electrons and holes results in a transmembrane potential, which is the basis of the light-driven ion transport phenomenon. As a proof of concept, we also show that this system can be used for enhanced osmotic energy generation. The artificial light-driven ion transport system proposed here offers a further step forward on the roadmap for development of ionic photoelectric conversion and integration into other applications, for example water desalination.     

Detection and correction of incomplete duplicate 24-hour urine collections – theory and practical evidence

IntroductionThe intraindividual variability in urinary creatinine excretion is notoriously large. The aims of this study were to investigate the variability of duplicate consecutive 24-hour urinary creatinine excretions in patients and to develop a model for the detection and correction of discrepant creatinine excretions.Materials and methodsA group of 270 patients (82 men and 188 women) were included in the study. We collected the following data: urinary 24-hour volumes (volumetric/gravimetric) and urinary creatinine concentrations (Jaffé/enzymatic) on both collection days. We performed specific calculations to detect discrepant creatinine excretions.ResultsIn 60 patients (22%) discrepant collections were found. Among the remaining 78%, 22% of the patients collected very accurately (almost identical urinary creatinine excretions). In this subgroup the volume ratios and the creatinine concentration ratios behave inversely as in a dilution curve. A theoretical model and six collection scenarios were developed to detect, interpret and correct discrepant collections. Practical examples are given to illustrate the use of the model in successful correction of creatinine and other analytes for under- or overcollection.ConclusionsWe conclude that missed or overcollected urine volumes are the largest source of variation in creatinine excretion. Discrepancies in consecutive duplicate 24-hour creatinine excretions can be detected and corrected with specific calculations by means of the presented model. The effectiveness of these corrections is demonstrated with examples from daily practice. These calculations can be easily automated.     

1000 Wh L−1 lithium-ion batteries enabled by crosslink-shrunk tough carbon encapsulated silicon microparticle anodes

Microparticulate silicon (Si), normally shelled with carbons, features higher tap density and less interfacial side reactions compared to its nanosized counterpart, showing great potential to be applied as high-energy lithium-ion battery anodes. However, localized high stress generated during fabrication and particularly, under operating, could induce cracking of carbon shells and release pulverized nanoparticles, significantly deteriorating its electrochemical performance. Here we design a strong yet ductile carbon cage from an easily processing capillary shrinkage of graphene hydrogel followed by precise tailoring of inner voids. Such a structure, analog to the stable structure of plant cells, presents ‘imperfection-tolerance’ to volume variation of irregular Si microparticles, maintaining the electrode integrity over 1000 cycles with Coulombic efficiency over 99.5%. This design enables the use of a dense and thick (3 mAh cm^–2) microparticulate Si anode with an ultra-high volumetric energy density of 1048 Wh L^–1 achieved at pouch full-cell level coupled with a LiNi_0.8Co_0.1Mn_0.1O₂ cathode.     

Sealing SU-8 microfluidic channels using PDMS

A simple method of irreversibly sealing SU-8 microfluidic channels using PDMS is reported in this paper. The method is based on inducing a chemical reaction between PDMS and SU-8 by first generating amino groups on PDMS surface using N₂ plasma treatment, then allowing the amino groups to react with the residual epoxy groups on SU-8 surface at an elevated temperature. The N₂ plasma treatment of PDMS can be conducted using an ordinary plasma chamber and high purity N₂, while the residual epoxy groups on SU-8 surface can be preserved by post-exposure baking SU-8 at a temperature no higher than 95 °C. The resultant chemical bonding between PDMS and SU-8 using the method create an interface that can withstand a stress that is greater than the bulk strength of PDMS. The bond is permanent and is long-term resistant to water. The method was applied in fabricating SU-8 microfluidi-photonic integrated devices, and the obtained devices were tested to show desirable performance.     

