Lamellar Thickness and Stretching Temperature Dependency of Cavitation in Semicrystalline Polymers

Polybutene-1 (PB-1), a typical semicrystalline polymer, in its stable form I shows a peculiar temperature dependent strain-whitening behavior when being stretched at temperatures in between room temperature and melting temperature of the crystallites where the extent of strain-whitening weakens with the increasing of stretching temperature reaching a minima value followed by an increase at higher stretching temperatures. Correspondingly, a stronger strain-hardening phenomenon was observed at higher temperatures. The strain-whitening phenomenon in semicrystalline polymers has its origin of cavitation process during stretching. In this work, the effect of crystalline lamellar thickness and stretching temperature on the cavitation process in PB-1 has been investigated by means of combined synchrotron ultrasmall-angle and wide-angle X-ray scattering techniques. Three modes of cavitation during the stretching process can be identified, namely “no cavitation” for the quenched sample with the thinnest lamellae where only shear yielding occurred, “cavitation with reorientation” for the samples stretched at lower temperatures and samples with thicker lamellae, and “cavitation without reorientation” for samples with thinner lamellae stretched at higher temperatures. The mode “cavitation with reorientation” occurs before yield point where the plate-like cavities start to be generated within the lamellar stacks with normal perpendicular to the stretching direction due to the blocky substructure of the crystalline lamellae and reorient gradually to the stretching direction after strain-hardening. The mode of “cavitation without reorientation” appears after yield point where ellipsoidal shaped cavities are generated in those lamellae stacks with normal parallel to the stretching direction followed by an improvement of their orientation at larger strains. X-ray diffraction results reveal a much improved crystalline orientation for samples with thinner lamellae stretched at higher temperatures. The observed behavior of microscopic structural evolution in PB-1 stretched at different temperatures explains above mentioned changes in macroscopic strain-whitening phenomenon with increasing in stretching temperature and stress-strain curves.     

大熊猫与同域动物在海拔分布上的生态位分化

大熊猫（Ailuropoda melanoleuca）是中国的特有物种,其成功放归可能受放归地气候、栖息地、同域动物等多种因素的影响。本研究在野外调查的基础上,基于生态位理论等方法,探讨了栗子坪国家级自然保护区大熊猫与其大中型同域动物的空间关系。调查结果表明,该保护区内大熊猫同域动物共20种,分别属于2纲5目,其中东洋型分布物种占优势（30%）。大熊猫同域动物分布海拔显著低于大熊猫的分布海拔（P＜0.05）,大熊猫分别与灵长目等5个目的动物在海拔分布上均存在显著的生态位分化（P＜0.001）。灵长目动物在空间分布上与大熊猫分布相异,而其他目的动物与大熊猫空间分布类似。偶蹄目动物痕迹数量占比最高（54.14 %）,而食肉目的小熊猫与大熊猫样线共同遇见率达到了43.75%。本研究结果表明,该地大熊猫同域动物较为丰富,在海拔分布上与大熊猫存在生态位分化。该研究可为圈养大熊猫的放归提供参考依据。     

Herbaceous layer determines the relationship between soil respiration and photosynthesis in a shrub-dominated desert plant community

Plant and Soil - Although the linkages between aboveground photosynthates production and belowground respiration processes have been well studied, doubts remain as to the extent that photosynthate...     

梭梭幼苗的存活与地上地下生长的关系

近几十年来,全球气候变化以及人类活动的加剧,导致古尔班通古特南缘荒漠地区的降水与地下水位发生显著的改变,这些改变必然导致荒漠植物用水策略的适应性变化。以古尔班通古特沙漠南缘原始沙漠中建群种梭梭的1年生幼苗为研究对象,对气象因子、土壤含水率、梭梭幼苗死亡率、地上地下高度(深度)、面积、生物量状况进行了全生长期的连续监测,以期探明1年生梭梭的生长、生存规律。结果表明:梭梭幼苗在土壤水分较为充沛的4—6月生长迅速,但随着土壤水分的消耗,7月地上地下部分都出现了不同程度的萎缩,在8月又恢复生长。在全年生长期中,幼苗死亡率基本呈现逐月下降的趋势。这说明在干旱来临前,梭梭幼苗快速生长以抢占更多资源;当遭遇干旱时,幼苗通过同化枝凋落有效的维持了根系供水与地上部分需水之间的平衡,保证了存活同化器官的光合能力,从而降低了死亡率。同时,幼苗以牺牲地上部分生长为代价将更多的光合产物转向根系,使得幼苗能够获得更多的水分保证其生长、生存。     

Change in ecological stoichiometry of Carex brevicuspis in response to seasonal dynamics and elevation in Dongting Lake,China

