脉冲式降水对不同类型草地土壤微生物呼吸碳释放量的影响

降水事件引起土壤短时间内释放大量CO_2的现象常称为降水脉冲效应。降水事件发生后,由于水分和养分可获得性快速提升使土壤微生物呼吸速率快速升高至正常水分状况的数倍,从而导致土壤CO_2大量释放并一定程度上影响着生态系统碳循环过程和土壤碳平衡,尤其在干旱或半干旱地区。利用自主研发的能快速测定土壤微生物呼吸速率的装置,对内蒙古三类典型草原(草甸草原、典型草原和荒漠草原)土壤分别开展土壤复湿实验(60%饱和含水量),并采用高频测定(48 h测定288次)。在土壤复湿后在所有温带草地类型中均发生了明显的脉冲效应,降水脉冲过程中单位有机质(土壤有机碳,SOC)最大呼吸速率(R_(SOC-max))整体表现为荒漠草原(1.59 mg C g~(-1) SOC h~(-1))草甸草原(0.73 mg C g~(-1) SOC h~(-1))典型草原(0.50 mg C g~(-1) SOC h~(-1));而脉冲效应的持续时间(Duration)则表现为典型草原(2.5 h)草甸草原(1.5 h)荒漠草原(0.67 h)。在土壤复湿48 h内,单位土壤微生物呼吸累积量(A_(R_(Soil)))的大小规律与单位土壤微生物呼吸速率R_(Soil)一致,均为典型草原草甸草原荒漠草原;然而,如果用土壤有机质进行标准化,单位有机质呼吸累积量A_(R_(SOC))表现为荒漠草原(9.74 mg C g~(-1) SOC)典型草原(6.54 mg C g~(-1) SOC)草甸草原(3.54 mg C g~(-1) SOC),与当地年降雨频率呈负相关关系,表明降水脉冲效应与土壤长期经历的干旱状况存在密切关系。本研究结果不仅证明在干旱半干旱区域降水脉冲效应的普遍性,同时还启发我们应从国家或区域尺度开展研究,以进一步揭示土壤基质含量、土壤干旱状况等对降水脉冲效应的影响。     

老年慢性心力衰竭患者甲状腺激素水平与认知功能、心功能及心血管事件的关系研究

摘要 目的：探讨老年慢性心力衰竭（CHF）患者甲状腺激素（TH）水平与认知功能、心功能及心血管事件的关系。方法：将我院2018年6月～2020年6月收治的140例老年CHF患者纳入研究,检测患者TH指标[血清三碘甲状腺原氨酸（T₃）、游离三碘甲状腺原氨酸（FT₃）、甲状腺素（T₄）、游离甲状腺素（FT₄）、促甲状腺激素（TSH）]水平。按蒙特利尔认知评估量表（MoCA）评分将患者分为认知障碍组（MoCA评分＜26分）、非认知障碍组（MoCA评分≥26分）,比较两组各TH指标与MoCA评分。比较不同纽约心脏病协会（NYHA）分级患者的TH指标与心功能指标[左室射血分数（LVEF）、左室舒张末期内径（LVEDD）、左室收缩末期内径（LVESD）]。根据患者住院期间是否发生心血管事件分为心血管事件组和非心血管事件组,比较两组各TH指标。经Pearson线性相关分析TH指标与MoCA评分、心功能指标的相关性。结果：认知障碍组血清T₃、FT₃水平及MoCA评分较非认知障碍组明显降低（P＜0.05）。Ⅲ级、Ⅳ级组的血清T₃、FT₃水平及LVEF较Ⅰ级、Ⅱ级组显著降低,其中Ⅳ级组低于Ⅲ级组（P＜0.05）。Ⅲ级、Ⅳ级组的LVEDD、LVESD较Ⅰ级、Ⅱ级组明显升高,且Ⅳ级组高于Ⅲ级组（P＜0.05）。心血管事件组血清T₃、FT₃水平较非心血管事件组显著降低（P＜0.05）。Pearson线性相关分析显示：血清T₃、FT₃水平与MoCA评分、LVEF呈正相关（均P＜0.05）,与LVEDD、LVESD呈负相关（均P＜0.05）。结论：老年CHF患者血清T₃、FT₃水平下调与其认知功能、心功能降低及心血管事件的发生密切相关,通过检测其血清T₃、FT₃水平,有利于进一步了解其病情变化。     

