分类: 生物学 >> 动物学 提交时间: 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要: Four types of footprints of carnivorous dinosaurs have been found from the Yan’an Formation of early Middle Jurassic in Zizhou County, Shaanxi, China. From the top to bottom interval, the four types of footprints discovered at five layers in a 1.7 m thick stratum are as follows: 1) the large tridactyl footprints in the fifth layer (e, top) belong to Zizhoupus wangi ichnogen. et ichnosp. nov.; 2) the medium tridactyl footprints in the third and fourth layers (c–d) belong to Changpeipus longweimaoensis ichnosp. nov.; 3) small tridactyl or tetradactyl footprints in the second layer (b) belong to Shensipus xiaoliheensis ichnosp. nov. and 4) small tridactyl footprints in the first layer (a, bottom) belong to Shensipus tungchuanensis.
分类: 地球科学 >> 地质学 提交时间: 2017-08-08 合作期刊: 《古脊椎动物学报》
摘要: Four types of footprints of carnivorous dinosaurs have been found from the Yan’an Formation of early Middle Jurassic in Zizhou County, Shaanxi, China. From the top to bottom interval, the four types of footprints discovered at five layers in a 1.7 m thick stratum are as follows: 1) the large tridactyl footprints in the fifth layer (e, top) belong to Zizhoupus wangi ichnogen. et ichnosp. nov.; 2) the medium tridactyl footprints in the third and fourth layers (c–d) belong to Changpeipus longweimaoensis ichnosp. nov.; 3) small tridactyl or tetradactyl footprints in the second layer (b) belong to Shensipus xiaoliheensis ichnosp. nov. and 4) small tridactyl footprints in the frst layer (a, bottom) belong to Shensipus tungchuanensis.
分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: The existing 210Pbex mass balance models for the assessment of cultivated soil erosion are based on an assumption that 210Pbex is quite evenly mixed within the plough layer. However, the amount of 210Pbex distributed in the soils below the plough depth, like a downward tail in the lower part of the 210Pbex profile, has been largely ignored. In fact, after the initial cultivation of undisturbed soils, 210Pbex will diffuse downward from plough layer to the plough pan layer due to the concentration gradient. Assuming 210Pbex inventory is constant, the depth distribution in the two layers of the cultivated soils will achieve a steady state after continuous cultivation for 10.37 years, when 210Pbex is evenly distributed in the soils of the plough layer with an exponential concentration decline with depth in the soils of the plough pan layer, and the 210Pbex concentration at any depth will be invariable with time. The work reported in this paper attempts to explain the formation of the 210Pbex tail in the soil profile below the plough depth by theoretical derivation of the 210Pbex depth distribution process in the two layers of the cultivated soils, propose a 210Pbex mass balance model considering 210Pbex diffusion based on the existing model, and discuss the influence of the 210Pbex tail to the existing model.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-05-09
摘要: Using the non-relativistic hydrodynamic limit, we solve equations of motion for Einstein gravity and Gauss-Bonnet gravity with a negative cosmological constant within the region between a finite cutoff surface and a black brane horizon, up to second order of the non-relativistic hydrodynamic expansion parameter. Through the Brown-York tensor, we calculate the stress energy tensor of dual fluids living on the cutoff surface. With the black brane solutions, we show that for both Einstein gravity and Gauss-Bonnet gravity, the ratio of shear viscosity to entropy density of dual fluid does not run with the cutoff surface. The incompressible Navier-Stokes equations are also obtained in both cases.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-05-09
摘要: Recently Lysov and Strominger [arXiv:1104.5502] showed that imposing Petrov type I condition on a (p+1)-dimensional time like hypersurface embedded in a (p+2)-dimensional vacuum Einstein gravity reduces the degrees of freedom in the extrinsic curvature of the hypersurface to that of a fluid on the hypersurface, and that the leading-order Einstein constraint equations in terms of the mean curvature of the embedding give the in compressible Navier-Stokes equations of the dual fluid. In this paper we show that the non-relativistic fluid dual to vacuum Einstein gravity does not satisfy the Petrov type I condition at next order, unless additional constraint such as their rotational condition is added. In addition, we show that this procedure can be inversed to derive the non-relativistic hydrodynamics with higher order corrections through imposing the Petrov type I condition, and that some second order transport coefficients can be extracted, but the dual "Petrov type I fluid" does not match the dual fluid constructed from the geometry of vacuum Einstein gravity in the non-relativistic limit. We discuss the procedure both on the finite cut off surface via the non-relativistic hydrodynamic expansion and on the highly accelerated surface via the near horizon expansion.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-05-09
摘要: We investigate the behaviors of entanglement entropy in the holographical insulator/superconductor phase transition. We calculate the holographic entanglement entropy for two kinds of geometry configurations in a completely back-reacted gravitational background describing the insulator/superconductor phase transition. The non-monotonic behavior of the entanglement entropy is found in tins system. In the belt geometry case, there exist four phases characterized by the chemical potential and belt width.
