一个非线性连续培养模型极限环的位置

微生物培养是生化工程中的一个重要课题。研究了一个非线性连续微生物培养动力系统的极限环的相对位置。对带非常数产物系数的连续培养模型进行推广。模型中的极限环对应于发酵和生化培养中的非线性振荡,其相对位置对研究连续培养中振荡产生的时间和范围是有意义的。     

A 640 kyr geomagnetic and palaeoclimatic record from Lake Baikal sediments

Magnetic remanence vectors for 1737 samples from two ∼100 m cores of Lake Baikal sediments are reported along with complete magnetic susceptibility profiles obtained from a pass-through system. Chronological control is established by means of two independent correlations; first, by matching susceptibility variations to the oceanic oxygen isotope record and second, by matching the relative palaeointensity variations to the SINT-800 global reference curve. These both imply an average deposition rate of 15 cm kyr^–1 and a basal age of ∼640 ka. Spectral analysis reveals the presence of Milankovitch signals at ∼100 kyr (eccentricity), ∼41 kyr (obliquity) and ∼23 and ∼19 kyr (precession). Stable remanence vectors are almost all of normal polarity. The few exceptions comprise brief intervals of low and/or negative inclinations which probably represent geomagnetic excursions. However, these are far less numerous than the high sedimentation rate would lead one to expect. Furthermore, only four of them can be readily matched to the—still poorly understood—global pattern. These are the Laschamp, the Albuquerque, the Iceland Basin and perhaps the West Eifel excursions which occurred at ∼38 000, ∼146 000, at 180 000–190 000 and at 480 000–495 000 yr ago, respectively.     

Carbon and oxygen isotopic variations in peritidal stromatolite cycles, Paleoproterozoic Kajrahat Limestone, Vindhyan basin of central India

Variations of carbon and oxygen isotopic ratios in response to cyclical sea level fluctuations have been documented from a Paleoproterozoic peritidal stromatolite succession. The upper division of the Kajrahat Limestone, Vindhyan Supergroup of central India consists of several shallowing upward stromatolite cycles identified by regular and systematic changes in stromatolite size. Normally, larger stromatolites are followed upward in the succession by smaller stromatolites and microbial laminites that occupy the top of the cycle. Desiccation cracks are found in all the facies indicating subaerial exposure. We investigated the stable isotope compositional variations across nine complete stromatolite cycles showing frequent subaerial emergence. Carbon and oxygen isotopic values of the limestones, in general, are comparable to contemporary marine values available from earlier studies but show regular depletion in response to shallowing of the water level. The δ¹³C and δ¹⁸O values of the limestones vary within an individual stromatolite cycle; depleted values characterize the topmost part of the cycles. The isotope pattern is explained by micritic carbonate deposition in different sub environments of the shallow marine domain having different salinity and variable duration of exposure. These variations also probably caused the observed scatter in δ¹³C and δ¹⁸O values of supratidal microbial laminites.     

Triassic Sequence Stratigraphy and Sea-Level Changes in Qomolongma Area, Southern Tibet,China: From Epicontinental Sea to Rift Basin

INTRODUCTIONThe Qomolongm a area was paleogeographically situatedon the northern margin of the Indian plate and was part of theGondwana continent in the Mesozoic.In the latest MiddlePermian(late Capitanian) due to the formation of the Pangeasupercontinent,the area was uplifted significantly,resultingin an overall regression and an eminentdisconformity atca2 5 8Ma.During mosttim e of the L ate Perm ian,the Qomolongm aarea was subject to erosion and free of deposit (Shi et al.,1996 ;L …     

Periodic variation of the north-south asymmetry of solar activity phenomena

We report here a study of various solar activity phenomena occurring in both north and south hemispheres of the Sun during solar cycles 8–23. In the study we have used sunspot data for the period 1832–1976, flare index data for the period 1936-1993, Hα flare data 1993–1998 and solar active prominences data for the period 1957–1998. Earlier Verma reported long-term cyclic period in N-S asymmetry and also that the N-S asymmetry of solar activity phenomena during solar cycles 21, 22, 23 and 24 will be south dominated and the N-S asymmetry will shift to north hemisphere in solar cycle 25. The present study shows that the N-S asymmetry during solar cycles 22 and 23 are southern dominated as suggested by Verma.     