Plant nutrient stoichiometry is affected by both environmental factors and plant physiological processes. However, we know little about how small elevation gradients (influencing e.g. flooding regimes) and seasonality combine with soil physicochemical properties to influence nutrient stoichiometry in wetland plants. In this study, we examined these factors in Carex brevicuspis at Dongting Lake, China, during the non‐flooding periods in March, May and December of 2015 and February of 2016. We found that total foliar C concentration increased as elevation increased, especially during December 2015 and February 2016. At the low‐elevation site, total foliar C concentration decreased over the season, whereas it first increased and then decreased over time at higher elevations. Foliar total N and P concentrations decreased from March to May and subsequently increased throughout the season, and these concentrations were always much higher at the low‐elevation site. The C:N and C:P ratios first increased and then decreased over the season, while increasing with rising elevation. The N:P ratio was lower at the low‐elevation site, especially during May 2015 and February 2016; its variation over time differed across the elevations. A canonical correspondence analysis revealed that soil organic C, total N and soil nitrate N are important for determining C. brevicuspis stoichiometry. Our results suggest that both elevation and plant life stage have a significant influence on plant stoichiometry. This study improves our understanding of the seasonal dynamics of plant nutrients under different geographical conditions.     

In vitro expression and monoclonal antibody of RNA-dependent RNA polymerase for infectious bursal disease virus

VP1, the RNA-dependent RNA polymerase of infectious bursal disease virus (IBDV), has been suggested to play an essential role in the replication and translation of viral RNAs. In this study, we first expressed the complete VP1 protein gene in Escherichia coli (E. coli), and then the produced polyclonal antibody and four monoclonal antibodies (mAbs) to recombinant VP1 protein (rVP1) were shown to bind the IBDV particles in chicken embryo fibroblast and Vero cells. The epitopic analysis showed that mAbs 1D4 and 3C7 recognized respectively two distinct antigenic epitopes on the rVP1 protein, but two pair of mAbs 1A2/2A12 and 1E1/1H3 potentially recognized another two topologically related epitopes. Immunocytochemical stainings showed that VP1 protein formed irregularly shaped particles in the cytoplasm of the IBDV-infected cells. These results demonstrated that the mAbs to rVP1 protein could bind the epitopes of IBDV particles, indicating that the rVP1 protein expressed in E. coli was suitable for producing the mAb to VP1 protein of IBDV, and that the cytoplasm could be the crucial site for viral genome replication of IBDV.     

Development of array-based technology for detection of HAV using gold-DNA probes

A sensitive method for detection of Hepatitis A virus (HAV) by utilizing gold-DNA probe on an array was developed. Amino-modified oligodeoxynucleotides at the 5' position were arrayed on an activated glass surface to function as capture probes. Sandwich hybridization occurred among capture probes, the HAV amplicon, and gold nanoparticlesupported oligonucleotide probes. After a silver enhancement step, signals were detected by a standard flatbed scanner or just by naked eyes. As little as 100 fM of HAV amplicon could be detected on the array. Therefore, the array technology is an alternative to be applied in detection of HAV due to its low-cost and high-sensitivity.     

三江源国家公园游憩承载力模拟仿真研究

游憩承载力评估与预测是国家公园游憩规划与动态管理的重要工具。采用系统动力学模拟仿真软件Vensim＿PLE,构建三江源国家公园游憩承载力系统动力学模型,包括资源空间、生态环境、社会经济、社会心理4个子系统。以2015—2035年为系统仿真区间,模拟了原始情景、社会驱动模式、生态保护优先模式、协调发展模式4种情景下各子系统的发展演化趋势,为三江源国家公园游憩规划与管理提供参考。结果表明：(1)原始情景模式下,三江源国家公园游憩承载力呈先增后降的趋势,在2031年面临游憩承载力超载风险,在加大游憩设施投入的社会驱动模式下,游憩承载力将有所提升,但2031年后提升效果微弱。(2)生态保护优先模式通过提高污染治理能力和适度控制游客规模,游憩承载力有所提升,并将游憩承载力超载风险由2031年延迟至2033年。(3)协调发展模式下,生态环境承载力和资源空间承载力缓慢上升,在4种模式中均为最高值,游憩承载力也达到最大值,游憩承载力超载的风险由2031年延长至2035年以后。对国家公园游憩承载力的模拟预测,可为合理及时调控提供科学参考,有利于三江源国家公园生态保护与游憩质量提升。     