分类: 生物学 >> 动物学 提交时间: 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要: Sabertooth cats were extinct carnivorans that have attracted great attention and controversy because of their unique dental morphology representing an entirely extinct mode of feeding specialization. Some of them are lion-sized or tiger-sized carnivorans who are widely interpreted as hunters of larger and more powerful preys than those of their modern nonsaber-toothed relatives. We report the discovery of a large sabertooth cat skull of Machairodus horribilis from the Late Miocene of northwestern China. It shares some characteristics with derived sabertooth cats, but also is similar to extant pantherines in some cranial characters. A functional morphological analysis suggests that it differed from most other machairodont felids and had a limited gape to hunt smaller preys. Its anatomical features provide new evidence for the diversity of killing bites even within in the largest saber-toothed carnivorans and offer an additional mechanism for the mosaic evolution leading to functional and morphological diversity in sabertooth cats.
分类: 地球科学 >> 地质学 提交时间: 2017-08-11 合作期刊: 《古脊椎动物学报》
摘要: Sabertooth cats were extinct carnivorans that have attracted great attention and controversy because of their unique dental morphology representing an entirely extinct mode of feeding specialization. Some of them are lion-sized or tiger-sized carnivorans who are widely interpreted as hunters of larger and more powerful preys than those of their modern nonsaber-toothed relatives. We report the discovery of a large sabertooth cat skull of Machairodus horribilis from the Late Miocene of northwestern China. It shares some characteristics with derived sabertooth cats, but also is similar to extant pantherines in some cranial characters. A functional morphological analysis suggests that it differed from most other machairodont felids and had a limited gape to hunt smaller preys. Its anatomical features provide new evidence for the diversity of killing bites even within in the largest saber-toothed carnivorans and offer an additional mechanism for the mosaic evolution leading to functional and morphological diversity in sabertooth cats. 剑齿虎是一类绝灭的食肉目动物,由于其独特的牙齿形态代表了已完全消失的特化取食方式而引起了极大的关注和争论。一些剑齿虎是狮子体型或老虎体型的食肉动物,它们被广泛认为能够比其不具剑形犬齿的现代近亲捕杀更大和更强壮的猎物。本文报道在甘肃省晚中新世地层中发现的一具属于恐剑齿虎(Machairodus horribilis)的大型头骨。这件标本的一些特征与进步的剑齿虎相同,但在某些头骨性状上则与现生的豹亚科种类相似。不同于其他大多数剑齿虎,功能形态分析指示该剑齿虎的口部张开程度受到限制,因此只能捕猎相对较小的猎物。这具头骨的解剖特征为证明即使在最大的具剑形犬齿的食肉目动物中也存在捕猎咬杀方式的多样性提供了新的证据,并揭示了在剑齿虎中导致功能和形态多样性镶嵌进化的另一种机制。
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-05-09
摘要: We study the thermodynamics and non-relativistic hydrodynamics of the holographic fluid on a finite cutoff surface in the Gauss-Bonnet gravity. It is shown that the isentropic flow of the fluid is equivalent to a radial component of gravitational field equations. We use the non-relativistic fluid expansion method to study the Einstein-Maxwell-dilaton system with a negative cosmological constant, and obtain the holographic incompressible forced Navier-Stokes equations of the dual fluid at AdS boundary and at a finite cutoff surface, respectively. The concrete forms of external forces are given. (c) 2012 Elsevier B.V. All rights reserved.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-05-09
摘要: We investigate the scalar perturbations in an anti-de Sitter soliton background coupled to a Maxwell field via marginally stable modes. In the probe limit, we study the magnetic field effect on the holographic insulator/superconductor phase transition numerically and analytically. The condensate will be localized in a finite circular region for any finite constant magnetic field. Near the critical point, we find that there exists a simple relation among the critical chemical potential, magnetic field, the charge, and mass of the scalar field. This relation indicates that the presence of the magnetic field causes the transition from insulator to superconductor to be difficult.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: TiO2 nanofilms on surface of fused silica were fabricated by Ti ion implantation and subsequent thermal annealing in oxygen ambience. The silica glasses were implanted by 20 kV Ti ions to 1.5�1017 ions/cm2 on an implanter of metal vapor vacuum arc (MEVVA) ion source. Effects of annealing parameters on formation, growth and phase transformation of the TiO2 nanofilms were studied in detail. Optical absorption spectroscopy, Raman scattering spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy measurements were done to figure out formation mechanism of the TiO2 nanofilms. The formation of TiO2 nanofilms was due to out-diffusion of the implanted Ti ions to the substrate surface, where they were oxidized into TiO2 nanoparticles. Formation, phase, and thickness of the TiO2 nanofilms can be well tailored by controlling annealing parameters.
