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: The mammalian fossils (Mimolagus and Anagalopsis) from Shanmacheng in the Jiuxi Basin described by Bohlin in 1951 have long been enigmatic in systematics and controversial in the geological age. New survey in this area suggests the fossils were discovered from the Shanmacheng member of the Huoshaogou Formation. Comparisons of the Shanmacheng fossils with new specimens of Mimolagus from the Irdin Mahan Formation, and Anagale from the Late Eocene Ulan Gochu Formation, Nei Mongol, suggest an Eocene age for the Shanmacheng fossils. Reinterpretation of the fossil horizon and the paleomagnetic data of Dai et al. (2005) indicates the polarity zones from Huoshaogou section can be correlated to GPTS Chrons 13−18. Therefore, the Huoshaogou Formation may cover late Middle Eocene to Late Eocene and Bohlin’s fossil horizon can roughly be correlated to Chron18n (~39−40 Ma) of late Middle Eocene. The late Middle Eocene age of Mimolagus rodens narrows the time gap with its close relative Gomphos that have been recorded from Early to Middle Eocene. The archaic group Anagalidae may have become extinct before Oligocene.
分类: 医学、药学 >> 基础医学 提交时间: 2018-06-15 合作期刊: 《南方医科大学学报》
摘要: Rosai-Dorfman病是一种发生在淋巴结或结外组织的良性组织细胞增生性病变,而发生在喉部的结外Rosai-Dorfman病例及其罕见,其病变特征不明显,缺乏典型的发热及淋巴结肿大症状,临床上易误诊为恶性肿瘤,治疗也无标准可循。本文报道1 例喉部Rosai-Dorfman病,应用微创手术加激素治疗,保留了喉功能,取得良好疗效,并结合文献对这一罕见疾病的诊治进行探讨。
分类: 生物学 >> 生态学 提交时间: 2023-04-13 合作期刊: 《干旱区科学》
摘要:Drought, which restricts the sustainable development of agriculture, ecological health, and social economy, is affected by a variety of factors. It is widely accepted that a single variable cannot fully reflect the characteristics of drought events. Studying precipitation, reference evapotranspiration (ET0), and vegetation yield can derive information to help conserve water resources in grassland ecosystems in arid and semi-arid regions. In this study, the interactions of precipitation, ET0, and vegetation yield in Darhan Muminggan Joint Banner (DMJB), a desert steppe in Inner Mongolia Autonomous Region, China were explored using two-dimensional (2D) and three-dimensional (3D) joint distribution models. Three types of Copula functions were applied to quantitatively analyze the joint distribution probability of different combinations of precipitation, ET0, and vegetation yield. For the precipitation–ET0 dry–wet type, the 2D joint distribution probability with precipitation≤245.69 mm/a or ET0≥959.20 mm/a in DMJB was approximately 0.60, while the joint distribution probability with precipitation≤245.69 mm/a and ET0≥959.20 mm/a was approximately 0.20. Correspondingly, the joint return period that at least one of the two events (precipitation was dry or ET0 was wet) occurred was 2 a, and the co-occurrence return period that both events (precipitation was dry and ET0 was wet) occurred was 5 a. Under this condition, the interval between dry and wet events would be short, the water supply and demand were unbalanced, and the water demand of vegetation would not be met. In addition, when precipitation remained stable and ET0 increased, the 3D joint distribution probability that vegetation yield would decrease due to water shortage in the precipitation–ET0 dry–wet years could reach up to 0.60–0.70. In future work, irrigation activities and water allocation criteria need to be implemented to increase vegetation yield and the safety of water resources in the desert steppe of Inner Mongolia.
分类: 物理学 >> 核物理学 提交时间: 2023-07-12
摘要: To guarantee the exact proton dose applied to patients and ensure treatment safety while disrupting and destroying tumor cells, it is essential to accurately monitor the proton beam current in real-time during patient treatment. Because clinical treatment requires a proton beam current in the ~nA range, nondestructive beam current monitors (BCMs) are preferred to minimize the degradation of beam quality. However, this poses significant challenges in accurately monitoring such extremely low beam intensities. This study proposes a cavity-type BCM equipped with a dielectric plate to reduce its dimensions and achieve sufficient measurement sensitivity for practical requirements. A prototype cavity BCM was fabricated, and offline testing was performed using a metal wire to simulate the beam to study its performance. Both the simulation and experimental results showed that the cavity BCM could measure ultralow proton beam currents with a resolution up to 0.03 nA.