Superconductivity in chromium nitrides Pr3Cr10-xN11 with strong electron correlations

Exploration of superconductivity in Cr-based compounds has attracted considerable interest because only a few Cr-based superconductors (CrAs, A₂Cr₃As₃ and ACr₃As₃ (A = K, Rb, Cs, Na)) have been discovered so far and they show an unconventional pairing mechanism. We report the discovery of bulk superconductivity at 5.25 K in chromium nitride in Pr₃Cr_10-xN₁₁ with a cubic lattice structure. A relatively large upper critical field of H_c2(0) ∼ 12.6 T is determined, which is larger than the estimated Pauli-paramagnetic pair-breaking magnetic field. The material has a large electronic specific-heat coefficient of 170 mJ K⁻² mol⁻¹—about 10 times larger than that estimated by the electronic structure calculation, which suggests that correlations between 3d electrons are very strong in Pr₃Cr_10-xN₁₁, and thus quantum fluctuations might be involved. Electronic structure calculations show that the density of states at the Fermi energy are contributed predominantly by Cr 3d electrons, implying that the superconductivity results mainly from the condensation of Cr 3d electrons. Pr₃Cr_10-xN₁₁ represents a rare example of possible unconventional superconductivity emerging in a 3D system with strong electron correlations. Nevertheless, clarification of the specific pairing symmetry needs more investigation.     

Altering the rate-determining step over cobalt single clusters leading to highly efficient ammonia synthesis

Activation of high-energy triple-bonds of N₂ is the most significant bottleneck of ammonia synthesis under ambient conditions. Here, by importing cobalt single clusters as strong electron-donating promoter into the catalyst, the rate-determining step of ammonia synthesis is altered to the subsequent proton addition so that the barrier of N₂ dissociation can be successfully overcome. As revealed by density functional theory calculations, the N₂ dissociation becomes exothermic over the cobalt single cluster upon the strong electron backdonation from metal to the N₂ antibonding orbitals. The energy barrier of the positively shifted rate-determining step is also greatly reduced. At the same time, advanced sampling molecular dynamics simulations indicate a barrier-less process of the N₂ approaching the active sites that greatly facilitates the mass transfer. With suitable thermodynamic and dynamic property, a high ammonia yield rate of 76.2 μg h^–1 mg and superior Faradaic efficiency of 52.9% were simultaneously achieved.     

Direct transformation of dinitrogen: synthesis of N-containing organic compounds via N−C bond formation

N-containing organic compounds are of vital importance to lives. Practical synthesis of valuable N-containing organic compounds directly from dinitrogen (N₂), not through ammonia (NH₃), is a holy-grail in chemistry and chemical industry. An essential step for this transformation is the functionalization of the activated N₂ units/ligands to generate N−C bonds. Pioneering works of transition metal-mediated direct conversion of N₂ into organic compounds via N−C bond formation at metal-dinitrogen [N₂-M] complexes have generated diversified coordination modes and laid the foundation of understanding for the N−C bond formation mechanism. This review summarizes those major achievements and is organized by the coordination modes of the [N₂-M] complexes (end-on, side-on, end-on-side-on, etc.) that are involved in the N−C bond formation steps, and each part is arranged in terms of reaction types (N-alkylation, N-acylation, cycloaddition, insertion, etc.) between [N₂-M] complexes and carbon-based substrates. Additionally, earlier works on one-pot synthesis of organic compounds from N₂ via ill-defined intermediates are also briefed. Although almost all of the syntheses of N-containing organic compounds via direct transformation of N₂ so far in the literature are realized in homogeneous stoichiometric thermochemical reaction systems and are discussed here in detail, the sporadically reported syntheses involving photochemical, electrochemical, heterogeneous thermo-catalytic reactions, if any, are also mentioned. This review aims to provide readers with an in-depth understanding of the state-of-the-art and perspectives of future research particularly in direct catalytic and efficient conversion of N₂ into N-containing organic compounds under mild conditions, and to stimulate more research efforts to tackle this long-standing and grand scientific challenge.     

