Sex differences in mass loss rate and growth efficiency in Antarctic fur seal (Arctocephalus gazella) pups at Macquarie Island

We investigated the relationship between the mass gained by a pup during a period of maternal attendance (as an index of milk intake) and the duration of the preceding foraging trip in relation to the mass-specific rate of mass loss during fasting periods and the growth rate of Antarctic fur seal (Arctocephalus gazella) pups at Macquarie Island. We found that (1) serially weighed male pups grew significantly faster than females pups and that (2) fasting female pups lost mass at a significantly higher rate (2.55% day⁻¹) than male pups (2.12% day⁻¹) of the same mass; (3) during periods of maternal attendance, there were no intersexual differences in the amount of mass gained by pups of the same size, hence (4) female pups required a higher daily mass gain to grow at the same rate as male pups. Our results show that intersexual differences in growth rate may be accounted for by intersexual differences in mass-specific rate of mass loss, because females lost 0.42% more of their total mass per day (i.e. 4.2 g kg⁻¹ day⁻¹) compared with male pups of the same body mass. Despite intersexual differences in growth rates, our results indicate equality of maternal expenditure between the sexes. Intersexual differences in the rate of mass loss may be due to differences in the metabolic rate, activity level and/or body composition of male and female pups. Received: 19 August 1998 / Received in revised form: 19 April 1999 / Accepted: 19 April 1999     

典型行业再利用土壤重金属含量分布、来源解析及生态风险评价

为深入探究典型行业再利用土壤重金属污染特征及生态风险状况,基于上海市嘉定区49个地块315个不同深度剖面土壤样品数据,采用地累积指数和潜在生态风险指数评估Cd、Pb、Cu、Zn、Ni、Hg和As这7种重金属含量特征和潜在生态风险程度,并利用源解析受体模型（APCS-MLR）和正定矩阵因子分解模型（PMF）解析其污染来源.结果表明：①研究区土壤中除As外,其余重金属均不同程度超过上海市土壤背景值,表层土壤中Cd、Pb、Cu、Zn、Ni和Hg含量分别是背景值的3.54、2.34、2.91、1.20、3.75和4.40倍;7种重金属含量随着土壤垂直剖面深度的增加逐渐降低,重金属在表层土壤中存在一定程度的富集,人类活动影响了重金属在土壤中的分布规律.②研究区内APCS-MLR和PMF两种受体模型均识别出土壤重金属4种主要来源,源1（Cu、Zn和Pb）为金属制品和汽车制造混合源,源2（Ni和Cd）为电镀企业来源,源3（Hg）主要为化工企业来源,源4（As）为自然源,两种受体模型结合运用,进一步提高源解析的精准度和可信度.③地累积指数由大到小表现为：Hg（1.54）>Ni（1.32）>Cd（1.21）>Cu（0.96）>Pb（0.64）>Zn（-0.33）>As（-1.02）;潜在生态风险指数结果显示,研究区综合潜在生态风险指数RI值在32.50~4 910.97,均值为321.40,整体呈现较强潜在生态风险,再开发利用工业场地土壤中重金属Hg、Ni和Cd的污染值得进一步关注.     

Potassium carbonate-based ternary transition temperature mixture (deep eutectic analogues) for CO2 absorption: Characterizations and DFT analysis

•Addition of hindered amine increased thermal stability and viscosity of TTTM. •Addition of hindered amine improved the CO₂ absorption performance of TTTM. •Good the CO₂ absorption of recycled solvents after two regenerations. •Important role of amine group in CO₂ absorption of TTTM confirmed by DFT analysis. Is it possible to improve CO₂ solubility in potassium carbonate (K₂CO₃)-based transition temperature mixtures (TTMs)? To assess this possibility, a ternary transition-temperature mixture (TTTM) was prepared by using a hindered amine, 2-amino-2-methyl-1,3-propanediol (AMPD). Fourier transform infrared spectroscopy (FT-IR) was employed to detect the functional groups including hydroxyl, amine, carbonate ion, and aliphatic functional groups in the prepared solvents. From thermogravimetric analysis (TGA), it was found that the addition of AMPD to the binary mixture can increase the thermal stability of TTTM. The viscosity findings showed that TTTM has a higher viscosity than TTM while their difference was decreased by increasing temperature. In addition, Eyring’s absolute rate theory was used to compute the activation parameters (ΔG*, ΔH*, and ΔS*). The CO₂ solubility in liquids was measured at a temperature of 303.15 K and pressures up to 1.8 MPa. The results disclosed that the CO₂ solubility of TTTM was improved by the addition of AMPD. At the pressure of about 1.8 MPa, the CO₂ mole fractions of TTM and TTTM were 0.1697 and 0.2022, respectively. To confirm the experimental data, density functional theory (DFT) was employed. From the DFT analysis, it was found that the TTTM+ CO₂ system has higher interaction energy (|ΔE |) than the TTM+ CO₂ system indicating the higher CO₂ affinity of the former system. This study might help scientists to better understand and to improve CO₂ solubility in these types of solvents by choosing a suitable amine as HBD and finding the best combination of HBA and HBD.     

