南海17940孔晚更新世末期以来菱形海线藻及其变种的古环境研究          下载免费PDF全文

沙龙滨  黄玥  王蕾 《气象与环境学报》2008,24(5):6-10

通过对1994年南海17940孔硅藻数据进行分析,结果表明：该孔硅藻组合中菱形海线藻及其变种T. nitzschioides var. parva的百分含量比值具有一定的变化规律。通过比对南海17940孔已有温度记录（有孔虫G. rubberδ18O数据、FP-12E表层海水年平均温度）,进一步发现菱形海线藻变种（T. nitzschioides var. parva）与原种的比值所反应的温度变化与原有记录具有较好的一致性。其中,比值增加反映了古温度的升高;反之则说明气候变冷。因此,该比值可反映出自晚更新世末期以来该地区古温度的变化情况,是较好的古温度指示标志。  相似文献   

Analysis of HST ultraviolet spectra for T Tauri stars: RU Lup     

S. A. Lamzin 《Astronomy Letters》2000,26(4):225-232

The ultraviolet spectra of the star RU Lup obtained with the Hubble Space Telescope are analyzed. Emission lines are identified. The presence of absorption components with a nearly zero residual intensity in the Mg II resonance doublet lines is indicative of mass outflow with a velocity V _∞?300 km s^?1. These lines also exhibit a broad (?1400 km s^?1 at the base) component originating in the star itself. The profiles of the (optically thin) Si II] and Si III]1892 Å lines for the first time unequivocally prove that these lines originate in an accretion shock wave rather than in the chromosphere, with the gas infall velocity being V ₀?400 km s^?1. The intensity ratio of the C IV 1550 Å and Si IV 1400 Å resonance doublet components was found to be close to unity, suggesting a high accreted-gas density, logN ₀>12.5. Molecular H₂ Lyman lines formed in the stellar wind were detected. The H I Lα luminosity of RU Lup was found from their intensities to exceed 10% of L _bol. Radiation pressure in the Lα line on atomic hydrogen may play a significant role in the initial acceleration of stellar-wind matter, but the effect of Lα emission on the dynamics of molecular gas is negligible.  相似文献   

人工诱导雌核发育牙鲆的染色体及核型证明   总被引：6，自引：1，他引：5  

刘静  尤锋  王新成  徐永立  张培军 《海洋与湖沼》1999,30(1):68-72

于1994-1996年,分别在威海海洋渔业捕捞公司（石岛）和鸿洋实业总公司龙须岛育苗场采集人工培育的3－5龄牙鲆亲鱼,采用紫外线照射法使牙鲆精子遗传物质失活,并用冷休克法抑制受精卵第二极体释放,从而获得雌核发育二倍体牙好。原肠期采用空气干燥法、Giemsa染色,得到雌核发育二倍体、正常二倍体及单倍体的染色体制片,进行染色体和核型的分析。结果表明,牙鲆的雌核发育二倍体和正常二倍体的染色体数均为2n=48,核型为48t,即48条端部着色点染色体,臂数NF=48,两者的核型设有明显差异;单倍体为24条端部着丝点染色体;在3个组别中,第一号染色体上都有一明显的次缢痕。雌核发育二倍体牙鲆的诱导率为98％。  相似文献   

环境因子对牙鲆精子运动能力的影响   总被引：8，自引：1，他引：7  

王宏田  张培军 《海洋与湖沼》1999,30(3):233-237

于1997年5-6月,在山东荣成市石岛养殖场采用挤压法收集牙鲆亲鱼的精子,利用显微镜观察精子的活力,研究外界环境因子的变化对牙鲆精子运动能力的影响。结果表明,将蔗糖、NaCl、KCl、MgCl2、CaCl2等溶解于去离子水中,制成不同浓度即具有不同渗透压的溶液,不同渗透压的溶液对精子运动的诱导结果不同。EDTANa2溶液不能诱导精子运动。在人工海水中加入一定量的EDTANa2后,可使原先运动的精子静止;在该溶液中加入新的Ca2 后,将不再诱导原来受到EDTANa2抑制的精子。如用MgSO4代替溶液中的CaCl2,可诱导精子运动;而当用MgCl2代替溶液中的CaCl2,以及用CaCl2或NaCl代替MgSO4时,溶液即失去诱导精子运动的能力。在pH＝4.0-9、5的海水中,牙解精子均可正常运动。  相似文献   