Recent increase of DIC in the western North Pacific

The temporal variation of the total dissolved inorganic carbon (DIC) content in the western North Pacific is investigated by comparing the DIC distribution obtained from the data sets of three different periods, the GEOSECS data observed in 1973, the CO₂ dynamics Cruise data observed in 1982, and recent Japanese data sets observed during the early 1990s. The overall feature of the signal of temporal DIC change during 1973 and early 1990s agreed with that of former studies, and did not significantly change with the calculation scheme (the grid-selection method vs. the multiple regression method). The observed increase in DIC among the different time scales showed a good inner consistency, which also indicates the stability of the method used in the DIC change calculation. The apparent rate of increase of the DIC inventory in the upper 1000 m water column, however, differed significantly by the data set used for the calculation: It was 5.6±2.4 g C/m²/year, based on the data comparison between 1982 and the early 1990s, while it became 7.6±2.4 g C/m²/year when based on the data between 1973 and the early 1990s. This result provides us an information about the data-dependency on the former estimation of temporal DIC change.     

辽西金-羊盆地土城子组层序地层学

辽西金-羊（金岭寺-羊山）盆地土城子组为一套红色陆相碎屑岩组合.据其岩层垂向叠置规律及不整合面特征,可划分出3个Ⅲ级旋回层序,14个Ⅳ级旋回层序及各旋回层序所对应的冲积扇、滨湖、浅湖、最大湖泛面、风成沙漠沉积体系.这些沉积体系的有规律叠置,构成了土城子期3次湖扩张-湖萎缩沉积序列,其顶、底为明显的不整合面所界定.通过对旋回层序的划分和对比,建立了辽西金-羊盆地土城子组层序地层格架,从而揭示了中生代侏罗纪上统土城子组沉积期的盆地演化规律.     

认识偏心率周期的地层古气候意义

介绍了偏心率周期在地层和古气候研究方面的新发展.现有地球轨道模式对250Ma以来的轨道运算误差能控制在0.2%之内, 使基于偏心率周期来划分地层年代成为可能.新的国际标准地层年代表以405ka长偏心率周期为基础来划分主要地层界线.新生代将包括E1-E162偏心率长周期, 底界年龄(65.5±0.3) Ma.这一地层年代表的建立, 标志着轨道地层学时代的到来.偏心率的100ka短周期和405ka长周期在诸多地质记录中都有反映, 特别是来自深海钻孔的物理化学古气候指标.很多古气候重大事件往往发生在偏心率周期的弱振幅时期, 表明弱振幅时期易受其他因素的干扰影响, 这些因素包括碳储库、冰盖和海平面变化、电磁场, 以及区域构造重组等等.越来越多的研究发现碳同位素在偏心率周期上与地球轨道驱动相关, 且常领先于氧同位素的变化, 表明热带碳循环过程是影响全球气候变化的关键因素之一.      

Hydrograph separation to improve understanding of Dissolved Organic Carbon Dynamics in Headwater catchments

Dissolved organic carbon (DOC) is a key component of the global carbon cycle, but, to date, large uncertainties still exist on its source and fate in first‐order streams. In a 23 ha rangeland and steep‐slope headwater of South Africa, our aim was to quantify the contribution of overland flow (OF), soil water (SW) and ground water (GW) to DOC fluxes (DOC_F), and to interpret the results in terms of DOC sources and fate. The average 2010–2011 DOC concentration (DOC_C) at the catchment outlet was 4.7 mg C l^?1 with a standard error of ±2.5 mg C l^?1, which was significantly lower than in SW (15.2 ± 1.6 mg C l^?1) and OF (11.9 ± 0.8 mg C l^?1), but higher than in GW (2.3 ± 0.6 mg C l^?1). Based on end‐member mixing using Si and Na concentration in the water compartments, the average SW contribution to DOC_F was 66.4%, followed by OF (30.0%) and GW (3.6%). The resulting estimated DOC_F at the catchment outlet was 8.05 g C m² y^?1. This was much higher than the observed value of 2.80 g C m² y^?1, meaning that 5.25 g C m² y^?1 or 65% of the DOC is lost during its downslope and/or downstream transport to the catchment outlet. Complementary investigations revealed that the DOC_C in SW dropped from 15.2 ± 1.6 to 2.6 ± 0.3 mg C l^?1 during its downslope transport to the river system, which corresponded to a net loss of 5.10 g C m² y^?1, or 97% of the catchment DOC losses. These results on DOC sources and potential fate in headwaters are expected to improve our understanding of the impact of hydrology on the global C‐cycle. Copyright © 2013 John Wiley & Sons, Ltd.