可控震源振动器系统不确定性分析

为了解决可控震源施工过程中振动器系统的安全性问题,采用故障树法建立仿真 模型。通过失效分析得出各故障单元的失效模式及单元间分布规律,计算出振动器系统 的可靠度。开展对该系统敏感性的不确定性分析,得出影响振动器系统可靠性的关键因 素为重锤上部密封失效。采用有限元法对其应力场进行模拟仿真。结果表明:随着工作 频率的升高,O形圈应力波动越大,密封越容易失效。Von Mises应力随压缩率的增大先 减小后增大,随槽口半径的增大而增大;接触应力在一定范围内随压缩率及槽口半径的 增大而增大。为振动器的结构优化与可靠性设计提供理论依据,并为油气资源勘探开发 的安全作业提供工程应用指导。     

Design and use of group-specific primers and probes for real-time quantitative PCR

Real-time quantitative polymerase chain reaction (qPCR) has gained popularity as a technique to detect and quantify a specific group of target microorganisms from various environmental samples including soil, water, sediments, and sludge. Although qPCR is a very useful technique for nucleic acid quantification, accurately quantifying the target microbial group strongly depends on the quality of the primer and probe used. Many aspects of conducting qPCR assays have become increasingly routine and automated; however, one of the most important aspects, designing and selecting primer and probe sets, is often a somewhat arcane process. In many cases, failed or non-specific amplification can be attributed to improperly designed primer-probe sets. This paper is intended to provide guidelines and general principles for designing group-specific primers and probes for qPCR assays. We demonstrate the effectiveness of these guidelines by reviewing the use of qPCR to study anaerobic processes and biologic nutrient removal processes. qPCR assays using group-specific primers and probes designed with this method, have been used to successfully quantify 16S ribosomal Ribonucleic Acid (16S rRNA) gene copy numbers from target methanogenic and ammonia-oxidizing bacteria in various laboratory- and full-scale biologic processes. Researchers with a good command of primer and probe design can use qPCR as a valuable tool to study biodiversity and to develop more efficient control strategies for biologic processes.     

基于EMD-MFOA-ELM的瓦斯涌出量时变序列预测研究

为准确分析工作面绝对瓦斯涌出量的非平稳特征,实现瓦斯涌出量的准确预测,基于经验模态分解(EMD)、修正的果蝇优化算法(MFOA)和极限学习机(ELM)基本原理,构建瓦斯涌出量的EMD-MFOA-ELM多尺度时变预测模型。通过EMD将瓦斯涌出量时变序列进行深层次分解,获得多尺度本征模态函数(IMF);采用MFOA-ELM对各IMF时变序列建立动态预测模型,等权叠加各预测值,得到模型最终预测结果。以晋煤某矿瓦斯涌出量监测时序样本为例进行研究分析,结果表明:EMD能充分挖掘出监测数据隐含信息,有效降低数据复杂度;该模型预测相对误差为0.024 3%~0.651 0%,平均值仅为0.252 6%,预测精度和泛化能力高于未经EMD分解模型,能很好地适用于非平稳时变序列预测。     