Polarization models of young stellar objects – II. Linear and circular polarimetry of R Coronae Australis     

Stuart Clark  Alan McCall  Antonio Chrysostomou  Tim Gledhill  Jeremy Yates  James Hough 《Monthly notices of the Royal Astronomical Society》2000,319(2):337-349

Near-infrared linear imaging polarimetry of the young stellar objects R CrA and T CrA in the J , H and K n bands, and circular imaging polarimetry in the H band, is presented. The data are modelled with the Clark and McCall scattering model. The R CrA and T CrA system is shown to be a particularly complex scattering environment. In the case of R CrA there is evidence that the wavelength dependence of polarization changes across the nebula. MRN dust grain models do not explain this behaviour. Depolarization by line emission is considered as an alternative explanation. The dust grain properties could also be changing across the nebula.
Although surrounded by reflection nebulosity, there is a region of particularly low polarization surrounding R CrA that is best modelled by the canonical bipolar outflow being truncated by an evacuated spherical cavity surrounding the star. The symmetry axis of the nebula appears inclined by 50° to the plane of the sky.
The H -band circular polarimetry of R CrA clearly shows a quadrupolar structure of positive and negative degrees of circular polarization that reach peak magnitudes of ∼5 per cent within our limited map. It is shown that spherical MRN grains are incapable of producing this circular polarization given the observed linear polarization of the R CrA system. Instead, scattering from aligned non-spherical grains is proposed as the operating mechanism.
T CrA is a more archetypical bipolar reflection nebula, and this object is modelled as a canonical parabolic reflection nebula that lies in the plane of the sky. The wavelength independence of linear polarization in the T CrA reflection nebula suggests that the scattering particles are Rayleigh sized. This is modelled with the MRN interstellar grain size distribution.  相似文献   

Simultaneous horst-basin formation and magmatism during Late Variscan transtension: evidence from 40Ar/39Ar and 207Pb/206Pb geochronology in the Ruhla Crystalline Complex     

A. Zeh  M. A. Cosca  H. Brätz  M. Okrusch  M. Tichomirowa 《International Journal of Earth Sciences》2000,89(1):52-71

40 Ar/³⁹Ar–mica and ²⁰⁷Pb/²⁰⁶Pb–zircon dates are presented and combined with existing P–T data and the sedimentary record. These data indicate that the RCC was faulted into three segments which underwent different exhumation histories during the Late Carboniferous/Early Permian. The eastern segment shows ⁴⁰Ar/³⁹Ar–biotite data of336 ±4 and 323±3 Ma. Furthermore, it is intruded by the Thuringian Hauptgranite dated at 337±4 Ma by the ²⁰⁷Pb/²⁰⁶Pb single zircon method. At approximately 300 Ma rocks of the eastern segment were finally exposed and, subsequently, subsided as part of the Oberhof pull-apart basin, filled by Late Carboniferous/Early Permian molasse sediments and volcanic rocks (296–285 Ma; Goll 1996). A similar Late Carboniferous evolution is inferred for the western segment, since it is also overlain by Upper Carboniferous volcanic rocks. In contrast to the eastern and western segments, distinctly younger intrusion and cooling ages were recorded for the central segment of the RCC (⁴⁰Ar/³⁹Ar muscovite: 311±3 Ma; ⁴⁰Ar/³⁹Ar biotite: 293–288±3 Ma) that was intruded by the Trusetal Granite, the Ruhla Granite and Brotterode Diorite (²⁰⁷Pb/²⁰⁶Pb single zircon: 298±2, 295±3, 289±4 Ma, respectively). These young data are unique in the MGCR and testify that plutonic activity and cooling of basement rocks took place simultaneously with basin formation and volcanism in the eastern and western segments. Overlying Upper Permian (Zechstein) and Triassic sediments indicate final exposure of the central segment by approximately 260 Ma, as a part of the Ruhla-Schleusingen Horst. Combination of these results with P–T data from the contact aureole of the Trusetal granite indicate that the central segment was unroofed by at least 8.5 km during the Late Carboniferous. The Late Carboniferous/Early Permian horst-basin formation, documented in the RCC, is due to dextral transtensional movements along the NW-trending Franconian fault system. It may have been enhanced by mantle upwelling widespread in Central Europe during the Early Permian that also caused intensive magmatism in the Thuringian Forest region. Received: 2 February 1999 / Accepted: 15 November 1999  相似文献   