分类: 生物学 >> 动物学 提交时间: 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要: This paper describes some micromammal fossils which were excavated from the South Longyadong Cave in the Luonan Basin, eastern Qinling Mountains of Shaanxi Province, central China. The fauna include 15 mammals consisting by Scapanulus oweni, Nasillus andersoni, Uropsilinae gen. et sp. indet., Soriculus sp., Ochotona cf. O. alpina, Belomys parapearsoni, Allocricetus ehiki, Proedromys bedfordi, Allophaiomys deucalion, Eospalax sp., Niviventer preconfucianus, Apodemus asianicus, Apodemus sp., Hystrix brachyura subcristata, Trogontherium cuvieri. Among them, Nasillus andersoni and Ochotona cf. O. alpina are the newly discovered fossil species. The fossil assemblage characteristics of newly micromammal faunal is similar to the North Longyadong Cave Fauna, and the geological age should not be later than early Middle Pleistocene. It might be a fauna of late Early Pleistocene. But in recent years, the thermoluminescence age of fossiliferous strata corresponding are 356.6�7.8 ka BP, 273.9�3.7 ka BP and 210.5�0.5 ka BP. The fauna is including both the south and the north animals, the animal combination obviously has the characteristics of the transition between the south and the north of China.
分类: 地球科学 >> 地质学 提交时间: 2017-08-11 合作期刊: 《古脊椎动物学报》
摘要: This paper describes some micromammal fossils which were excavated from the South Longyadong Cave in the Luonan Basin, eastern Qinling Mountains of Shaanxi Province, central China. The fauna include 15 mammals consisting by Scapanulus oweni, Nasillus andersoni, Uropsilinae gen. et sp. indet., Soriculus sp., Ochotona cf. O. alpina, Belomys parapearsoni, Allocricetus ehiki, Proedromys bedfordi, Allophaiomys deucalion, Eospalax sp., Niviventer preconfucianus, Apodemus asianicus, Apodemus sp., Hystrix brachyura subcristata, Trogontherium cuvieri. Among them, the Nasillus andersoni and the Ochotona cf. O. alpina are the newly discovered fossil species. The fossil assemblage characteristics of newly micromammal faunal is similar to the North Longyadong Cave Fauna, and the geological age should not be later than early Middle Pleistocene. It might be a fauna of late Early Pleistocene. But in recent years, the thermoluminescence age of fossiliferous strata corresponding are 356.6±17.8 kaBP, 273.9±13.7 kaBP and 210.5±10.5 kaBP. The fauna is including both the south and the north animals, the animal combination obviously has the characteristics of the transition between the south and the north of China. 描述了1995~1997年东秦岭山地洛南盆地龙牙南洞洞穴遗址中发掘出土的小哺乳动物化石,包括甘肃鼹Scapanulus oweni, 峨眉鼩鼹Nasillus andersoni, 鼩鼹(属种未定) Uropsilinae gen. et sp. indet., 长尾鼩鼱Soriculus sp., 似高山鼠兔Ochotona cf. O. alpina, 偏皮氏毛耳飞鼠Belomys parapearsoni, 艾克氏异仓鼠Allocricetus ehiki, 沟牙田鼠Proedromys bedfordi, 欧洲异费鼠Allophaiomys deucalion, 始鼢鼠Eospalax sp., 先社鼠Niviventer preconfucianus, 亚洲姬鼠Apodemus asianicus, 姬鼠Apodemus sp., 马来豪猪(华南亚种) Hystrix brachyura subcristata, 居氏大河狸Trogontherium cuvieri等。该动物群同时包括南方型和北方型动物,其动物组合具有明显的南北过渡地带的特征。其中峨眉鼩鼹和似高山鼠兔为新发现的化石种。新发现的小哺乳动物化石组合类似于龙牙北洞,显示出比较古老的性质,时代上多为早更新世晚期或中更新世早期,但龙牙南洞遗址含化石地层对应的热释光(TL)年龄结果分别为(356.6±7.8) kaBP, (273.9±3.7) kaBP和(210.5±0.5) kaBP, 最近新的回授光释光(TT-OSL)测年数据进一步验证了热释光测年结果,获得的地层年代亦为距今40~20万年左右。
分类: 地球科学 >> 地质学 提交时间: 2017-09-28 合作期刊: 《古脊椎动物学报》
摘要: 描述了在兰州盆地渐新统韩家井组底部的黄砂层中新发现的巨犀化石:黄河巨犀(Paraceratherium huangheense sp. nov.) (新种), 该化石产出层位的古地磁年龄为距今31.5Ma。新种主要特征为:P2之前无齿槽痕迹,一对下门齿粗壮,互相靠近,向前平伸且略微上翘,下颏孔位于p3之下,水平支下缘平直, p2前的齿隙部分向上隆起,下颌角圆钝,上升支后缘斜向后上方,齿式: ?·?·3·3/1·0·3·3。除个体较大、下颌后缘有所不同之外,其下颌的总体特征与巴基斯坦的Paraceratherium bugtiense最为接近,显示两者可能具有较近的亲缘关系。新标本的发现为确定经典的Dera Bugti地点产大巨犀化石层位的年代提供了新的证据,并为青藏高原的隆升讨论提供了新的哺乳动物化石证据。
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-05-09
