分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-06-27
摘要： With the assistance of two extra groups, i.e., an extra hidden gauge group SU(2)(D) and a global U(1) group, we propose a two component dark matter (DM) model. After the symmetry SU(2)(D) x U(1) being broken, we obtain both the vector and scalar DM candidates. The two DM candidates communicate with the standard model (SM) via three Higgs as multi-Higgs portals. The three Higgs are mixing states of the SM Higgs, the Higgs of the hidden sector and real part of a supplement complex scalar singlet. We study relic density and direct detection of DM in three scenarios. The resonance behaviors and interplay between the two component DM candidates are represented through investigating of the relic density in the parameter spaces of the two DMs masses. The electroweak precision parameters constrains the two Higgs portals couplings (lambda(m) and delta(2)). The relevant vacuum stability and naturalness problem in the parameter space of lambda(m) and delta(2) are studied as well. The model could alleviate these two problems in some parameter spaces under the constraints of electroweak precision observables and Higgs indirect search.
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： Shanshenmiaozui site in Nihewan Basin in North China is a recently discovered Early Pleistocene site which yields rich and diverse mammalian fossils. In the fauna, the small and medium-sized bovid fossils are well represented and can be referred to the following taxa: Spirocerus wongi, Gazella sinensis, Ovis shantungensis and Megalovis piveteaui respectively, among which G. sinensis is the dominate species. S. wongi and G. sinensis are mainly represented by horn-cores and partial skull bones as well as mandibles; in addition, metacarpal and/or metatarsal bones were also recognized for all of the four species. The horn-cores are easy to be identified to the species level, while the dentitions and the postcranial bones underwent a series of examinations and comparisons before getting properly determined and referred to the most approximate taxa. Among the postcranial bones, the metapodials, especially to the metacarpal bones special attentions were paid, which are crucial not only for taxonomic identification, but also for phylogenetic and paleoecological reconstructions; the previously misidentified metapodial specimens in Nihewan fauna were reconsidered in this paper. In the SSMZ fauna, the bovid guild is dominated by Gazella and Bison, which indicates steppe was the most important biome in Nihewan Basin during Early Pleistocene.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： We search for the ψ(4S) state in $B^\pm \ra \eta J/\psi K^\pm$ and $e^+e^- \ra \eta J/\psi$ based on the Belle measurements with the assumed mass M=(4230±8) MeV/c2 and width Γ=(38±12) MeV. No significant signal is observed in the ηJ/ψ mass spectra. The 90\% confidence level upper limit on the product branching fraction $\BR(B^\pm \ra \psi(4S)K^\pm)\BR(\psi(4S) \ra \eta J/\psi)<6.8\times 10^{-6}$ is obtained in$B^\pm \ra \eta J/\psi K^\pm$ decays. By assuming the partial width of ψ(4S)→e+e− being 0.63 keV, the branching fraction limit $\BR(\psi(4S) \ra \eta J/\psi) < 1.3\%$ is obtained at the 90\% confidence level in$e^+e^- \ra \eta J/\psi$, which is consistent with the theoretical prediction.
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： As a potential matrix of three-dimensional gel dosimeter, agarose hydrogels will be used for measuring radiation doses, hence the importance of studying their radiation resistance and radiolysis mechanism. Physical property and chemical structure of physically cross-linked agarose hydrogel samples irradiated to 0200 kGy by 60Co -rays were analyzed by universal testing machine, gel permeation chromatography, fourier transform infrared spectrometer, ultraviolet visible spectroscopy, nuclear magnetic resonance, and gas chromatography. The results showed that agarose hydrogels had good radiation stability below 25 kGy, and the maximum compression strength of sample was ca. 0.1 MPa at 25 kGy. The irradiated samples degraded obviously and liquefied gradually with increasing doses. Compared with unirradiated sample, carbonyl groups, which generated from the molecular chains of agarose hydrogels, were observed at 25 kGy and increased gradually with dose. The main gas products evolved from irradiated agarose hydrogels were H2, CO2, CO and CH4. Based on the analysis of radiolytic products, the radiolysis mechanism of agarose hydrogels under -radiation was proposed.
