青藏高原高寒草原近地表圈层N2O梯度及交换特征

深入了解N2O在不同生态系统土壤及大气中产生和交换特征对于全球气候变化研究具有重要意义.本研究重点探讨N2O在高寒草原近地表圈层中的产生及迁移过程机制.于2000年7月至2001年7月在青藏高原高寒草原地区从土壤1.5 m深到大气中32 m高度10个层次梯度进行N2O浓度变化的观测.结果显示,土壤和大气中N2O浓度均有明显的变化特征.大气中各个层次N2O的浓度都低于土壤中N2O浓度,此浓度差异直接导致了该地区高寒草原土壤向大气中排放N2O气体,其平均排放通量为0.05×10-4μmo1.m-2.s-1,但是在实验点上全年的观测中,N2O气体排放并没有表现出明显的季节性变化特征.土壤中N2O浓度随深度增加而不断升高,浓度最高值出现在1.5 m深处.进一步的分析表明,N2O浓度随深度递增主要是由环境因子中同样递增的土壤湿度所引起的.大气中不同梯度上N2O气体没有明显的浓度差异.近地表各个圈层中N2O浓度在季节上有非常相似的变化特征,即N2O高浓度均出现在入秋和深冬时节.除了N2O浓度变化在各个圈层之间显著相关以外,表层土壤中N2O浓度也与N2O排放变化有明显的相关关系,这表明浓度的差异是导致N2O气体排放变化的最直接因素.近地表土壤中N2O气体是土壤表层N2O气体排放的直接源泉,并且深层土壤中的N2O气体浓度高于浅层土壤,由此我们可以认定土壤中N2O气体通过微生物作用产生以后,由于浓度差异导致从深层土壤到浅层土壤的逐步扩散,最后经地表排放到大气当中去.     

青藏高原高寒草原碳排放及其迁移过程研究

采用箱式法通过对青海省五道梁地区高寒草原生态系统表层土壤含碳温室气体的研究发现 ,该地区高寒草原系统表层土壤 CO2 和 CH4 在 7～ 8月份的平均排放通量分别为 0 .46μmol· m- 2 · s- 1和 - 0 .43× 1 0 - 3μmol·m- 2 ·s- 1,此两种气体的排放通量随时间都有明显的变化特征 ,它们的日变化均为明显的单峰型 ,而且其中 CO2 排放通量的变化明显受大气温度变化的影响。地下土壤中 CO2 和 CH4 气体浓度随深度的增加呈递减趋势 ,进一步的分析表明这两种气体浓度在土壤中与相邻层次的气体浓度有很明显的相关关系 ,尤以永久冻土上层边界附近最为显著。     

内蒙古天然与放牧草原温室气体排放研究

采用静态箱-气相色谱法测定内蒙古典型草原温室气体排放。结果表明,四类天然草原吸收CH4、排放N2O和CO2各自有其相对固定的季节变化形式,四类草原和大气交换温室气体通量的变化形式基本一致,受年度气候变化所控制,而土壤、植被类型、降雨量等天然因素和放牧强度等人为因素仅影响排放强度。与天然羊草草原相比,自由放牧降低了羊草草原对CH4的吸收和N2O排放,增加了CO2的排放。     

中国农田土壤N2O排放通量分布格局研究

中国作为世界上一个重要农业大国,对全球大气中N2O浓度的影响正在引起人们的普遍关注.该研究采用针对农业土壤痕量气体排放估算建立的、基于N2O的产生、传输和消耗机理的反硝化分解(DNDC)模型,在建立了有关中国气候、农业土壤和农业生产的分县数据库基础上,估计了我国各县农业土壤N2O的排放通量,发现我国农田土壤N2O排放通量有较明显的地区差异,西北地区较低,东南地区较高.还发现无论温度升高,还是施肥量变化,对我国农田土壤N2O排放通量的影响,都存在区域差异,表现为东南地区的变化幅度较西北地区大,这可能与我国气候的干湿变化有较密切的关系.     

中国农田土壤N2O排放通量分布格局研究

中国作为世界上一个重要农业大国,对全球大气中N2O浓度的影响正在引起人们的普遍关注。该研究采用针对农业土壤痕量气体排放估算建立的,基于N2O的产生、传输和消耗机理的反硝化分解（DNDC）模型,在建立了有关中国气候、农业土壤和农业生产的分县数据库基础上,估计了我国各县农业土壤N2O的排放通量,发现我国农田土壤N2O排放通量有较明显的地区差异,西北地区较低,东南地区较高。还发现无论温度升高,还是施肥量变化,对我国农田土壤N2O排放通量的影响,都存在区域差异,表现为东南地区的变化幅度较西北地区大,这可能与我国气候的干湿变化有较密切的关系。     

全球森林土壤N2O排放通量的影响因子

森林生态系统在全球变暖格局下的地位和作用,尤其是土壤氮库对大气氮沉降增加的响应逐渐成为全球变化研究的热点。本文通过对已有文献资料的调研和整理,分析了1984—2009年间全球38个森林土壤N2O排放通量的野外原位观测结果的分布特征,评估了森林土壤N2O年排放累积通量对大气氮素沉降量和水热条件等因子变化的响应。结果表明,全球森林土壤N2O排放通量的平均值为0.47kgN·hm-2·a-1,而且土壤N2O释放通量随着纬度增加逐渐降低。作为一个复杂的生态过程,土壤N2O累积释放量同样受到年均温、年降水量以及土壤属性的显著影响。其中全球森林土壤N2O释放温度敏感性系数(Q10值)约为1.5。另外,森林土壤N2O排放通量也随着氮沉降量的增加而显著增大,大气氮沉降量可解释土壤N2O排放通量在不同区域之间53%的差异;土壤pH、年均温和大气氮沉降量可以解释区域森林土壤N2O排放通量变化的55%。     