摘要: We study the Wilson line response in the holographic superconducting phase transitions in the Gauss-Bonnet gravity. In the black brane background case, the Little-Parks periodicity is independent of the Gauss-Bonnet parameter, while in the anti-de Sitter soliton case, there is no evidence for the Little-Parks periodicity. We further study the impact of the Gauss-Bonnet term on the holographic phase transitions quantitatively. For a given Wilson line, a bigger Gauss-Bonnet coefficient makes the phase transition easier for the black brane background while harder for the soliton background. For a given chemical potential, the response to the Wilson line is less sensitive for a bigger Gauss-Bonnet coefficient in the black brane case while the response is more sensitive in the soliton case. And more, a bigger Gauss-Bonnet coefficient makes the superconducting state more stable for both the black brane and the soliton backgrounds. DOI: 10.1103/PhysRevD.87.026002
分类: 生物学 >> 生物物理学 提交时间: 2016-05-11
摘要: Developing chimeric lysins with a wide lytic spectrum would be important for treating some infections caused by multiple pathogenic bacteria. In the present work, a novel chimeric lysin (Ply187N-V12C) was constructed by fusing the catalytic domain (Ply187N) of the bacteriophage lysin Ply187 with the cell binding domain (146-314aa, V12C) of the lysin PlyV12. The results showed that the chimeric lysin Ply187N-V12C had not only lytic activity similar to Ply187N against staphylococcal strains but also extended its lytic activity to streptococci and enterococci, such as Streptococcusdysgalactiae, Streptococcus agalactiae, Streptococcus pyogenes, Enterococcus faecium and Enterococcus faecalis, which Ply187N could not lyse. Our work demonstrated that generating novel chimeric lysins with an extended lytic spectrum was feasible through fusing a catalytic domain with a cell-binding domain from lysins with lytic spectra across multiple genera.
分类: 天文学 >> 天文学 提交时间: 2024-05-24 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: Owing to the broad energy coverage of Insight-HXMT in the hard X-ray band, we detected the highest energy of pulsation exceeding 200 keV around the 2017–2018 outburst peak of the first Galactic pulsating ultraluminous X-ray source (PULX) Swift J0243.6+6124, which is the highest energy detected from PULXs to date. We also obtained the highest energy of pulsation of every exposure during the outburst in 2017–2018, and found the highest energy is roughly positively correlated with luminosity. Using our newly developed method, we identified the critical luminosity being 4 × 1038 erg s−1 when the main peaks of the low and high energy pulse profiles became aligned, which separates the fan-beam dominated and pencil-beam dominated accretion regimes. Above the critical luminosity, the phase of the main peak shifted gradually from 0.5 to 0.8 until the outburst peak in all energy bands is reached, which is in agreement with the phase shift found previously at low energies. Our result is consistent with what is derived from spectral analysis.
分类: 核科学技术 >> 粒子加速器 提交时间: 2021-12-31
摘要: Collinear laser spectroscopy is a powerful tool for studying the nuclear spins, electromagnetic moments, and charge radii of exotic nuclei. To study the nuclear properties of unstable nuclei at the Beijing Radioactive Ion#2;beam Facility (BRIF) and the future High Intensity Heavy-ion Accelerator Facility (HIAF), we developed a collinear laser spectroscopy apparatus integrated with an offline laser ablation ion source and a laser system. The overall performance of this state-of-the-art technique was evaluated and the system was commissioned using a bunched stable ion beam. The high-resolution optical spectra for the 4s 2S1/2 → 4p 2P3/2 (D2) ionic transition of 40,42,44,48Ca isotopes were successfully measured. The extracted isotope shifts relative to 40Ca showed excellent agreement with the literature values. This system is now ready for use at radioactive ion beam facilities such as the BRIF and paves the way for the further development of higher-sensitivity collinear resonant ionization spectroscopy techniques.