分类： 生物学 >> 生物学其他学科 提交时间： 2018-07-18 合作期刊: 《古脊椎动物学报》
摘要： Here we discribe a new ootypes of prismatoolithids found from the Late Cretaceous Jiangjunding Formation in the Laiyang Basin, Shandong Province. On the basis of characters such as elongate ovoids, smooth eggshell surface, relatively thinner eggshell thickness, prismatic eggshell units, slender pores in radial section of eggshell and little pores with round or irregular shapes in tangeital section of eggshell, we erect one new oogenus and one new oospecies: Laiyangoolithus lixiangensis oogen. et oosp. nov. The discovery of L. lixiangensis not only enriches the diversity and composition of the Laiyang Dinosaur Egg Fauna, but the paleogeographic distribution of primatoolithids as well. In addition, it provides more paleontological materials for the study of the diversity and paleogeographic distribution of troodontids in China.
分类： 化学 >> 物理化学 提交时间： 2017-11-05 合作期刊: 《结构化学》
摘要： In this work, we perform DFT + U periodic calculations to study geometrical and electronic structures and oxygen vacancy formation energies of SmxCayCe1-x-yO2-δ systems (x = 0.0312, 0.0625, 0.125 and 0.250; y = 0.0312, 0.0625, 0.125 and 0.250; δ = 0.0312, 0.0625, 0.125, 0.250 and 0.50) with different oxygen vacancy and doping concentrations. The calculated results show that the V1-Sm3+-V2 structures where there is a position relationship of the face diagonal between V1 and V2 both nearest to Sm3+ have the lowest energy configurations. The study on electronic structures of the SmxCayCe1-x-yO2-δ systems finds that excess electrons arise from oxygen vacancies and are localized on f-level traps of their neighbor Ce, and Ca2+ and Sm3+ co-doping effectively restrains the reduction of Ce4+. In order to avoid the existence of Ce3+, x and y must be both larger than 0.0625 as δ = 0.125 or δ must be smaller than 0.125 as x = y = 0.0625. The Ce3+/Ce4+ change ratio k has an obvious monotonous increase with increasing the vacancy oxygen concentration. The introduction of Sm3+ decreases k. In addition, the doped Sm3+ can restrain the reduction of Ce4+ when the V1-Sm3+-V2 structure with a face diagonal position relationship in lower reduced atmosphere exists. It need be pointed out that the Sm0.25Ce0.75O1.5 system should be thought of as a Sm-doped Ce2O3 one.
分类： 生物学 >> 人类学 提交时间： 2024-03-06
摘要： The inference of Mesozoic avialan bird diets previously relied on traditional methods such as morphological comparisons among taxa and direct evidence such as identifiable stomach contents. However, the application of these approaches has been limited because of uncommon preservation of relevant fossil evidence. We searched for additional informative characteristics to help develop new methods to assess the diet of fossil birds. In particular, the morphology of the avialan neck is highly modularized and plays roles in multiple functions including food acquisition. The structure of and variation among the cervical vertebrae likely reflects the demands of feeding ecology in fossil and extant birds because the avialan neck evolved to, at least in part, replace the forelimbs by assisting with activities such as cranioinertial feeding and other ecological functions. Here, we utilize morphometric and statistical analyses to establish an initial quantitative relationship between cervical morphology and dietary modes in both extant and extinct birds. This morphometric framework derived from the cervical morphology of living birds is used as a basis to estimate the diet categories of five taxa of Mesozoic birds. The results indicate that there is a quantitative correlation between cervical morphology differentiation and their interrelated feeding modes. The enantiornithine taxa examined exhibit cervical morphologies similar to extant insectivorous or carnivorous birds. The ornithurine species show cervical morphologies that are more aligned with generalist or herbivorous birds, and exhibit preliminary morphological features tied to aquatic adaptions. These findings are consistent in part with other direct fossil evidence, as well as hypotheses developed from other skeletal comparisons. Therefore, the cervical vertebral series, as a skeletal system closely linked to food acquisition, can serve as one of the valuable metrics to provide information for inferring the diet of long extinct Mesozoic birds.