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: Molecularly thin water layer, with a hydrogen bonding network different from those in bulk water and ice, has unique properties and is generally involved in many important processes such as wetting, erosion, atmosphere chemical reaction, protein folding and biomolecular interaction. Here, we report a new water layer structure at room temperature, which is found inside nanobubbles by using synchrotron based scanning transmission soft X-ray microscopy (STXM). The three peaks 535.0, 536.8 and 540.9 eV at O K edge inside the nanobubbles show a novel characteristics of very thin water layers, which has never been observed before.
分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: In a molten salt reactor (MSR), the fuel is dissolved in fluoride salt. In this paper, the reactivity worth and reactivity initiated transient of Molten-Salt Reactor Experiment (MSRE) in the control rod failure events are analyzed. The point kinetic coupling heat-transfer model with decay character of six-group delayed neutron precursors due to the fuel motion is applied. The relative power and temperature transient under reactivity step and ramp initiated at different power levels are studied. The results show that the reactor power and temperature increase to a maximum, where they begin to decrease to stable values. Comparing with full power level, the transient result at low power level is more serious. The results are of help in our study on safety characteristics of an MSR system.
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: A unique canal (calcaneal canal) running diagonally through the calcaneus was commonly considered as characteristic for lagomorphs, both extant and fossil, but absent in rodents and other pertinent lagomorph relatives. However, our investigation of a calcaneus from the Middle Paleocene of Qianshan, Anhui Province and specimens previously grouped in Mimotonidae also shows presence of canals on calcaneus bones. To further explore the unique character, we scanned calcanei of Ordolagus, Mimolagus, Gomphos, Rhombomylus, and Oryctolagus using micro CT and investigated the calcanei of some other related taxa under microscope. Three-dimensional reconstructions of the calcanei based on CT data of these taxa confirmed the presence of apertures traversing the large medullary cavity. The diagonally oriented calcaneal canal is present not only in lagomorphs, but also in non-lagomorph duplicidentates, such as Mimotona, Gomophos, and simplicidentates, such as Rhombomylus, though smaller in size. Hence, the presence of calcaneal canal may be one of the synapomophic characters for Glires, not only for the order Lagomorpha. The shared calcaneus character confirms the close relationship between Simplicidentata and Duplicidentata.
分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2024-01-09 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: Aiming at the subband division of ultra-wide bandwidth low-frequency (UWL) signal (frequency coverage range: 704–4032 MHz) of the Xinjiang 110 m QiTai radio Telescope (QTT), a scheme of ultra-wide bandwidth signal is designed. First, we analyze the effect of different window functions such as the Hanning window, Hamming window, and Kaiser window on the performance of finite impulse response (FIR) digital filters, and implement a critical sampling polyphase filter bank (CS-PFB) based on the Hamming window FIR digital filter. Second, we generate 3328 MHz simulation data of ultra-wideband pulsar baseband in the frequency range of 704–4032 MHz using the ultra-wide bandwidth pulsar baseband data generation algorithm based on the 400 MHz bandwidth pulsar baseband data obtained from Parkes CASPSR observations. Third, we obtain 26 subbands of 128 MHz based on CS-PFB and the simulation data, and the pulse profile of each subband by coherent dispersion, integration, and folding. Finally, the phase of each subband pulse profile is aligned by non-coherent dedispersion, and to generate a broadband pulse profile, which is basically the same as the pulse profile obtained from the original data using DSPSR. The experimental results show that the scheme for the QTT UWL receiving system is feasible, and the proposed channel algorithm in this paper is effective.