Effects of pulse precipitation on soil organic matter mineralization in forests: spatial variation and controlling factors

脉冲降水对森林中土壤有机物矿化的影响：空间变化和控制因素 降水脉冲效应使土壤有机物在短时间内迅速分解并释放大量CO₂到大气中。降水脉冲效应对生态系统的碳循环和土壤碳平衡的研究具有十分重要的意义,但它在森林土壤中的空间变化和基本机制仍不清楚。我们采集中国东部22个典型森林生态系统的土壤样品(0–10cm),研究模拟脉冲降水对土壤微生物呼吸速率的影响。模拟降水脉冲使土壤样品达到65%饱和含水量,以分钟为单位测量R_s,持续48 小时。研究结果显示,降水脉冲可以使微生物呼吸速率迅速增加1.70–38.12倍。微生物最大呼吸速率 (R_s-soil-max)、碳释放总量R_s (A_Rs-soil)和达到呼吸峰值的时间(T_Rs-soil-max)在不同的土壤中存在显著差异。此外,不同 气候区的脉冲效应也有明显不同。中温带的R_s-soil-max (11.701 µg C g⁻¹ soil h⁻¹)和A_Rs-soil (300.712 µg C g⁻¹ soil)最高。土壤化学特性(总碳和总氮、pH值和氧化还原电位)和土壤粒径与森林土壤的脉冲效应密切相关,但土壤微生物的贡献较小。我们的研究结果表明,在大尺度范围内,脉冲变化短期内增加森林土壤中CO₂的排放,并揭示了对这种变化影响最大的因素。这些发现为未来对森林生态系统的碳循环和调节全球生态系统碳循环的研究提供科学数据支持。     

卵巢早衰患者血清抑制素B、抗苗勒管激素及性激素水平与子宫动脉血流参数的相关性研究

目的:探讨卵巢早衰(POF)患者血清抑制素B(INHB)、抗苗勒管激素(AMH)及性激素水平与子宫动脉血流参数的相关性。方法:选择2018年5月至2020年5月期间我院收治的126例POF患者(POF组)和同期于我院进行体检的85例健康女性志愿者(对照组)。检测所有研究对象血清INHB、AMH以及促黄体生成素(LH)、促卵泡激素(FSH)、雌二醇(E2)水平,经阴道多普勒超声检测子宫动脉血流参数[收缩期峰值流速(PSV)、舒张末期流速(EDV),血流阻力指数(RI)、搏动指数(PI)]。Pearson相关性分析POF患者血清INHB、AMH、LH、FSH、E2水平与PSV、EDV、RI、PI的相关性。结果:POF组血清INHB、AMH、E2水平、PSV、EDV低于对照组(P<0.05),LH、FSH水平、RI、PI高于对照组(P<0.05)。Pearson相关性分析结果显示POF患者血清INHB、AMH、E2水平与PSV、EDV呈正相关(P<0.05),与RI、PI呈负相关(P<0.05),LH、FSH与PSV、EDV呈负相关(P<0.05),与RI、PI呈正相关(P<0.05)。结论:POF患者血清INHB、AMH、E2水平降低,LH、FSH水平升高,血清INHB、AMH和性激素与子宫动脉血流受限有关。     

Evidence for the Addition of the Superoxide Anion to the Anti-Oxidant n-Propyl Gallate in Aqueous Solution

n-Propyl gallate reacts with the superoxide radical anion in aqueous solution (k = 5.1 × 10⁵ mol^?1 dm³s^?1). The spectrum of the transient species so formed has been measured (absorbance maximum at 550nm, ? = 1360mol^?1dm³cm^?1). Electron or H atom transfer processes as well as proton abstraction have been excluded as possible mechanisms, and it is proposed that an addition reaction takes place.     

Determination of the Superoxide Dismutase-Like Activity of Cimetidine-Cu(II) Complexes

Using the direct method of pulse radiolysis to determine the superoxide dismutase like activity of copper(II) cimetidine complexes, it was found that the reaction rate constant with O^?₂, k_cat, was (8.5 ± 0.5) × 10⁸ M^?1s^?1 independent of the cimetidine concentrations present in excess of 50–200 μM over the metal. The results suggest that either the 1:1 ligand to metal complex does not catalyze O^?₂ dismutation at a comparable rate to that of the 2:1 complex, or that the stability constant of the last species is much higher than that determined earlier by Kimura el al.,¹ and only the 2:1 species is present in the solutions. With the indirect methods of cytochrome c and NBT for determining the ability of these complexes to catalyze O^?₂ dismutation, these compounds exhibited a much lower SOD activity. and k_cat was determined to be (5.0 ± 0.3) × 10⁶ and (7.± 0.4) × 10¹ M^?1s^?1. respectively using the two assays.     