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 gel dosimeter has the uniquely capacity in recording radiation dose distribution in three dimensions (3D), which has the specific advantages in dosimetry measurements where steep dose gradients exist. In this study, a novel radiochromic gel dosimeter was developed by dispersing nanovesicles self-assembled by 10, 12-pentacosadiynoic acid (PCDA) into the tissue equivalence gel matrix. The characteristics of radiochromic PCDA vesicle gel dosimeters were evaluated. Results indicate that these radiochromic gel dosimeters have good linear response to 1.7 MeV electron beam irradiation in the dose range of 0.326.36 kGy. In addition, the radiochromic gel dosimeters overcome the limitations of the existing gel dosimeters such as diffusion effect, post-radiation effect, and poor forming ability. Hence, the radiochromic PCDA vesicle gel dosimeters developed could be generally applied to 3D dose distribution measurement with optical readout.
分类： 生物学 >> 动物学 提交时间： 2021-11-26 合作期刊: 《古脊椎动物学报》
摘要： The aardwolf Proteles cristatus is the only known hyaenid, living or extinct, to exhibit an extremely reduced dentition related to its termite-specializing diet. The fossil record of extant aardwolves extends to 2 to 4 million years ago, but records that inform its evolutionary origins are essentially nonexistent. Such circumstance renders it difficult to place this unusual hyena in the broader evolutionary context of small-bodied hyaenid species in Eurasian Neogene deposits. Here we describe a new genus and species of a small-bodied hyaenid, Gansuyaena megalotis, representing the closest morphological link to aardwolves to date. This new fossil hyena is based on a skull with associated mandible, a rostrum preserving several teeth, and several referred specimens. The new specimens were discovered in Neogene deposits in Linxia Basin, Gansu Province, China. Phylogenetic analysis indicates that among early hyaenids, G. megalotis is most closely related, but unlikely ancestral, to the living aardwolf. Also recognized in this new species are the fossils previously referred to “Protictitherium” aff. P. gaillardi from Pasalar, Turkey. Additionally, “Plioviverrops” guerini from Los Mansuetos, Spain is interpreted to represent a second Gansuyaena species. In addition to the living aardwolf, Proteles cristatus, our analyses suggest that the proteline lineage includes the extinct genera Gansuyaena, Mesoviverrops, and Plioviverrops. Although the precise timing and geographic location of evolutionary divergence between the aardwolf and Gansuyaena remain elusive, critical new morphological information provided by Gansuyaena specimens reinforce findings from recent genomic analyses that the aardwolf lineage has an ancient origin from small-bodied stem hyaenids prior to the appearance of large and robust bone-cracking hyaenines.
分类： 生物学 >> 动物学 提交时间： 2020-03-31 合作期刊: 《古脊椎动物学报》
摘要： An adult amynodont skull, collected from the Middle Eocene Niezhuang Formation of Jiyuan Basin (Henan, China), is recognized as a new species Amynodontopsis jiyuanensis sp. nov. The specimen possesses the typical features of the genus Amynodontopsis, such as a dolichocephalic skull with elevated roof, premaxilla-nasal contact, large preorbital fossa extending posteriorly medial to the orbit, inner surface of anterior orbital bar concave in continuation with the preorbital fossa, antecrochet usually presented on M1, and metastyle of M3 strongly deflected labially. A. jiyuanensis is diagnosed by a combination of the following characters: long nasals, nasal process of premaxilla extending far back laterally below the nasal and excluding the maxilla from the border of external nares, nasal notch above the post-canine diastema, more transverse and proportionally longer protoloph and metaloph on upper molars. Comparison with known species of Amynodontopsis indicates that it is the most primitive one in the genus, due to the possession of primitive characters. Associated fossil mammals support a correlation of the strata bearing A. jiyuanensis with the Shara Murun Formation of the Erlian Basin, Nei Mongol, China, namely the Middle Eocene Sharamurunian Asian Land Mammal Age (ALMA), prior to all other known Amynodontopsis species. The earlier geologic age and primitive morphological features of A. jiyuanensis suggest that Amynodontopsis has an Asian origin in the Middle Eocene and later immigrated into North America.
