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71.
Xu X  Wang K  Zhang K  Ma Q  Xing L  Sullivan C  Hu D  Cheng S  Wang S 《Nature》2012,484(7392):92-95
Numerous feathered dinosaur specimens have recently been recovered from the Middle-Upper Jurassic and Lower Cretaceous deposits of northeastern China, but most of them represent small animals. Here we report the discovery of a gigantic new basal tyrannosauroid, Yutyrannus huali gen. et sp. nov., based on three nearly complete skeletons representing two distinct ontogenetic stages from the Lower Cretaceous Yixian Formation of Liaoning Province, China. Y. huali shares some features, particularly of the cranium, with derived tyrannosauroids, but is similar to other basal tyrannosauroids in possessing a three-fingered manus and a typical theropod pes. Morphometric analysis suggests that Y. huali differed from tyrannosaurids in its growth strategy. Most significantly, Y. huali bears long filamentous feathers, thus providing direct evidence for the presence of extensively feathered gigantic dinosaurs and offering new insights into early feather evolution.  相似文献   
72.
刘锐平  Nan  Jun  Li  Xing  Yang  Yanling  Xia  Shengji  Li  Guibai 《高技术通讯(英文版)》2006,12(1):77-81
Effectiveness of hydrous manganese dioxide (δMnO2) adsorbing humic acid under different conditions and its subsequent effects on trihalomethane (THMs) formation have been studied. Humicacid removal increases with higher pH and residual TOC decreases from 3.63 mg/L to 1.68 mg/L with pH increasing from 5.5 to 8.5 at 3.0 mg/L δMnO2; δMnO2 exhibits good potential of removing humic acid and the adsorbing potential as high as 1 mg TOC/mg δMnO2 is achieved; the fractional reduction of humic acid with higher molecular weight is about 30% higher than that with lower molecular weight. δMnO2 adsorption obviously reduces subsequent THMs formation; more significant THMs formation reduction is observed for humic acid with higher molecular weight. δMnO2 adsorption is an important factor that contributes to humic acid removal and THMs formation reduction in permanganate pre-oxidation process.  相似文献   
73.
建立了主动控制起落架系统的非线性模型和控制方程,对系统进行了稳定性分析,应用simulink对起落架主动控制系统进行了仿真,结果表明通过应用主动控制起落架系统,减小了飞机重心的垂直位移和起落架传递给机身的载荷,对提高飞机的滑行品质、提高乘客的舒适性、改善民用飞机在低等级机场上以及军用飞机在修复类或损坏类跑道上的使用等有着重要的意义。  相似文献   
74.
Nonalcoholic fatty liver disease (NAFLD) is a burgeoning health problem of unknown etiology that varies in prevalence among ancestry groups. To identify genetic variants contributing to differences in hepatic fat content, we carried out a genome-wide association scan of nonsynonymous sequence variations (n = 9,229) in a population comprising Hispanic, African American and European American individuals. An allele in PNPLA3 (rs738409[G], encoding I148M) was strongly associated with increased hepatic fat levels (P = 5.9 x 10(-10)) and with hepatic inflammation (P = 3.7 x 10(-4)). The allele was most common in Hispanics, the group most susceptible to NAFLD; hepatic fat content was more than twofold higher in PNPLA3 rs738409[G] homozygotes than in noncarriers. Resequencing revealed another allele of PNPLA3 (rs6006460[T], encoding S453I) that was associated with lower hepatic fat content in African Americans, the group at lowest risk of NAFLD. Thus, variation in PNPLA3 contributes to ancestry-related and inter-individual differences in hepatic fat content and susceptibility to NAFLD.  相似文献   
75.
Acer is an important genus in temperate forests in Northeast China.Individual Acer trees can re-sprout from the root collar and can occur in clonal units,either as a single-stemmed or multi-stemmed tree.However,the factors that induce multiple-stems in Acer remain only partly understood.In this study,we determined the relative importance of abiotic and biotic variables in driving the production of multiple-stems in this genus,within a 25-hm~2experimental forest dynamics plot in Changbaishan(CBS)temperate forest.We used generalized linear mixed models to perform analyses at two levels(community-and specieslevel).We found seven Acer species in total within the plot,where they form a key part of the forest community.Our results show that abiotic factors play a more important role in producing multi-stemmed trees at the community level in CBS.At the species level,the relative importance of different factors varied among species.Shrub species tended to have a higher frequency of multi-stemmed trees under stressful conditions,whereas tree species tended to have more multi-stemmed trees in more suitable habitat.Our results indicate that the relative importance of different factors influencing the frequency of multi-stemmed individuals in Acer differs at the community and species level in the temperate forest.  相似文献   
76.
