热棒位置与热棒效果关系的研究

热棒主要是在冬季将地下的热通过热棒导向大气,使冻土范围和冻土上限都变大,这样使冻土路基更加稳定.由于热棒只能影响一定的区域,所以热棒的埋设位置对热棒保护路基土有很大的影响,本文通过MRDT600温度监测系统对埋设直插型热棒的试验路路基与埋设了斜插型热棒的试验路路基进行温度监测.通过对监测的温度数据进行分析和对比,总结直棒、斜棒与L型热棒在保护冻土路基方面的优缺点.     

Drying–rewetting cycles release phosphorus from forest soils

Drying–rewetting cycles (D/W) occur frequently in topsoils and may mobilize phosphorus (P). We investigated the effect of repeated D/W on the release of dissolved inorganic (DIP) and organic P (DOP) from forest floors and A horizons. Samples were taken from 3 European beech sites and from 3 Norway spruce sites. Soils were desiccated up to pF 6 (–100 MPa) in three D/W cycles in the laboratory, while the controls were kept permanently at 50% water holding capacity. After each drying, P was extracted from the soils in water. D/W caused the release of DIP and DOP especially from O layers. There was no general difference in response to D/W between samples from beech and spruce. The net release of DIP after D/W was largest from the Oe horizons (average 50–60 mg P kg^?1) for both beech and spruce forest soils. The net release of DIP from Oi layers was on average 7.8 mg P kg^?1 and from spruce Oa layers 21.1 mg P kg^?1. In the A horizons, net DIP release was similar in beech and spruce soils with 0.4 mg P kg^?1. The release of DOP was less than the release of DIP except for the A horizons. Repeated cycles did not increase the release of DIP and DOP. The release of DIP and DOP was positively correlated with the microbial biomass in Oe and Oa layers but not in Oi layers. Our results suggest that D/W may significantly influence the short term availability of dissolved P in both beech and spruce forest soils.     

五垒岛湾海域无机氮、无机磷的时空分布和氮磷比值变化

根据2012-2014年5月、10月的调查数据,分析了五垒岛湾海水中无机氮、无机磷的时空分布特征和N/P比值的变化。结果表明,该海域水体中无机氮、无机磷平均含量分别为0.202mg/L和0.011mg/L,达国家二类水质标准,均表现出逐年增加的趋势;空间分布上表现出近岸水域含量大于远岸的变化趋势,原因可能是受陆源物质输入的影响所致;除少数站位外,该海域N/P比值接近16∶1,并表现出逐年增大的趋势,但春季可能受到赤潮的威胁。     

凡纳滨对虾精养池养殖水体的富营养状况时空差异

监测了凡纳滨对虾养殖全过程精养虾池养殖水体中溶解态无机氮(DIN)、溶解态活性磷酸盐(DIP)、水体的化学需氧量(COD)、pH、溶解氧(DO)、营养状态综合指数(E)等理化指标的变化,以及养殖后期水体中各理化因子的水平、垂直分布。结果表明:在凡纳滨对虾养殖过程中,DIN质量浓度为(0.093±0.076)～(1.736±1.134)mg·L–1,DIP质量浓度为(0.062±0.271)～(0.380±0.276)mg·L–1,COD质量浓度为(0.940±0.934)～(9.653±1.317)mg·L–1,E:(1.198±4.250)～(1267.537±68.534),富营养化程度随着养殖时间的增加逐渐增强,20d时各项指标均达到较大值,之后逐渐降低,到养殖后期又逐渐增强,营养状态综合指数(E)达到最大值;养殖后期,富营养化程度在水平方向随着靠近排污口的方向逐渐增强,营养状态综合指数(E):(343.230±1.659)～(2786.072±55.241),在垂直方向随着靠近池底的方向逐渐增强,营养状态综合指数(E):(2046.687±5.568)～(2789.524±7.166)。     

Changes of Soil Phosphorus Fractionation According to pH in Red Soils of China: An Incubation Experiment