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： Neutron spectrum should be measured before test samples are irradiated. Neutron spectrum in an irradiation chamber of a research reactor was measured by using activation method when the reactor is in normal operation under 2 MW. Sixteen kinds of non-fission foils (19 reaction channels) were selected, of which 10 were sensitive to thermal and intermediate energy regions, while the others were of different threshold energy and sensitive to fast energy regions. By measuring the foil radioactivity, the neutron spectrum was unfolded with the iterative methods SAND-II and MSIT. Finally, shielding corrections of group cross-section and main factors affecting the calculation accuracy were studied and the uncertainty of solution was analyzed using the Monte Carlo method in the process of SAND-II.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： Single event upsets (SEUs) induced by heavy ions were observed in 65 nm SRAMs to quantitatively evaluate the applicability and effectiveness of single-bit error correcting code (ECC) utilizing Hamming Code. The results show that the ECC did improve the performance dramatically, with the SEU cross sections of SRAMs with ECC being at the order of 10-11 cm2/bit, two orders of magnitude higher than that without ECC (at the order of 10-9 cm2/bit). Also, ineffectiveness of ECC module, including 1-, 2- and 3-bits errors in single word (not Multiple Bit Upsets), was detected. The ECC modules in SRAMs utilizing (12, 8) Hamming code would lose work when 2-bits upset accumulates in one codeword. Finally, the probabilities of failure modes involving 1-, 2- and 3-bits errors, were calcaulated at 39.39%, 37.88% and 22.73%, respectively, which agree well with the experimental results.
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： Here we briefly review the history of research on the Laiyang dinosaur and dinosaur egg faunas, summarize the contributions of C. C. Young and other elder paleontologists to the discoveries of the Late Cretaceous dinosaurs and dinosaur eggs from Laiyang, and introduce the new discoveries and the advances in the research on the Laiyang faunas. The new investigations in Laiyang from 2008 have found a series of valley developed in plain and more than ten new dinosaur or dinosaur egg fossil beds. In 2010, we began the massive excavations at two localities in Jingangkou and collected abundant dinosaurs and other vertebrate fossils, such as a new saurolophine, some theropod material and a new taxon of turtle egg. The bone beds in Locality 2 with the typical sedimentary and burial patterns of mudflow, and these fossil deposits are interpreted as having been carried and deposited by mudflow. The re-observation and the CT scanning data of the crest of Tsintaosaurus spinorhinus (IVPP V 725) show that the crest is fractured and solid. However, based on the re-observations of its cranial and postcranial specimens, we consider that Tsintaosaurus spinorhinus is a valid taxon of lambeosaurines, which have the hollow crest. Therefore, the crest of Tsintaosaurus might not belong to the skull of this individual, and the true form of the crest needs to be confirmed in the future work. We reassess the three species of Tanius, and obtain several results. 1) Tanius sinensis and Tanius chingkankouensis are the valid species of Tanius; 2) Tanius laiyangensis is invalid.; 3) the sacrum and ilium of Tanius chingkankouensis with typical hadrosaurid features should not be referred to Tanius.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-05
Wang, Xianlong
Cao, Chunwei
Huang, Jiaojiao
Yao, Jing
Hai, Tang
Zheng, Qiantao
Wang, Xiao
Zhang, Hongyong
Qin, Guosong
Zhou, Qi
Wang, Hongmei
Zhao, Jianguo
Zheng, Qiantao
Wang, Xiao
Zhang, Hongyong
Zhou, Qi
Wang, Hongmei
Zhao, Jianguo
Cheng, Jinbo
Yuan, Zengqiang
摘要： Pig shows multiple superior characteristics in anatomy, physiology, and genome that have made this species to be more suitable models for human diseases, especially for neurodegenerative diseases, because they have similar cerebral convolutions compared with human neocortex. Recently, CRISPR/Cas9 system shows enormous potential for engineering the pig genome. In this study, we expect to generate human Parkinson's disease pig model using CRISPR/Cas9 system by simultaneously targeting three distinct genomic loci, parkin/DJ-1/PINK1, in Bama miniature pigs. By co-injection of Cas9 mRNA and multiplexing single guide RNAs (sgRNAs) targeting parkin, DJ-1, and PINK1 genes, respectively, into in vivo derived pronuclear embryos, we simultaneously targeted three distinct genomic loci. The gene modified piglets remain healthy and display normal behavior at the age of 10 months. In addition, despite the high number of sgRNAs were employed in the present study, our trio-based whole-genome sequencing analysis suggested that the incidence of off-target events is low. Our results demonstrate that the simplicity, efficiency, and power of the CRISPR/Cas9 system to allow for the modification of multiple genes in pigs and yield results of high medical value.