Persistent versus transient tree encroachment of temperate peat bogs: effects of climate warming and drought events

Peatlands store approximately 30% of global soil carbon, most in moss‐dominated bogs. Future climatic changes, such as changes in precipitation patterns and warming, are expected to affect peat bog vegetation composition and thereby its long‐term carbon sequestration capacity. Theoretical work suggests that an episode of rapid environmental change is more likely to trigger transitions to alternative ecosystem states than a gradual, but equally large, change in conditions. We used a dynamic vegetation model to explore the impacts of drought events and increased temperature on vegetation composition of temperate peat bogs. We analyzed the consequences of six patterns of summer drought events combined with five temperature scenarios to test whether an open peat bog dominated by moss (Sphagnum) could shift to a tree‐dominated state. Unexpectedly, neither a gradual decrease in the amount of summer precipitation nor the occurrence of a number of extremely dry summers in a row could shift the moss‐dominated peat bog permanently into a tree‐dominated peat bog. The increase in tree biomass during drought events was unable to trigger positive feedbacks that keep the ecosystem in a tree‐dominated state after a return to previous ‘normal’ rainfall conditions. In contrast, temperature increases from 1 °C onward already shifted peat bogs into tree‐dominated ecosystems. In our simulations, drought events facilitated tree establishment, but temperature determined how much tree biomass could develop. Our results suggest that under current climatic conditions, peat bog vegetation is rather resilient to drought events, but very sensitive to temperature increases, indicating that future warming is likely to trigger persistent vegetation shifts.     

Application of two SH-based methods for metallothionein determination in mussels and intercalibration of the spectrophotometric method: laboratory and field studies in the Mediterranean Sea

Metallothionein (MT) induction is widely used as a biomarker of exposure to metals in mussels. The aims of the present work were first to compare the suitability of spectrophotometry and differential pulse polarography (DPP) for MT detection in mussels exposed to 200 ppb cadmium for 9 days in a laboratory experiment and in mussels sampled in different seasons from expected pollution gradients along the Mediterranean Sea; second, to intercalibrate the widely used spectrophotometric method using mussels from Saronikos Gulf. In the intercalibration of the spectrophotometric method, similar results (p>0.05) were obtained by two different research teams indicating a good reproducibility of the technique. However, polarographic and spectrophotometric methods gave significantly (p<0.05) different results in laboratory and field studies. In the laboratory experiment, MT values detected with DPP were nine times higher than with spectrophotometry. The results obtained by the two methods were significantly correlated. Both methods could discriminate between control and exposed mussels. In field studies, MT values obtained by DPP were 34–38-fold higher than with spectrophotometry, and MT concentrations measured by both methods were not correlated. This discrepancy could be due to several factors, including the low levels of bioavailable metals in the studied areas and the possibility that the different methods can measure MT isoforms differentially. Further work is needed to decipher the functions of MT isoforms in mussels. This information is relevant for the application of MT as a biomarker in biomonitoring programmes.     

Demonstration of biofilm removal from type 304 stainless steel using pulsed-waveform electropolishing

Abstract

This article describes an electrochemical method to remove bacterial biofilm from a stainless steel (SS) surface using a potential pulse/reverse pulse technique. This technique employs a periodic waveform that consists of anodic and cathodic pulses. The pulses can effectively strip a thin layer of metal off the SS surface, along with the adherent biofilm, in a saline solution. Not only can the pulses effectively remove biofilm from the SS surface, but they also regenerate the original mirror-like shiny surface. The importance of this electrochemical biofilm removal method is its wide applicability for any types of biofilms. That is, instead of directly removing the biofilm, it removes a very thin layer of the metal under the biofilm. Thus, the removal process is independent to the nature of the biofilms. Furthermore, this electrochemical biofilm removal method is rapid (less than 30?s of potential pulse time) and does not require hazardous chemicals.