中国农田非CO2温室气体减排的研究现状与建议

温室气体减排对控制全球气候变暖具有重要意义。2014年我国农田非CO₂温室气体(主要指CH₄和N₂O)排放占全国温室气体排放总量的4.3%,预计2030年我国实现碳达峰后,化石能源逐步被清洁能源替代,农田CH₄和N₂O排放占全国温室气体排放的比重也将随之增大,其减排的紧迫性和重要性将日渐凸显。然而,现有农田碳减排技术由于缺乏立法教育宣传和成果激励机制等,并未得到充分转化应用与推广示范,使得减排成果难以落地坐实,不利于我国农业碳减排目标的顺利实现。文章总结了我国农田CH₄和N₂O减排工作的研究进展,指出了当前我国农田CH₄和N₂O减排所面临的问题,并在今后长效监测平台运维、新方法技术突破、大众减排意识提升及成果推广示范加强4个方面提出了技术和政策上的建议。     

Scalable fabrication of printed Zn//MnO2 planar micro-batteries with high volumetric energy density and exceptional safety

The rapid development of printed and microscale electronics imminently requires compatible micro-batteries (MBs) with high performance, applicable scalability, and exceptional safety, but faces great challenges from the ever-reported stacked geometry. Herein the first printed planar prototype of aqueous-based, high-safety Zn//MnO₂ MBs, with outstanding performance, aesthetic diversity, flexibility and modularization, is demonstrated, based on interdigital patterns of Zn ink as anode and MnO₂ ink as cathode, with high-conducting graphene ink as a metal-free current collector, fabricated by an industrially scalable screen-printing technique. The planar separator-free Zn//MnO₂ MBs, tested in neutral aqueous electrolyte, deliver a high volumetric capacity of 19.3 mAh/cm³ (corresponding to 393 mAh/g) at 7.5 mA/cm³, and notable volumetric energy density of 17.3 mWh/cm³, outperforming lithium thin-film batteries (≤10 mWh/cm³). Furthermore, our Zn//MnO₂ MBs present long-term cyclability having a high capacity retention of 83.9% after 1300 cycles at 5 C, which is superior to stacked Zn//MnO₂ batteries previously reported. Also, Zn//MnO₂ planar MBs exhibit exceptional flexibility without observable capacity decay under serious deformation, and remarkably serial and parallel integration of constructing bipolar cells with high voltage and capacity output. Therefore, low-cost, environmentally benign Zn//MnO₂ MBs with in-plane geometry possess huge potential as high-energy, safe, scalable and flexible microscale power sources for direction integration with printed electronics.     

On metrics matched to the discrete memoryless channel

A sequence of metrics {D_N} is said to be additive and matched to a discrete memoryless channel (DMC) if D_N is the sum on its coordinates of N single letter metrics and if the maximum likelihood decoder for sequences of length N is a minimum D_N-distance decoder. Necessary and sufficient conditions on the transition probabilities of a DMC for the existence of a sequence of additive metrics matched to it are given. In the case of the binary channel these are shown to be equivalent to the channel being symmetric. Explicit transition probabilities are given for a large class of ternary DMCs with an associated sequence of additive matched metrics. The problem solved here may be considered a generalization of the problem of finding the DMCs matched to the Lee metric solved by Chiang and Wolf in 1971 (2).     

Antidyslipidaemic activity of <Emphasis Type="Italic">Glycyrrhiza glabra</Emphasis> in high fructose diet induced dsyslipidaemic Syrian golden hamsters

