分类: 生物学 >> 生物进化论 提交时间: 2024-03-21
摘要: The affinity of ‘Dongfangaspis qujingensis’, initially assigned to Dongfangaspisbut later to Laxaspis, has long been controversial. However, the taxonomical revision raisesa new problem of junior homonym since the type species of Laxaspis is L. qujingensis. Here,we describe some new materials of ‘Dongfangaspis qujingensis’ and Damaspis vartus fromthe Xishancun Formation (early Lochkovian, Early Devonian) in Qujing, Yunnan Province.‘Dongfangaspis qujingensis’ strikingly resembles Damaspis vartus in the slightly longerheadshield, bifurcated ends of the lateral transverse canals, unconnected V-shaped posteriorsupraorbital canals, and at least seven pairs of lateral transverse canals issuing from the lateraldorsal canal. These similarities indicate that ‘D. qujingensis’ is more suggestive of Damaspis thanDongfangaspis and Laxaspis. Therefore, we propose to remove ‘Dongfangaspis qujingensis’ fromLaxaspis to Damaspis. The new specimens of Damaspis vartus reveal five long lateral transversecanals on the right side, corroborating that the asymmetric sensory canal system in the holotype isthe intraspecific variation.
分类: 生物学 >> 动物学 提交时间: 2020-09-15 合作期刊: 《古脊椎动物学报》
摘要: Neogene strata rich in fossil mammals are well exposed in central Nei Mongol, China. Over a dozen mammalian faunas in chronological succession from Early Miocene to Early Pliocene were discerned in this region, and they built a fundamental part of the Neogene land mammal biochronological system in northern China. Tuchengzi was first recognized for producing abundant mammalian fossils during the Sino-Soviet Paleontological Expedition (SSPE) initiated in 1959. However, all unearthed fossils from the SSPE were either large- or middle-sized mammals, and small mammal fossils in the Tuchengzi Fauna were deficient for a long time. The composition and biochronological position of the Tuchengzi Fauna in the Neogene mammalian biochronological system in northern China was not particularly clear. The new fossils here reported are represented by 6 taxa of small mammals. Based on the co-occurrence of Lophocricetus grabaui, Sinocricetus zdanskyi, Prosiphneus licenti, Hansdebruijnia pusilla, and Moschus grandaevus, the age of the Tuchengzi Fauna is constrained to late Late Miocene or Baodean Chinese Land Mammal Age, slighter younger than the Baogeda Ula Fauna and older than the Ertemte Fauna. Judging from the fossil composition, the Tuchengzi Fauna possibly inhabited a forest-steppe mixed habitat during the late Late Miocene.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2023-05-31
摘要: Carbon-ion radiotherapy (CIRT) offers unique physical and biological advantages over photon radiotherapy. However, somematerials and devices in the CIRT treatment room become radioactive under bombardment by therapeutic carbon-ion beamsdue to nuclear reactions, thereby leading to possible radiation hazards to medical staff and additional and unwanted dosesto patients. This study assessed the level of induced radioactivity in the treatment room of the Heavy-Ion Medical Machine(HIMM) in Wuwei. Monte Carlo simulations using PHITS were performed for a conservative case under the conditions ofmaximum beam energy and intensity provided by the HIMM facility. The geometry and configuration of Treatment Room2 of the HIMM facility in Wuwei were adopted. We evaluated the activation of air, the phantom, and the components ofthe beamline, such as the primary collimator (PC), ridge filter (RF), and multileaf collimator (MLC). For air activation,we calculated the medical staff immersion external exposure and inhalation internal exposure caused by the correspondingradionuclides. For phantom activation, we estimated the additional dose to the patients family members owing to secondaryphotons after treatment. In addition, the exemption or non-exemption of the component material activation was assessed.The results showed that external radiation caused by air activation was the main source of the annual effective dose atapproximately 0.5mSv/y. The induced radioactivity exposure to family members of a patient after CIRT was approximately40Sv, sufficiently lower than the public dose limit of 1mSv/a. The induced radioactivity of the PC, RF, and MLC was allabove the exempt levels after the devices were retired, whereas the induced radioactivity of the RS and compensator couldreach the exempt levels after one patient session. Our study indicated that medical staff engaged in CIRT should stay awayfrom the high-dose-rate area of induced radioactivity along the beam direction, shorten the residence time in the treatmentroom as much as possible, and store the activated components in isolation after the equipment is out of use. Thus, this studyprovides guidance for accurately assessing the level of induced radioactivity in the treatment room for CIRT.
分类: 生物学 >> 动物学 提交时间: 2019-06-17 合作期刊: 《古脊椎动物学报》
摘要: We reconstructed a wealth of three-dimensional virtual models of vertebrate microremains from the Xitun Formation and lower part of the Xishancun Formation (Lochkovian,Lower Devonian) of Qujing, Yunnan by means of high-resolution computed tomography. One genus (Parathelodus) and seven species (P. trilobatus, P. asiaticus, P. cornuformis, P. scitulus, P. xitunensis sp. nov., P. wangi sp. nov. and P. liaokuoensis sp. nov.) of thelodonts are described. The new discovery extends the stratigraphic distribution of Parathelodus from the Xitun Formation and the upper part of the Xishancun Formation to the lower part of the Xishancun Formation, the horizon close to the Silurian-Devonian boundary. The three new species, P. xitunensis, P. wangi and P. liaokuoensis, enhance our knowledge of the thelodont diversity from the Early Devonian of China.