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： 2022-08-02 合作期刊: 《古脊椎动物学报》
摘要： 报道了哈密南湖戈壁首次发现的恐龙蛋，包括长形长形蛋(Elongatoolithus elongatus)和椭圆形蛋未定种(Ovaloolithus oosp.)。这些恐龙蛋的发现不仅扩展了长形蛋类和椭圆形蛋类的古地理分布，而且表明南湖戈壁含蛋岩层地质时代为晚白垩世末期；该地层是否可与吐鲁番盆地的苏巴什组进行对比还有待进一步工作确认
分类： 生物学 >> 动物学 提交时间： 2022-01-19 合作期刊: 《古脊椎动物学报》
摘要： Moganopterus zhuiana L�et al. 2012 was erected as a member of the Boreopteridae, which was questioned by different researchers shortly after the publication. Although the new assignment to the Ctenochasmatidae is widely accepted by pterosaur researchers, some characteristics still require a detailed description. Here, the holotype of this taxon is restudied, and some ambiguous characteristics are re-identified. The diagnosis of this taxon has been revised as the following: a large ctenochasmatid pterosaur, which can be distinguished from other members of this clade by a single autapomorphy: an elongated rod-like parietal crest that extends posterodorsally, forming an angle of about 15�with the ventral margin of the skull. This taxon can be further distinguished from other ctenochasmatids on the basis of the following combination of characteristics: straight occlusal surfaces of the upper and low jaws; presence of a low premaxillary crest confined anterior to the nasoantorbital fenestra; rostrum about two thirds of the skull length; nasoantorbital fenestra occupying slightly more than 20% of the skull length; about 100 slender teeth; and a mid-cervical length/width ratio of about 7. The wingspan of M. zhuiana has been re-estimated according to a simple regression equation for wingspan versus skull length in ctenochasmatids. It confirms that M. zhuiana, although smaller than previous thought, is still the largest known ctenochasmatid. When comparing the sizes of ctenochasmatids in the Jurassic and Cretaceous, ctenochasmatids showed a rough tendency to increase their sizes.
分类： 地球科学 >> 地质学 提交时间： 2017-08-10 合作期刊: 《古脊椎动物学报》
摘要： We provide a complete description of the skeletal anatomy of the holotype of Chiappeavis magnapremaxillo, the first enantiornithine to preserve a rectricial fan, suggesting that possibly rectricial bulbs were present in basal members of this clade. Notably, Chiappeavis preserves a primitive palatal morphology in which the vomers reach the premaxillae similar to Archaeopteryx but unlike the condition in the Late Cretaceous enantiornithine Gobipteryx. If rectricial bulbs were present, pengornithid pygostyle morphology suggests they were minimally developed. We estimate the lift generated by the tail fan preserved in this specimen and compare it to the tail fans preserved in other Early Cretaceous birds. Aerodynamic models indicate the tail of Chiappeavis produced less lift than that of sympatric ornithuromorphs. This information provides a possible explanation for the absence of widespread aerodynamic tail morphologies in the Enantiornithes. 契氏鸟(Chiappeavis)是首次发现保存有扇状尾羽的反鸟类，显示出尾羽球茎这一结构在较原始的反鸟类中已经发育。详细描述了巨前颌契氏鸟(C. magnapremaxillo)正型标本的骨骼形态学特征。契氏鸟的腭区形态与始祖鸟(Archaeopteryx)相似，而区别于晚白垩世的反鸟类戈壁鸟(Gobipteryx)。即使具有尾羽球茎，鹏鸟类的尾综骨形态也表明该结构发育较差。估算了在契氏鸟中由扇状尾羽所产生的浮力，并与其他早白垩世鸟类进行对比。结果显示，契氏鸟的扇状尾羽所产生的空气浮力小于同时代生活的今鸟型类，这有可能解释了反鸟类中具有空气动力学功能的尾羽形态普遍缺乏的现象。
分类： 地球科学 >> 地质学 提交时间： 2017-08-10 合作期刊: 《古脊椎动物学报》