The root of Glycyrrhiza glabra is a traditional medicine used mainly for the treatment of peptic ulcer, hepatitis C, pulmonary and skin diseases, although clinical and experimental studies suggest that it has several other useful pharmacological properties such as antiinflammatory, antiviral, antimicrobial, antioxidative, anticancer activities, immunomodulatory, hepatoprotective and cardioprotective effects. Glycyrrhizinic acid, a major component of licorice, has antiulcer effect by raising the local concentration of prostaglandins that promote mucous secretion and cell proliferation in the stomach. Glycyrrhizin shows hepatoprotective effect by preventing changes in cell membrane permeability, inhibiting phospholipase A₂ (PLA₂) and increasing survival rate of hepatocytes. Glabridin has effect in melanogenesis and inflammation by inhibiting the tyrosinase activity of melanocytes. α-glycyhrritinic acid exhibits anti-inflammatory activity by inhibiting glucocorticoid metabolism. In present study ethanolic (95%) extract of root of Glycyrrhiza glabra and its fractions were investigated for its antidyslipidaemic activity on HFD induced dyslipidaemic hamsters. Ethanolic extract and its ethyl acetate soluble, water soluble and hexane soluble fractions decreased serum level of total cholesterol by 25.9, 38.0, 39.0 and 26.3%, respectively. On the other hand ethanolic extract, ethyl acetate soluble, water soluble and hexane soluble fraction increased the serum HDL-cholesterol level by 14.8, 34.3, 27.3 and 17.2%, respectively. Ethanolic extract, ethyl acetate fraction, aqueous fraction and hexane fraction decreased triglyceride level by 31.3, 37.2, 41.2 and 28.9%, respectively. The reduction in LDL-cholesterol level by ethanolic extract, ethyl acetate soluble fraction and water soluble fraction were 43.9, 31.0, 33.4 and 24.6%, respectively.     

Direct and green repairing of degraded LiCoO2 for reuse in lithium-ion batteries

Traditional recycling processes of LiCoO₂ rely on destructive decomposition, requiring high-temperature roasting or acid leaching to extract valuable Li and Co, which have significant environmental and economic concerns. Herein, a direct repairing method for degraded LiCoO₂ using a LiCl–CH₄N₂O deep eutectic solvent (DES) was established. The DES is not used to dissolve LiCoO₂ but directly serves as a carrier for the selective replenishment of lithium and cobalt. Replenishment of lithium restores LiCoO₂ at different states of charge to a capacity of 130 mAh/g (at 0.1 C rate), while replenishing the cobalt increases the capacity retention rate of 90% after 100 cycles, which is comparable to pristine LiCoO₂. The DES is collected and reused multiple times with a high repair efficiency. This process reduces energy consumption by 37.1% and greenhouse gas emissions by 34.8% compared with the current production process of LiCoO₂, demonstrating excellent environmental and economic viability.     

基于MODIS数据的泰国林地资源提取

遥感技术的发展为我们对世界资源的研究提供了新的手段,克服了世界资源研究过程中数据缺乏的困难。泰国曾经是林地资源丰富的国家,尤其是热带林地资源,但是近几十年来林地面积在不断减少,带来了一系列生态问题。选用MOD09Q1的1、2波段,MOD09A1的第6波段以及MOD11A2数据产品提取了泰国林地分布情况。由于泰国地处热带地区云雾噪音为林地的提取造成了很大的不确定性,为了有效去除云雾噪音影响,结合NDVI、NDSI、LST多参数在林地提取中的优势对泰国林地进行提取。采用泰国2003年统计年鉴提供的分省林地面积以及2003年p131r47和p131r48共2景ETM影像进行了精度验证。结果表明,利用多参数综合分类方法对林地提取精度较高,通过与2003年统计年鉴数据进行回归分析发现二者存在明显的线性关系,决定系数达到0.9264。     

澜沧江流域潜在蒸散发敏感性分析

蒸散发对气候变量的敏感性研究是近年来水文学的热点之一,对探讨水循环对气候变化的响应具有重要意义。本文利用1960年-2005年澜沧江流域及其周边35个气象站的逐日常规气象观测数据,基于Penman-Monteith公式,计算了1月、7月及年3个不同时间尺度下潜在蒸散发对平均气温、相对湿度、风速及日照时数的敏感系数,分析了澜沧江流域潜在蒸散发对各气候变量的敏感性及其时空变化规律。结果表明各站潜在蒸散发对各变量的敏感系数空间分异明显,流域整体上对日照时数最为敏感。几十年来对日照时数的敏感性在1月主要为增加趋势,7月则为减小趋势。     

The effects of different syringe volume, needle size and sample volume on blood gas analysis in syringes washed with heparin

Introductıon:

We evaluated the effect of different syringe volume, needle size and sample volume on blood gas analysis in syringes washed with heparin.