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: DNA origami technique, a breakthrough in DNA nanotechnology, has been widely used to prepare complex DNA nanostructures with nanoscale addressability. However, the purity and yield are generally the bottleneck to application of DNA nanostructures, and current methods for purifying DNA origami nanostructures in large quantities are time-consuming and laborious. This study aims to develop a scalable, cost-effective and contamination-free method of purifying DNA origami nanostructures. We employ an effective and convenient purification approach to purify planar rectangle DNA origami structures through rate-zonal centrifugation. By subjecting DNA origami samples to high centrifugal force in a density gradient media of glycerol, well-folded nanostructures and by-products are separated successfully, which are confirmed by agarose gel electrophoresis and atomic force microscopy (AFM). This method will aid the production of pure rectangle DNA origami nanostructures in large quantity.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-12
摘要: Neuropeptides play a variety of roles in many physiological processes and serve as potential therapeutic targets for the treatment of some nervous-system disorders. In recent years, there has been a tremendous increase in the number of identified neuropeptides. Therefore, we have developed NeuroPep, a comprehensive resource of neuropeptides, which holds 5949 non-redundant neuropeptide entries originating from 493 organisms belonging to 65 neuropeptide families. In NeuroPep, the number of neuropeptides in invertebrates and vertebrates is 3455 and 2406, respectively. It is currently the most complete neuropeptide database. We extracted entries deposited in UniProt, the database (www.neuropeptides.nl) and NeuroPedia, and used text mining methods to retrieve entries from the MEDLINE abstracts and full text articles. All the entries in NeuroPep have been manually checked. 2069 of the 5949 (35%) neuropeptide sequences were collected from the scientific literature. Moreover, NeuroPep contains detailed annotations for each entry, including source organisms, tissue specificity, families, names, post-translational modifications, 3D structures (if available) and literature references. Information derived from these peptide sequences such as amino acid compositions, iso-electric points, molecular weight and other physicochemical properties of peptides are also provided. A quick search feature allows users to search the database with keywords such as sequence, name, family, etc., and an advanced search page helps users to combine queries with logical operators like AND/OR. In addition, user-friendly web tools like browsing, sequence alignment and mapping are also integrated into the NeuroPep database.
分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: The Chinese Academy of Science has launched a thorium-based molten-salt reactor (TMSR) research project with a mission to research and develop a fission energy system of the fourth generation. The TMSR project intends to construct a liquid fuel molten-salt reactor (TMSR-LF), which uses fluoride salt as both the fuel and coolant, and a solid fuel molten-salt reactor (TMSR-SF), which uses fluoride salt as coolant and TRISO fuel. An optimized 2 MWth TMSR-LF has been designed to solve major technological challenges in the Th-U fuel cycle. Preliminary conceptual shielding design has also been performed to develop bulk shielding. In this study, the radiation dose and temperature distribution of the shielding bulk due to the core were simulated and analyzed by performing Monte Carlo simulations and computational fluid dynamics (CFD) analysis. The MCNP calculated dose rate and neutron and gamma spectra indicate that the total dose rate due to the core at the external surface of the concrete wall was 1.91 Sv/h in the radial direction, 1.16 Sv/h above and 1.33 Sv/h below the bulk shielding. All the radiation dose rates due to the core were below the design criteria. Thermal analysis results show that the temperature at the outermost surface of the bulk shielding was 333.86 K, which was below the required limit value. The results indicate that the designed bulk shielding satisfies the radiation shielding requirements for the 2 MWth TMSR-LF.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Novel ionic binders based on sulfonated polyether ether ketones and polysulfone backbones, bearing pendant lithiated fluorinated sulfonimide groups (SPEEK-PSI-Li and PSU-PSI-Li) were developed. Their performance in high performance silicon (Si) nano-particle anodes was studied in comparison with conventional binders such as lithiated sulfonated poly(ether-ether-ketone) containing fluorinated sulfonic acid side chains (SPEEK-PSA-Li), poly(vinylidene) difluoride (PVDF), sodium carboxymethyl cellulose (CMC) and alginate. Much superior to other anode binders, the ionic conducting SPEEK-PSI-Li binders could not only provide good adhesion properties, but also effectively reduce the over-potential during rapid charge and discharge cycles. When cycled at a current of 400 mA g 1, these anodes could maintain above 2000 mA h g 1 after 50 cycles. Even when cycled at a high current rate of 2000 mA g 1, the anodes with SPEEK-PSI-Li binders could be cycled above 500 mA h g 1 in 50 cycles. The superior performance of the novel SPEEK-PSI-Li binders could be attributed to their high cohesion capability, low solubility in electrolytes, high adaptability to volume fluctuation and high ionic conducting capability resulting from of the co-existence of flexible PEEK backbones, flexible fluorinated ether side chains, ionic transporting sulfonate groups, and pentadentate super ionic sulfonimide groups in the molecule structures.
提交时间: 2017-05-02
摘要: In this paper, four types of doped ceria powders and sinters, including Gd0.1Ce0.9O1.95, Gd0.2Ce0.8O1.9, Sm0.1Ce0.9O1.95 and Sm0.2Ce0.8O1.9, are prepared and characterized. The results indicate that the Sm0.2Ce0.8O1.9 samples possess the lowest densificat