基于APJE-SLIM的海运人因失误概率的确定

安全是海运行业永恒的主题,调查研究表明,人因失误是造成海事的主要原因。为了对海运人因失误进行研究,探讨引起人因失误的行为形成因子(PSF),确定在PSF影响下的人因失误概率。在调查海上避让行为的人因失误和这些失误的行为形成因子的基础上,采用APJE和SLIM相结合的方法对航海人员避让行为中的可靠性进行分析。结果表明,航海人员疲劳与健康程度、知识、经验与培训水平、任务复杂程度、安全管理水平与组织有效性等PSF对人因失误概率有着不同程度的影响,相应提高PSF水平,可极大地减少人因失误概率。利用APJE确定端点绝对失误概率,解决了SLIM方法中难以获得参考点概率的问题,获得了在不同种类不同水平PSF影响下的海运人因失误概率。     

A method to estimate pre-exploitation population size

Antarctic fur seals (Arctocephalus gazella) were commercially exploited on the subantarctic island of South Georgia for over 100 years and nearly driven to extinction. Since the cessation of harvesting, however, their populations have rebounded, and they are now often considered a nuisance species whose impact on the terrestrial landscape should be mitigated. Any evaluation of their current population requires the context provided by their historic, pre-exploitation abundance, lest ecologists fall prey to shifting baseline syndrome in which their perspective on current abundance is compared only with an altered state resulting from past anthropogenic disturbance. Estimating pre-exploitation abundance is critical to defining species recovery and setting recovery targets, both of which are needed for the International Union for the Conservation of Nature's recent efforts to develop a green list of recovering species. To address this issue, we reconstructed the South Georgia fur seal harvest from 1786 to 1908 from ship logbooks and other historical records and interpolated missing harvest data as necessary with a generalized linear model fit to the historical record. Using an approximate Bayesian computation framework, harvest data, and a stochastic age-structured population model, we estimated the pre-exploitation abundance of Antarctic fur seals on South Georgia was 2.5 million females (95% CI 1.5–3.5 million). This estimate is similar to recent abundance estimates, and suggests current populations, and the ecological consequences of so many fur seals on the island, may be similar to conditions prior to human harvest. Although the historic archive on the fur sealing era is unavoidably patchy, the use of archival records is essential for reconstructing the past and, correspondingly, to understanding the present. Article impact statement: Defining species recovery requires an understanding of baseline population state, which can be estimated through statistical methods.     

T型槽密封结构的有限元分析及试验验证

目的通过有限元分析,实现T型密封结构的优化设计。方法利用ABAQUS建立液压系统用T型槽密封结构的二维轴对称模型,分析计算密封结构中过渡圆角、槽宽、倾斜角度等对密封圈应力分布、接触应力的影响,通过设计密封圈老化寿命试验,验证分析结论。结果随着过渡圆角(R0.5～R2)的增大、倾斜角度(10°～3°)的减小,密封圈的局部应力最大值和接触应力均减小。随着槽宽(10～18mm)的增加,密封圈的局部应力最大值逐渐增加,接触应力逐渐减小。分析用密封结构的接触应力均大于密封介质压力0.7 MPa。最终通过试验证实了分析用密封结构均满足密封性能,且不合理的设计会降低密封圈寿命。结论在密封介质压力较小的情况下,建议选用较大的过渡圆角(推荐值为R2),较小的倾斜角度(推荐值为5°～6°)及槽宽(推荐值为密封圈截面直径的1.2～1.5倍)。     

转子-轴承-干气密封系统振动响应及结构优化

目的为了提高干气密封系统在运行工况下的稳定性,对密封螺旋槽槽型参数进行优化。方法根据转子-轴承-干气密封系统轴向振动动力学模型,建立双自由度振动方程。在特定的工况下,通过Maple软件多次拟合求解气膜非线性方程,得到气膜轴向刚度和阻尼。运用MATLAB软件中的龙格-库塔法对三阶的非线性振动方程数值求解,绘制不同螺旋角度下的时间历程图和相图,分析对比不同螺旋角度下静环的振动位移。结果从螺旋角度与静环振动位移的关系得出,当α=74.53°时,静环振动位移最小,其最大振幅为7μm,最大振速为7μm/s;当α=73.78°时,静环振动位移最大,其最大振幅为16.5μm,最大振速为17μm/s。改变螺旋角度可以调节和减小静环的振幅。结论在考虑叶轮转子的气动力和轴承油膜力的干气密封系统下,螺旋角度的增加能够提高系统运行的稳定性,增加螺旋角度(0.5°~0.6°)使得动静环的追随性最佳,对干气密封结构的设计提出了指导。