摘要： Here we briefly review the history of research on the Laiyang dinosaur and dinosaur egg faunas, summarize the contributions of C. C. Young and other elder paleontologists to the discoveries of the Late Cretaceous dinosaurs and dinosaur eggs from Laiyang, and introduce the new discoveries and the advances in the research on the Laiyang faunas. The new investigations in Laiyang from 2008 have found a series of valley developed in plain and more than ten new dinosaur or dinosaur egg fossil beds. In 2010, we began the massive excavations at two localities in Jingangkou and collected abundant dinosaurs and other vertebrate fossils, such as a new saurolophine, some theropod material and a new taxon of turtle egg. The bone beds in Locality 2 with the typical sedimentary and burial patterns of mudflow, and these fossil deposits are interpreted as having been carried and deposited by mudflow. The re-observation and the CT scanning data of the crest of Tsintaosaurus spinorhinus (IVPP V 725) show that the crest is fractured and solid. However, based on the re-observations of its cranial and postcranial specimens, we consider that Tsintaosaurus spinorhinus is a valid taxon of lambeosaurines, which have the hollow crest. Therefore, the crest of Tsintaosaurus might not belong to the skull of this individual, and the true form of the crest needs to be confirmed in the future work. We reassess the three species of Tanius, and obtain several results. 1) Tanius sinensis and Tanius chingkankouensis are the valid species of Tanius; 2) Tanius laiyangensis is invalid.; 3) the sacrum and ilium of Tanius chingkankouensis with typical hadrosaurid features should not be referred to Tanius. 简要回顾了莱阳恐龙和恐龙蛋化石群的研究历史和以杨钟健为代表的老一代地质古生物学者对莱阳恐龙和恐龙蛋研究和发现的杰出贡献，并介绍了莱阳恐龙和恐龙蛋的最新发现和若干研究进展。在近年来对莱阳周边地层进行的大规模考察中，发现了一系列发育在平原上的恐龙峡谷群；以及其中蕴含的十几个恐龙和恐龙蛋新地点和新层位。2010年开始，在对莱阳金岗口村附近的2个化石地点的发掘中，发现了以鸭嘴龙科为主的大量脊椎动物化石和蛋化石，包括一类新的栉龙亚科成员，一些大型兽脚类恐龙化石，以及一新的龟鳖类蛋化石等。2号地点化石富集层具有典型的泥石流沉积特征和骨骼埋藏特征。对棘鼻青岛龙的特殊头饰进行了CT扫描和三维重建，发现其头饰是实心结构，但其他骨骼特征证明棘鼻青岛龙属于具有头饰的赖氏龙亚科是确定无疑的，所以目前发现的头饰应不是其真实状态或根本不属于其头部骨骼。此外，对谭氏龙1属3种的重新观察研究得出以下结论：中国谭氏龙和金刚口谭氏龙应是有效属种，但部分骨骼还有疑问，还需要进一步研究，而莱阳谭氏龙为无效属种。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2021-12-31
摘要： The muon radiography imaging technique for high-atomic-number objects (Z) and large-volume objects via muon transmission imaging and muon multiple scattering imaging remains a popular topic in the field of radiation detection imaging. However, few imaging studies have been reported on low and medium Z objects at the centimeter scale. This paper presents an imaging system that consists of three layers of a position-sensitive detector and four plastic scintillation detectors. It acquires data by coincidence detection technique of cosmic-ray muon and its secondary particles. A 3D imaging algorithm based on the density of the coinciding muon trajectory was developed, and 4D imaging that takes the atomic number dimension into account by considering the secondary particle ratio information was achieved. The resultant reconstructed 3D images could distinguish between a series of cubes with 5-mm side lengths and 2-mm intervals. If the imaging time is more than 20 days, this method can distinguish intervals with a width of 1 mm. The 4D images can specify target objects with low, medium, and high Z values.
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