分类: 核科学技术 >> 核科学与技术 提交时间: 2023-08-27
摘要: Intensity-modulated particle therapy (IMPT) with carbon ions is comparatively susceptible to various uncertainties caused by breathing motion, including range, setup, and target positioning uncertainties. To determine relative biological effectiveness-weighted dose (RWD) distributions that are resilient to these uncertainties, the reference phase-based four-dimensional (4D) robust optimization (RP-4DRO) and each phase-based 4D robust optimization (EP-4DRO) method in carbon-ion IMPT treatment planning were evaluated and compared. Based on RWD distributions, 4DRO methods were compared with 4D conventional optimization using planning target volume (PTV) margins (PTV-based optimization) to assess the effectiveness of the robust optimization methods. Carbon-ion IMPT treatment planning was conducted in a cohort of five lung cancer patients. The results indicated that the EP-4DRO method provided better robustness (P=0.080) and improved plan quality (P=0.225) for the clinical target volume (CTV) in the individual respiratory phase when compared with the PTV-based optimization. Compared with the PTV-based optimization, the RP-4DRO method ensured the robustness (P = 0.022) of the dose distributions in the reference breathing phase, albeit with a slight sacrifice of the target coverage (P=0.450). Both 4DRO methods successfully maintained the doses delivered to the organs at risk (OARs) below tolerable levels, which were lower than the doses in the PTV-based optimization (P<0.05). Furthermore, the RP-4DRO method exhibited significantly superior performance when compared with the EP-4DRO method in enhancing overall OAR sparing in either the individual respiratory phase or reference respiratory phase (P<0.05). In general, both 4DRO methods outperformed the PTV-based optimization in terms of OAR sparing and robustness.
分类: 天文学 >> 天文学 提交时间: 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: The development of spectroscopic survey telescopes like Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), Apache Point Observatory Galactic Evolution Experiment and Sloan Digital Sky Survey has opened up unprecedented opportunities for stellar classification. Specific types of stars, such as early-type emission-line stars and those with stellar winds, can be distinguished by the profiles of their spectral lines. In this paper, we introduce a method based on derivative spectroscopy (DS) designed to detect signals within complex backgrounds and provide a preliminary estimation of curve profiles. This method exhibits a unique advantage in identifying weak signals and unusual spectral line profiles when compared to other popular line detection methods. We validated our approach using synthesis spectra, demonstrating that DS can detect emission signals three times fainter than Gaussian fitting. Furthermore, we applied our method to 579,680 co-added spectra from LAMOST Medium-Resolution Spectroscopic Survey, identifying 16,629 spectra with emission peaks around the Hα line from 10,963 stars. These spectra were classified into three distinct morphological groups, resulting in nine subclasses as follows. (1) Emission peak above the pseudo-continuum line (single peak, double peaks, emission peak situated within an absorption line, P Cygni profile, Inverse P Cygni profile); (2) Emission peak below the pseudo-continuum line (sharp emission peak, double absorption peaks, emission peak shifted to one side of the absorption line); (3) Emission peak between the pseudo-continuum line.
分类: 生物学 >> 动物学 提交时间: 2023-07-12 合作期刊: 《古脊椎动物学报》
摘要: The Shuitangba subbasin lignite deposits of the Zhaotong Basin in northern Yunnan Province have produced vertebrate fossils of terminal Miocene age. We conducted test wet screening of fossiliferous sediment in 2014 to increase representation of small mammals. This effort produced four teeth of a very large bamboo rat, much larger than the previously known bamboo rat present at Shuitangba, and representing a new species. This new species is characterized by its molars being remarkably larger than those of other known species of Miorhizomys, and being hypsodont with cementum, and less anterorposteriorly compressed. The age of this new species from Shuitangba is in the range of 6.2 to 6.7 Ma. It appears that diverse bamboo rats of the extinct genus Miorhizomys were present in the Late Miocene of Yunnan, somewhat before the 6 Ma appearance of extant Rhizomys to the north in the vicinity of Shanxi Province.
分类: 生物学 >> 动物学 提交时间: 2022-04-16 合作期刊: 《古脊椎动物学报》
摘要: A new genus and species of the family Eugaleaspidae (Eugaleaspiformes, Galeaspida), Xitunaspis magnus gen. et sp. nov., is described from the Lower Devonian Xitun Formation in Qujing, Yunnan Province, China. The new genus displays the diagnostic characters of the Eugaleaspidae, including a slit-like median dorsal opening, no inner cornual process, developed median dorsal canals, and only three pairs of lateral transverse canals extending from lateral dorsal canals. Different from the other eugaleaspids, X. magnus possesses a large headshield with thick dermal bone and a more plesiomorphic sensory canal system. The phylogenetic analysis of the Galeaspida reveals that Xitunaspis clusters with Dunyu and Eugaleaspis to form a monophyletic clade Eugaleaspidae Liu, 1965, and has a closer relationship with Dunyu than Eugaleaspis by sharing the thick dermal bone of the headshield. The new finding represents the first convincing fossil record of the Eugaleaspiformes in the middle Lochkovian Xitun Formation and adds to our knowledge about the morphology of eugaleaspiforms and the evolutionary pattern of the sensory canal system in the Eugaleaspiformes and even Galeaspida.
提交时间: 2017-05-02
摘要: Proton-conducting graphene oxide electrolyte films with very high electric-double-layer capacitance are used as the gate dielectrics for oxide-based neuron transistor fabrication. Paired-pulse facilitation, dendritic integration, and orientation tuning ar
提交时间: 2017-05-02
摘要: Laterally coupled indium-zinc-oxide electric-double-layer [EDL] transistors gated by solution-processed sodium alginate electrolyte films are self-assembled on glass substrates. Due to the strong EDL effect, a low-operation voltage of 1.5 V, a high-curren