岩石物理岩石孔喉结构特征对核磁T2谱影响的数值模拟   总被引：2，自引：2，他引：0  

王克文  李宁 《应用地球物理》2008,5(2):86-91

We built a three-dimensional irregular network model which can adequately describe reservoir rock pore-throat structures. We carried out numerical simulations to study the NMR T2 distribution of water-saturated rocks. The results indicate that there is a good correlation between T2 distribution and the pore radius frequency histogram. The total T2 distribution can be partitioned into pore body and pore throat parts. The effect of parameters including throat radius, pore-throat ratio, and coordination number of the micro- pore structure on the T2 distribution can be evaluated individually. The result indicates that： 1 ） with the increase of the pore throat radius, the T2 distribution moves toward longer relaxation times and its peak intensity increases; 2） with the increase of the pore-throat ratio, the T2 distribution moves towards longer T2 with the peak intensity increasing and the overlap between pore body T2 and pore throat T2 decreasing; 3） With the increase of connectivity, the short T2 component increases and peak signal intensity decreases slightly.  相似文献   

基于岩石物理转换模型的苏里格致密砂岩储层测井评价与产能预测          下载免费PDF全文

潘保芝  房春慧  郭宇航  张丽华  雷健  范雨霏 《地球物理学报》2018,61(12):5115-5124

苏里格地区致密砂岩储层勘探开发难度很大,测井解释遇到了储层参数计算和产能预测不准确的问题.本文针对这些难点,基于已有的转换模型,推导并验证了T₂-I和T₂-K_r转换模型,提出了采用转换模型应用于测井综合解释和产能预测的方法.基于实验数据设定孔径大于1 μm的孔隙为大孔,中孔孔径在1 μm和0.03 μm之间,小孔孔径为0.03 μm以下.并建立了不同孔径范围模型中关键参数α与核磁参数T_2lm的关系,这为转换模型在测井解释中的应用提供了必要条件.本文在苏里格西区分别应用T₂-I和T₂-K_r转换模型求取含水饱和度和相对渗透率曲线,并进行产能预测,处理结果显示该方法具有很好的应用效果.  相似文献   

Metamorphic olivine after dehydration embrittlement in Serpentinite: Case study from the Shiraga Serpentinite mass in the Sanbagawa high P/T metamorphic belt,central Shikoku,Japan     

Seiya Fukumura  Kazuaki Okamoto  Masaru Terabayashi 《Island Arc》2019,28(2)

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Stability of LRS Bianchi type-I cosmological models in f(R,T)-gravity     

Umesh Kumar Sharma  Rashid Zia  Anirudh Pradhan  Aroon Beesham 《天文和天体物理学研究(英文版)》2019,(4):63-76

This paper examines the stability of the transition from the early decelerating stage of the Universe to the recent accelerating stage for the perfect fluid cosmological locally rotationally symmetric(LRS) Bianchi-I model in f(R, T) theory. To determine the solution of field equations, the idea of a timevarying deceleration parameter(DP) which yields a scale factor, for which the Universe attains a phase transition scenario and is consistent with recent cosmological observations, is used. The time-dependent DP yields a scale factor a=exp■, where β and k are respectively arbitrary and integration constants. By using the recent cons_traints(H_0 _= 73.8, and q_0 =-0.54) from Type Ia Supernova(SN Ia) data in combination with Baryonic Acoustic Oscillations(BAO) and Cosmic Microwave Background(CMB) observations(Giostri et al.), we obtain the values of β = 0.0062 and k = 0.000016 for which we have derived a cosmological model from the early decelerated phase to the present accelerating phase. By applying_ other r_ecent constraints(H_0 = 73.8, q_0 =-0.73) from SNe Ia Union data(Cunha), we obtain the values of β = 0.0036 and k = 0.000084 for which we have derived a cosmological model in the accelerating phase only. We have compared both models with experimental data. The stability of the background solution has been examined also for the metric perturbations alongside the properties of future singularities in a Universe ruled by dark energy with phantom type fluid. We demonstrate the presence of a stable fixed point with a condition of state ω <-1 and numerically affirm this is really a late-time attractor in the ghost overwhelmed Universe. Some physical and geometric properties of the model are found and examined.  相似文献