Materials and methods:

In this multi-step experimental study, percent dilution ratios (PDRs) and final heparin concentrations (FHCs) were calculated by gravimetric method for determining the effect of syringe volume (1, 2, 5 and 10 mL), needle size (20, 21, 22, 25 and 26 G) and sample volume (0.5, 1, 2, 5 and 10 mL). The effect of different PDRs and FHCs on blood gas and electrolyte parameters were determined. The erroneous results from nonstandardized sampling were evaluated according to RiliBAK’s TEa.

Results:

The increase of PDRs and FHCs was associated with the decrease of syringe volume, the increase of needle size and the decrease of sample volume: from 2.0% and 100 IU/mL in 10 mL-syringe to 7.0% and 351 IU/mL in 1 mL-syringe; from 4.9% and 245 IU/mL in 26G to 7.6% and 380 IU/mL in 20 G with combined 1 mL syringe; from 2.0% and 100 IU/mL in full-filled sample to 34% and 1675 IU/mL in 0.5 mL suctioned sample into 10 mL-syringe. There was no statistical difference in pH; but the percent decreasing in pCO₂, K⁺, iCa²⁺, iMg²⁺; the percent increasing in pO₂ and Na⁺ were statistical significance compared to samples full-filled in syringes. The all changes in pH and pO₂ were acceptable; but the changes in pCO₂, Na⁺, K⁺ and iCa²⁺ were unacceptable according to TEa limits except fullfilled-syringes.

Conclusions:

The changes in PDRs and FHCs due nonstandardized sampling in syringe washed with liquid heparin give rise to erroneous test results for pCO₂ and electrolytes.     

Vector incremental L2-gain and incremental stability for switched nonlinear systems

This paper studies vector incremental L₂-gain and incremental stability for switched nonlinear systems using individual incremental gains and multiple storage functions. Firstly, a vector incremental L₂-gain concept for switched nonlinear systems is proposed. Each subsystem is not required to have incremental L₂-gain, but it has its own incremental L₂-gain and the related storage function, when it is active. The transformation of “energy” from the active subsystem to each inactive subsystem is characterized by cross-supply rates. Then, we show that a switched nonlinear system who has vector incremental L₂-gain can be incrementally stabilized under some constraints on the energy change of inactive subsystems. Secondly, a state-dependent switching law is designed to achieve vector incremental L₂-gain, even if each subsystem does not have incremental L₂-gain in the classic sense. Thirdly, each switched system is not required to have vector incremental L₂-gain, but the feedback interconnection of switched nonlinear systems is incrementally stabilized by the design of a composite switching law. The switching law allows the two switched systems switch asynchronously. Two examples are provided to verify the effectiveness of the proposed method.     

(NH4)3B11PO19F3: a deep-UV nonlinear optical crystal with unique [B5PO10F]∞ layers

Deep-ultraviolet (DUV) nonlinear optical (NLO) crystals that can extend the output range of coherent light below 200 nm are pivotal materials for solid-state lasers. To date, KBe₂BO₃F₂ (KBBF) is the only usable crystal that can generate DUV coherent light by direct second harmonic generation (SHG), but the layered growth habit and toxic ingredients limit its application. Herein, we report a new fluoroborophosphate, (NH₄)₃B₁₁PO₁₉F₃ (ABPF), containing four different functional units: [BO₃], [BO₄], [BO₃F] and [PO₄]. ABPF exhibits a KBBF-like structure while eliminating the limitations of KBBF crystal. The unique [B₅PO₁₀F]_∞ layers enhance ABPF’s performance; for example, it has a large SHG response (1.2 × KDP) and a sufficient birefringence (0.088 at 1064 nm) that enables the shortest phase-matching wavelength to reach the DUV region. Meanwhile, the introduction of strong B-O-P covalent bonds decreases the layered growth habit. These findings will enrich the structural chemistry of fluoroborophosphate and contribute to the discovery of more excellent DUV NLO crystals.