胃饥饿素对小鼠急性肺损伤的保护作用及其机制研究

目的探讨胃饥饿素对小鼠急性肺损伤的保护作用和机制。方法将60只小鼠采用随机数字表法分为6组:对照组、模型组、胃饥饿素低、中、高剂量组和地塞米松组。对照组和模型组腹腔注射0.2 mL生理盐水,胃饥饿素各组分别注射400、200、100 μg/ kg溶液,地塞米松组注射2 mg/kg。给药后1 h,对照组滴注等体积生理盐水,其余各组鼻腔滴入10 μg (20 μL)脂多糖 (LPS)。24 h后,测量肺湿/干重 (W/D),ELISA测量支气管肺泡灌洗液 (BALF)中肿瘤坏死因子 (TNF)-α、白细胞介素 (IL)-6和血清中TNF-α、IL-6和IL-1β含量,苏木精-伊红染色检测肺组织病理学形态,蛋白免疫印迹法测量肺组织中IL-1β p17、半胱氨酸天冬氨酸蛋白酶-1 (caspase-1) p20、Nod样受体家族3 (NLRP3)和消皮素 (GSDMD)蛋白表达。体外培养肺泡巨噬细胞,分为对照组、LPS+三磷酸腺苷 (ATP)组、低、中和高剂量胃饥饿素组。碘化吡啶 (PI)染色观察细胞焦亡,蛋白免疫印迹法检测细胞中IL-1β p17、 caspase-1 p20、NLRP3和GSDMD蛋白表达。多组间比较采用单因素方差分析,组间两两比较采用LSD-t检验。结?果与对照组比较,模型组肺W/D (4.03±0.46比12.71±0.68)、BALF中TNF-α (3.92±0.59比12.83±0.66)、IL-6 (23.94±3.51比159.03±5.21)、血清中TNF-α (2.67±0.29比13.23±0.76)、IL-6 (26.73±2.61比141.64±3.86)和IL-1β (43.89±4.19比249.03±5.38)含量升高,肺组织IL-1β p17 (0.67±0.02比0.93±0.02)、caspase-1 p20 (0.67±0.04比1.02±0.08)、NLRP3 (0.58±0.04比0.91±0.03)和GSDMD蛋白表达 (0.46±0.06比1.06±0.09)上调,差异具有统计学意义 (P均< 0.05)。与模型组比较,低、中和高剂量胃饥饿素组和地塞米松组肺W/D (12.71±0.68比11.13±0.53,7.56±0.31,6.12±0.32,6.14±0.34)、BALF中TNF-α (12.83±0.66比9.89±0.47,9.78±0.53,7.33±0.27,6.27±0.38)、IL-6 (159.03±5.21比130.32±2.49,122.87±3.31,67.42±1.70,56.45±3.33)以及血清中TNF-α (13.23±0.76比10.14±0.52,9.04±0.46,6.43±0.38,6.35±0.26)、IL-6 (141.64±3.86比121.89±3.34,116.42±2.68,71.23±3.02,78.54±5.13)和IL-1β含量 (249.03±5.38比230.14±5.53,196.53±6.41,100.67±3.50,91.56±4.29)呈浓度依赖性减低,肺组织IL-1β p17 (0.93±0.02比0.84±0.01,0.71±0.02,0.61±0.04,0.60±0.02)、caspase-1 p20 (1.02±0.08比0.90±0.03,0.81±0.02,0.63±0.03,0.61±0.03)、NLRP3 (0.91±0.03比0.85±0.03,0.68±0.05,0.64±0.02,0.68±0.03)和GSDMD蛋白表达 (1.06±0.09比0.71±0.02,0.75±0.02,0.67±0.03,0.61±0.01)呈浓度依赖性下调,差异具有统计学意义 (P均 < 0.05)。与对照组比较,LPS+ATP组PI阳性细胞数增加,细胞肿胀和膜破裂,肺泡巨噬细胞中IL-1β p17 (0.44±0.01比0.99±0.03)、caspase-1 p20(0.37±0.01比1.32±0.02)、NLRP3 (0.39±0.02比1.31±0.01)和GSDMD表达 (0.39±0.01比0.83±0.02)上调,差异具有统计学意义 (P均 < 0.05)。与LPS+ATP组比较,低、中和高剂量胃饥饿素组PI阳性细胞数呈剂量依赖性减少,细胞肿胀和膜破裂缓解,肺泡巨噬细胞中IL-1β p17 (0.99±0.03比0.55±0.02,0.45±0.02,0.31±0.02)、caspase-1 p20 (1.32±0.02比0.45±0.02,0.42±0.02,0.09±0.01)、NLRP3 (1.31±0.01比0.90±0.02,0.82±0.02,0.33±0.01)和GSDMD (0.83±0.02比0.67±0.04,0.49±0.01,0.35±0.02)表达呈剂量依赖性下调,差异具有统计学意义 (P 均 < 0.05)。结论胃饥饿素对小鼠急性肺损伤具有保护作用,该作用可能与NLRP3炎性小体介导炎症反应和肺泡巨噬细胞焦亡有关。