贵州的短尾鼩(Anourosorex)化石

贵州发现的属于食虫类 Anourosorex 属的182件标本按齿式可分为两种类型,齿式为的是 A kui; 齿式为的是两新种, A. edwardsi sp. nov. 和 A. qianensis sp. nov.. 含有 A. kui 的岩灰洞、天门洞及穿洞动物群的地质时代可与四川盐井沟及歌乐山中更新世中晚期动物群相对比. A. kui 与较原始的 A. edwardsi 共生的岩灰洞和穿洞动物群的时代可能较之天门洞稍早.较进步的绝灭种 A. qianensis 单独存在于挖竹湾洞、天桥裂隙、白脚岩洞并和云南呈贡三家村晚更新世地点的材料可以对比. 根据齿式及形态特征 A. kui 应是现生种 A. squamipes 的直接祖先.     

N-acetylglucosaminyl transferases from the pupal instar of the stable fly,Stomoxys calcitrans

N-acetylglucosaminyl transferases from pupae of Stomoxys calcitrans (L.) were studied in 10,000g pellet suspensions. Characterization of these enzymes was based on formation of glycolipids (ie, Dol·PP-GlcNAc and Dol·PP-(GlcNAc)₂), oligosaccharide lipids, and giycoproteins. Studies on transferase activity during the pupal instar showed that there were two peaks of activity; the first peak was on day 0 (prepupae) and the second at 3 days after pupation. Subcellular fractionation indicated that 10,000g and 100,000g pellets contained most of the transferase activities. The transferases required divalent cations (either Mn²⁺ or Mg²⁺). The pH optimum, which varied for each of the products formed, was 7.5 for glycolipids, 7.0 for oligosaccharide lipids, and 6.5 for glycoprotein. Inclusion of dolichol monophosphate doubled the amount of Dol·PP-GlcNAc and Dol·PP·(GlcNAc)₂ formed, but had little effect on oligosaccharide lipid and glycoprotein formation. Tunicamycin was a potent inhibitor of glycolipid formation with an I₅₀ of 1.8–4.8 nM. It was confirmed that tunicamycin acts by preventing the transfer of GlcNAc-1-P from UDP-GlcNAc to Dol·P. UMP reverses glycolipid formation, yielding UDP-GlcNAc. Some characterization of the products was performed. Glycolipids were shown to be Dol·PP-GlcNAc and Dol·PP-(GlcNAc)₂. Glycoprotein was rapidly solubilized by protease and detergent treatments, whereas oligosaccharide lipids appeared to be acid-labile, pyrophosphate-containing lipids. The apparent kinetic constants for the formation of glycolipids were as follows: UDP-GlcNAc K_m = 1.55 ± 0.47 μM, V_max = 0.66 ± 0.21 pmol·min^?1·mg^?1; Dol·P K_m = 2.08 ± 0.85 μM, V_max = 0.13 ± 0.06 pmol·min^?1·mg^?1 protein.     

Risk assessment and source identification of coastal groundwater nitrate in northern China using dual nitrate isotopes combined with Bayesian mixing model

Due to the intensive and complicated human activities, the identification of nitrate pollution source of coastal aquifer is usually a challenge. This study firstly adopted stable isotope technique and stable isotope analysis in R (SIAR) model to identify the nitrate sources and contribution proportions of different sources in typical coastal groundwater of northern China. The results showed that about 91.5% of the groundwater samples illustrated significantly high nitrate concentrations exceeding the maximum WHO drinking water standard (50 mg/l), reflecting the high risk of groundwater nitrate pollution in the coastal area. A total of 57 sampling sites were classified into three groups according to hierarchical cluster analysis (HCA). The δ¹⁵N-NO₃^? and δ¹⁸O-NO₃^? values of groundwater samples from Group C (including nine samples) were much higher than those from Group A (including 40 samples) and Group B (including 8 samples). SIAR results showed that NH₄⁺ fertilizer was the dominant nitrate source for groundwater samples of Groups A and B while manure and sewage (M&;S) served as dominant source for Group C. This study provided essential information on the high risk and pollution sources of coastal groundwater nitrate of northern China.     

High Energy Density Sodium‐Ion Battery with Industrially Feasible and Air‐Stable O3‐Type Layered Oxide Cathode

Extensive effort is being made into cathode materials for sodium‐ion battery to address several fatal issues, which restrict their future application in practical sodium‐ion full cell system, such as their unsatisfactory initial Coulombic efficiency, inherent deficiency of cyclable sodium content, and poor industrial feasibility. A novel air‐stable O3‐type Na[Li_0.05Mn_0.50Ni_0.30Cu_0.10Mg_0.05]O₂ is synthesized by a coprecipitation method suitable for mass production followed by high‐temperature annealing. The microscale secondary particle, consisting of numerous primary nanocrystals, can efficiently facilitate sodium‐ion transport due to the short diffusion distance, and this cathode material also has inherent advantages for practical application because of its superior physical properties. It exhibits a reversible capacity of 172 mA h g^?1 at 0.1 C and remarkable capacity retention of 70.4% after 1000 cycles at 20 C. More importantly, it offers good compatibility with pristine hard carbon as anode in the sodium‐ion full cell system, delivering a high energy density of up to 215 W h kg^?1 at 0.1 C and good rate performance. Owing to the high industrial feasibility of the synthesis process, good compatibility with pristine hard carbon anode, and excellent electrochemical performance, it can be considered as a promising active material to promote progress toward sodium‐ion battery commercialization.     

