First Report of Avian Tracks from the Cretaceous of Tibet, China

<正>Objective Despite a large number of bird fossils in the Jehol Biota,Mesozoic bird records from other parts of China are dominated by tracks.Late Cretaceous bird tracks are rarely found in China.Reliable reports so far include a Dongyangornipes and Koreanaornis assemblage of early Late Cretaceous age from Dongyang City,Zhejiang Province,China(Azuma et al.,2013).Buckley et al.     

气候变化对拉萨河谷冬小麦主要生育期的影响分析

了解气候变化对冬小麦生育期的影响,可为农业应对气候变化、调整农作物种植结构提供科学依据。本文利用1996—2022年近26 a拉萨冬小麦生育期以及逐日平均气温（T_m）、最高气温（T_max）、最低气温（T_min）、气温日较差（DTR）、相对湿度（RH）、降水量（Pr）、日照时数（S）和≥0 ℃积温（∑T₀）等资料,采用线性倾向估计、Pearson相关系数和优势分析方法等,分析了拉萨河谷冬小麦生育期变化特征以及影响的主导气象因子。结果表明：(1)近26 a拉萨河谷冬小麦营养生长期（Vegetative Growth Period,VGP）、生殖生长期（Reproductive Growth Period,RGP）和全生育期（Whole Growth Period,WGP）的T_m均呈上升趋势,T_min升温率大于T_max的升温率,DTR、RH呈减小趋势,∑T₀、Pr和S趋于增加。(2)冬小麦拔节前各生育期提早,提早率为0.47~6.75 d/10 a;拔节后各生育期推迟,推迟率为3.17~7.03 d/10 a;VGP、WGP延长,RGP缩短。(3)拉萨河谷10月、1月T_min和2月T_m的升高,是冬小麦出苗、分蘖和返青期提前的主要因素,导致冬小麦拔节后生育期推迟的重要因素则是4—5月S增加及6月RH减少。     

Pyroxene mineralogies of near‐Earth vestoids

Abstract— We have calculated pyroxene mineralogies of seven near‐Earth asteroids (NEAs) with reflectance spectra similar to HEDs (howardites, eucrites, and diogenites). Two different sets of formulas (Gaffey et al. 2002; Burbine et al. 2007) are used to calculate the pyroxene mineralogies of the NEAs from their Band I and II centers. The band centers have been adjusted to compensate for the low temperatures on the asteroid surfaces. All of the derived mineralogies from the Gaffey et al. (2002) formulas and the Burbine et al. (2007) formulas overlap. The derived wollastonite (Wo) contents are very similar with differences being only approximately 1 mol%. The derived ferrosilite (Fs) contents differ by only 3 to 8 mol%. The determined pyroxene mineralogies for all seven near‐Earth vestoids are consistent with eucrites or howardites. None of the objects have pyroxene mineralogies consistent with diogenites. The absence of near‐Earth vestoids with pyroxene mineralogies similar to diogenites may indicate that it is difficult to produce sizeable (km‐sized or larger) bodies that are predominantly composed of diogenitic material, suggesting these objects are rubble piles of mixed ejecta.     

1981—2022年藏东南4种界限温度时空变化

基于1981—2022年藏东南（林芝市）4个气象站点的日平均气温数据,采用线性倾向估计、Person系数、Mann-Kendall检验、优势主导分析等方法,分析了藏东南≥0 ℃、≥5 ℃、≥10 ℃和≥15 ℃共4种界限温度的时空变化特征。结果表明：(1)受海拔影响,藏东南4种积温总体呈自东南向西北递减的变化特征,各地≥0 ℃、≥5 ℃、≥10 ℃和≥15 ℃积温分别介于3161.4~4429.9 ℃·d、2869.2~4018.0 ℃·d、2273.3~3258.0 ℃·d和608.8~2133.2 ℃·d。(2)近42 a藏东南4种界限温度均呈初日提前、终日推迟、持续日数延长的趋势,≥10 ℃界限温度变幅最小,除初日外,≥15 ℃界限温度变幅最大。≥0 ℃和≥5 ℃持续日数的延长主要是初日提前引起的,≥10 ℃与≥15 ℃持续日数的增加主要是终日推迟导致的。4种积温均表现出极显著的增加趋势,增幅分别为123.81 ℃·d/10 a、136.71 ℃·d/10 a、76.22 ℃·d/10 a、166.43 ℃·d/10 a。(3)年代际变化上,4种积温具有明显的逐年代际增加态势。21世纪10年代是研究时段内最温暖的10 a,这一时期的4种积温比20世纪80年代增加了174.9~437.2 ℃·d,其中≥15 ℃积温增幅最大。除≥10 ℃外,20世纪80—90年代初日推迟、终日提早、持续日数缩短,而21世纪前20 a则截然相反。(4)M-K检验显示,≥10 ℃初日、终日未发生气候突变,其他界限温度指标发生突变时间多在2004年前后。