1Introduction TheThreeGorgesProject (TGP)ontheYangtzeRiverisoneofthegrandestwaterconservancyprojectsintheworld .Withadepthof 1 85meters,thereser voircanaccommodatewaterof39.3bil lioncubicmeters.Thepowergenerationcapacityis 1 8 2millionkilowatts.Whencompleted ,theprojectwillsup plyahugeamountofelectricityandhaveafunctionofservingthefloodcon trolpurpose,facilitatingshippingandadjustingthewaterfluxofthetrunksoftheYangtzeRiver.Itwillprovetobeahighlyefficientandcomprehensivehydraulicproject.A…  相似文献   
77.
This study predicts that quasi-periodic oscillations could exist in a detailed model of glycolysis that is analyzed in an autonomous system. In addition to period-doubling, quasi-periodic and period-adding bifurcation, a new stationary branch, which lies in between the thermodynamic and flow branches, is also uncovered in the glycolytic reaction system. Results presented in this study illustrate that the Michaelis constant (K4GAP) of glyceraldehyde 3-phosphate dehydrogenase for glyceraldehyde 3-phosphate has great influences on glycolytic oscillations, in which increasing K4GAP widens the range of flow rate over which quasi-periodic oscillations exist.  相似文献   
78.
0 IntroductionI soetes hypsophila, a Chinese endemic species, is a memberof the heterosporous aquatic quillworts, and is a perennialdistributed in shallow zones of plateau lake or plateau marsh ofSichuan and Yunnan Province in China. In recent years, I.hypsophilahas declined rapidly in population quantity (num ber) and has even disappeared from many locations. The spe cies is now considered to be rare and threatened or endangeredin China and is listed among first category of protected wil…  相似文献   
79.
Single-crystal X-ray diffraction structural data of four Fe-Mg tourmalines with different Fe contents from Xinjiang, Sichuan, and Yunnan Provinces, China, were collected at room temperature and ?100℃. The intrinsic dipole moments of polyhedra and the total intrinsic dipole moment of the unit cell were calculated. By comparing the intrinsic electric dipole moments of the X, Y, Z, T, and B site polyhedra, it is found that the T site polyhedron makes the greatest contribution to the total intrinsic dipole moment. The pyroelectric coefficients of four Fe-Mg tourmalines were experimentally determined, and the influence of intrinsic dipole moments on their pyroelectric properties was investigated. The experimental results show that, compared with the case at room temperature, the intrinsic dipole moments change with the total Fe content at ?100℃ in a completely different way. With the decrease of temperature, the total intrinsic dipole moments of tourmaline decrease. Over the same temperature interval, the pyroelectric coefficients increase with the increase in intrinsic dipole moment.  相似文献   
80.
Co68.15Fe4.35Si12.25B15.25 (at%) amorphous microwires with a smooth surface and a circular cross-section were fabricated by the glass-coated melt spinning method. Their mechanical properties were evaluated through tensile tests of the glass-coated amorphous microwires, and their fracture reliability was estimated using two- and three-parameter Weibull analysis. X-ray diffraction and transmission electron microscopy results showed that these glass-coated Co-based microwires were mostly amorphous. The coated Co-based microwires exhibit a tensile strength of 1145 to 2457 MPa, with a mean value of 1727 MPa and a variance of 445 MPa. Weibull statistical analysis showed that the tensile two-parameter Weibull modulus of the amorphous microwires is 4.16 and the three-parameter Weibull modulus is 1.61 with a threshold value as high as 942 MPa. These results indicate that the fabricated microwires exhibit good tensile properties and fracture reliability, and thus appear to be good candidates for electronics reliability engineering applications.  相似文献   
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