Ultra‐Lightweight 3D Carbon Current Collectors: Constructing All‐Carbon Electrodes for Stable and High Energy Density Dual‐Ion Batteries

Dual‐ion batteries (DIBs) attract great interest because they allow two types of ions for reversibly intercalating into electrodes, resulting in various advantages. However, there are three critical problems using graphite‐based cathodes, namely, low active material proportion in the electrodes, current collector corrosion, and massive cathode variation. For addressing these problems, an ultra‐lightweight 3D carbon current collector (CCC) is developed to fabricate all‐carbon electrodes as both cathodes and anodes. Compared with the conventional DIBs using Al and Cu foils as current collectors, the DIBs with 3D CCC of electrically conductive pathways and sufficient ionic diffusion channels deliver enhanced specific capacity stabilized around 140 and 120 mAh g^?1 at 0.5 and 1C, respectively. The electrochemically inert 3D CCC could essentially promote the energy density when calculating the entire electrode mass, along with long‐life cycle stability of 1000 cycles at 5C and no electrochemical corrosion on either anodes or cathodes. With an in situ optical microscope, the cathode expansion is found to massively reduce because the porous 3D CCC could effectively alleviate the huge volume. The results suggest a novel strategy for achieving low‐cost and high energy density DIBs with both mechanically and electrochemically stable features.     

Seeking alternative stable states in a deep lake

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Robustness of early warning signals for catastrophic and non‐catastrophic transitions

Early warning signals (EWS) are statistical indicators that a rapid regime shift may be forthcoming. Their development has given ecologists hope of predicting rapid regime shifts before they occur. Accurate predictions, however, rely on the signals being appropriate to the system in question. Most of the EWS commonly applied in ecology have been studied in the context of one specific type of regime shift (the type brought on by a saddle‐node bifurcation, at which one stable equilibrium point collides with an unstable equilibrium and disappears) under one particular perturbation scheme (temporally uncorrelated noise that perturbs the net population growth rate in a density independent way). Whether and when these EWS can be applied to other ecological situations remains relatively unknown, and certainly underappreciated. We study a range of models with different types of dynamical transitions (including rapid regime shifts) and several perturbation schemes (density‐dependent uncorrelated or temporally‐correlated noise) and test the ability of EWS to warn of an approaching transition. We also test the sensitivity of our results to the amount of available pre‐transition data and various decisions that must be made in the analysis (i.e. the rolling window size and smoothing bandwidth used to compute the EWS). We find that EWS generally work well to signal an impending saddle‐node bifurcation, regardless of the autocorrelation or intensity of the noise. However, EWS do not reliably appear as expected for other types of transition. EWS were often very sensitive to the length of the pre‐transition time series analyzed, and usually less sensitive to other decisions. We conclude that the EWS perform well for saddle‐node bifurcation in a range of noise environments, but different methods should be used to predict other types of regime shifts. As a consequence, knowledge of the mechanism behind a possible regime shift is needed before EWS can be used to predict it.     

Les ostracodes plio-pléistocènes de la côte orientale de la Péninsule du Cap Bon (Tunisie)

This article concerns the study of the ostracods of the Upper Pliocene-Lower Pleistocene sedimentary deposits cropping out along the south-eastern coast of the Cape Bon Peninsula (Tunisia, Hammamet region, Sidi Khelas section). Fourteen samples were taken along a thirty-two-meters thick sedimentary silico-clastic series. Seventy species of ostracods belonging to twenty-four genera were found. The autochthonous association, which originally lived in an environment located in the infralittoral and upper circalittoral stages of the benthic marine domain, is cyclically affected by inputs from the more superficial environments due to the presence of relatively well-developed lagoon and/or estuary environments in the surrounding coastal areas. Within the ostracod association, the presence of Bythocythere turgida – a true “northern guest” – is particularly significant. This species indicates that these sediments were deposited during the cold phases of the Early Pleistocene. Among the ostracods found, those belonging to the families Trachyleberididae, Hemicytheridae and Bythocytheridae, which are dominant and include particularly significant species from the environmental and paleoclimatic point of view, are systematically recorded and commented on. Some species that are probably new have been described and photographed, but are currently left in open nomenclature because of how few specimens have been found.