长白山阔叶红松林土壤N2O排放通量的变化特征

采用静态密闭箱 /气相色谱分析方法对长白山阔叶红松林两个样地的N2 O排放通量进行了测定。结果表明 ,凋落物对林地土壤N2 O排放的影响是显著的 ,其对全年N2 O排放的平均贡献率是 36 89%。长白山阔叶红松林土壤是大气N2 O一个重要的源 ,但在极少的天气状况下也能吸收大气中的N2 O ,而起着汇的作用。其排放通量的变化范围是 - 4 1 4 8～ 2 91 84μgN2 O·m-2 ·h-1,平均通量是 6 8 7μgN2 O·m-2 ·h-1,高于其他类型林地的排放通量 ,且变动范围也较其他森林类型大。无凋落物林地土壤N2 O排放通量变化范围是 - 2 3 2 4～ 93 75 μgN2 O·m-2 ·h-1,平均通量为 33 79μgN2 O·m-2 ·h-1。两个样地N2 O排放通量的季节变化特征相似 :夏季N2 O的排放通量最高 ,春季次之 ,秋冬两季较低且趋于平稳。昼夜变化趋势也相似 :N2 O排放通量的最大值都出现在 18∶0 0 ,最小值都出现在 12∶0 0和 14∶0 0。研究还表明 ,林地土壤N2 O的排放通量与地表温度和地下 5cm温度的相关性较好 ,无凋落物的样地N2 O的排放通量仅与地下 5cm温度的相关性较好。     

塿土土壤剖面中N2O浓度的时间和空间变异

用土壤探头法对塿土玉米—小麦轮作体系下不同剖面层次N2O浓度变化进行了2a的田间原位监测。结果表明：塿土土壤剖面中N2O浓度具有较大的时间变异,表现为土壤N2O浓度在一年的不同时期变化较大,以温度高、水分充足的7—8月份为最高,温度较低的冬季最低;全年中土壤剖面中各层N2O浓度在降水或者灌溉后均有一个峰值。从空间上来看,土壤不同剖面层次的N2O浓度的变化以60cm土层最高,表层10cm最低,浓度在剖面中的变化顺序为10cm＜30cm＜150cm＜90cm＜60cm。2a的研究结果相比,降水量较高的1999年土壤剖面各层的N2O浓度较高。2a试验期间对照和施肥处理各土壤层次的变异系数分别为7．1％-29．4％和10．8％-50．9％,其中1999年变异系数分别为20．2％-29．4％和32．11％-50．9％,2000年分别为7．14％-18．4％和10．8％-25．9％。从变异系数上来看,1999年高于2000年;施肥处理高于对照;N2O浓度较高的下层土壤高于10cm表层土壤。两个处理N2O出现的时间和剖面变化趋势相同,但施肥处理各时期、各土层的浓度均高于对照。这些结果充分说明塿土土壤存在明显的反硝化N2O气态损失,施肥显著地增加了其产生量,深层土壤N2O的产生是塿土N2O的一个不容忽视的来源;N2O的产生和排放具有极大的时间和空间变异。     

氮沉降对森林土壤主要温室气体通量的影响

大气氮沉降已经并将继续对森林土壤主要温室气体(CO2、CH4和N2O)通量产生影响.综述了国内外氮沉降对森林土壤主要温室气体通量影响及其机理的研究现状.由于森林类型、土壤N状况、氮沉降量及沉降类型等不同,氮沉降对森林土壤主要温室气体通量的影响主要表现为抑制、促进和不显著3种效果.在N限制的森林中,氮沉降对土壤主要温室气体通量无显著影响,或促进土壤CO2排放;在"N饱和"的森林中,氮沉降可减少土壤CO2排放,抑制对大气CH4的吸收,增加N2O排放.分析了产生以上影响效果的作用机理,介绍了氮沉降对森林土壤主要温室气体通量影响的研究方法,探讨了该领域存在的问题及未来研究的方向.     

不同草地类型对三江源区草地土壤养分的影响

对三江源区原生高寒草甸草原、退化高寒草甸草原、退化高寒草原和人工草地4种不同草地类型中,草地土壤养分的含量进行了测定,结果表明;高寒草甸草原随着退化程度的加重,全氮、有效氮、全磷、有效磷、有效钾均在土壤表层含量降低,中下层土壤含量升高。原生高寒草甸草原全氮、全磷、有效磷含量在中层土壤含量升高,而有效氮、有效钾含量随着土层加深逐渐降低。退化高寒草原全氮、全磷含量随土层加深变化较不明显,有效氮在中层土壤含量较多随后急剧下降,有效磷和有效钾随土层加深逐渐减少。人工草地各种土壤养分均呈现随土层逐步下降的态势,总体来看,人工草地在表层土壤的各种养分含量远远大于原生和退化草地,土壤速效养分受退化程度影响较大,其变化幅度明显高于全量养分,表层土壤养分受退化影响的程度较深层土壤大。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.