Phosphorus (P) deficiency is one of the main problems limiting crop growth in red soils of southern China. The primary objective of this study was to examine P availability as a function of soil acidity. Soils were sampled from a long-term fertilization experiment and are referred as low-P (No P fertilization) and high-P (120 kg P₂O₅ ha^–1). Both low-P and high-P treatments were incubated adjusting soil pH to seven levels from 3.0 to 6.5 for 10, 20, 30 and 45 days. The pH, DIP, and Olsen-P were determined after each incubation period, and inorganic P fractions were measured at the end of incubation. For both low-P and high-P treatments, DIP decreased with rising pH value and increased with decreasing soil pH. Olsen-P, Ca-P (Ca₂-P, Ca₈-P, and Ca₁₀-P) and Al-P increased significantly with soil pH in low-P treatment. In high-P, Olsen-P increased with pH between 3.4 and 5.0 and was stable at higher pH. Moreover, Ca-P and Al-P increased significantly but Fe-P decreased with soil pH increase. The redundancy analysis showed that Ca-P, Al-P, and pH had positive effects on Olsen-P, but Occluded-P showed a negative correlation with Olsen-P in both soils. Our results confirmed that soil P availability was influenced by pH and that the changes in DIP and Olsen-P were linked to changes of inorganic fractions from occluded to Ca- and Al-bound forms. Managing soil acidity is a key issue regarding the availability of P in red soils of China and our results suggest that at least a pH of 5.0 should be targeted.     

MAGIC ANGLE EFFECT IN NORMAL COLLATERAL LIGAMENTS OF THE DISTAL INTERPHALANGEAL JOINT IN HORSES IMAGED WITH A HIGH-FIELD MAGNETIC RESONANCE IMAGING SYSTEM

Distal forelimb specimens of eight skeletally mature horses were imaged using proton density turbo spin echo, T1-weighted spoiled gradient echo, T2^*-weighted gradient echo, short tau inversion recovery and T2-weighted fast spin echo sequences with the limb parallel to the main magnetic field, and with angulation of the limb relative to the main magnetic field. The magic angle effect can be identified in the collateral ligaments of the distal interphalangeal joint when imaged in a high-field magnetic resonance (MR) imaging system with a horizontally oriented main magnetic field. This effect has previously been described in the collateral ligaments of the distal interphalangeal joint in a low-field system with a vertically oriented main magnetic field. The curvature of the ligaments places the fibers at the magic angle in both horizontally and vertically orientated main magnetic fields. This effect can be identified on short time of echo sequences and impacts the signal pattern of the ligaments at the level of the middle phalanx with the limb in a neutral position and with angulation of the limb. Magic angle effect should be considered as a possible cause of an asymmetrical signal pattern, depending on the positioning of the limb and the sequences used for imaging, when evaluating the collateral ligaments of the distal interphalangeal joint on images acquired with a high-field MR imaging system that has a horizontally oriented main magnetic field.     

催乳复合物、胰岛素样生长因子-Ⅰ对奶牛乳腺上皮细胞中AKT-1和mTOR表达的作用

信号转导分子AKT-1、mTOR对于乳腺上皮细胞中乳蛋白的转录和翻译至关重要,胰岛素、地塞米松和催乳素组成的催乳复合物(DIP)是包括AKT-1/mTOR在内的多种泌乳信号途径激活的必要条件。采用qRT-RCR和Western blotting分别检测不同培养时间点奶牛乳腺上皮细胞AKT-1、mTOR的mRNA和蛋白质水平表达情况,结果显示,在DIP培养条件下,AKT-1和mTOR表达量均上升。添加胰岛素样生长因子-Ⅰ(IGF-Ⅰ)后进一步促进了AKT-1 mRNA和蛋白质的表达;同时,mTOR mRNA和蛋白质水平的表达也增加,且均有显著差异(P<0.05),结果表明DIP存在时,IGF-Ⅰ上调AKT-1和mTOR的表达,增强了AKT/mTOR途径。