Further support for a Cretaceous age for the feathered-dinosaur beds of Liaoning,China:New 40Ar/39Ar dating of the Yixian and Tuchengzi Formations

We report new 40Ar/39Ar dating results obtained from total fusion and incremental-heating analyses of sanidine and biotite from three tuffs found interbedded within the fossil-bearing deposits of Liaoning, northeast China. The first is a new sample of the Bed 6 Sihetun tuff from the Yixian Formation, previously dated by our team as middle Early Cretaceous, and recently considered by Lo et al., partially reset due to metamorphism from a nearby basaltic sill. The second is the Yixian Bed 9 tuff from Hengdaozi considered by Lo et al. to be unaffected by metamorphism and whose age, based on total fusion 40Ar/39Ar dating of biotite, argues for a Jurassic age for the Yixian Formation.The third tuff is a previously undated tuff from the upper part of the underlying Tuchengzi Formation. Single crystal total fusion 40Ar/39Ar analyses of the Sihetun sanidine showed homogeneous radiogenic Ar, Ca/K ratios, excellent reproducibility and gave a mean age of 125.0 ± 0.18 (1SD) ±0.04 (SE) Ma. Single sanidine crystal total fusion 40Ar/39Aranalyses of the Hengdaozi tuff gave a mean age of 125.0 +0.19 (1SD) ± 0.04 (SE) Ma, which is indistinguishable from the Sihetun tuff. The Tuchengzi Formation tuff gave a mean age of 139.4 ± 0.19 (1SD) ± 0.05 (SE) Ma. Detailed laser incremental-heating analyses of biotite from Sihetun, Hengdaozi, and Tuchengzi tuffs show disturbed Ar release patterns and evidence of trapped argon components. We conclude from these analyses that the total fusion dates on biotite by Lo et al. are erroneously old and isotopic dating of both biotite and sanidine from tuffs of the Yixian Formation point to a middle Early Cretaceous age. The upper part of the Tuchengzi Formation can be referred to the Early Cretaceous.``     

长短桩复合地基荷载分担比的试验研究

为了研究长短桩复合地基竖向荷载分担比的变化规律,在室内模型试验的基础上,对不同桩间距、垫层厚度、长桩长度、短桩长度、长桩模量和短桩模量等情况下长短桩复合地基荷载分担比的变化性状进行了分析。结果表明,随桩间距的减小,长桩和短桩的荷载分担比均增大,桩间土的荷载分担比减小,通过减小桩间距来提高长桩荷载分担比是不经济的;随垫层厚度的增加,长桩的荷载分担比减小,桩间土的荷载分担比增大,短桩的荷载分担比变化较小,垫层的设置能明显改善桩、土荷载分担的分配;随长桩长度的增加,长桩的荷载分担比增大,桩间土的荷载分担比减小,短桩的荷载分担比变化较小,增加长桩长度能一定程度提高长桩荷载分担比;短桩长度对荷载分担比的影响较小;随长桩模量的增大,长桩的荷载分担比增大,桩间土的荷载分担比减小,短桩的荷载分担比变化较小,增加长桩模量能显著提高长桩荷载分担比;随短桩模量的增大,长桩的荷载分担比减小,短桩和桩间土荷载分担比均增大,增加短桩模量对荷载分担比分配有一定影响。     

能源利用浅述

能源的概念并不是一成不变的.随着人类科技的进步,一些未被人类认知的资源正渐渐揭开面纱,伴随着资源利用的各种技术也被开发.在未来社会,能源的种类及利用将多元化,这些都将推动社会的可持续发展.     

樟子松人工林细根生产、周转和碳归还对施氮的响应

在河北塞罕坝樟子松林, 设置对照样方、低氮(20 kgN/(hm²·a))、中氮(50 kgN/(hm²·a))和高氮(100 kgN/(hm²·a))添加4种处理, 分0~10, 10~20和20~30 cm共3个土层, 系统地研究细根生产、周转、碳归还以及细根生产力(NPPfr)占生态系统净初级生产力(NPP)的比例对不同程度氮可获得性的响应, 结论如下: 1) 细根生产力在低氮下增大, 高氮下降低; 细根生产力占NPP的比例则相反, 在低氮下降低, 中氮下升高; 2) 随氮浓度增大, 细根生物量逐渐降低, 细根周转率增大, 细根碳归还先升(低、中氮)后降(高氮); 3) 施氮对细根生产力的影响随土壤深度的加深无显著变化, 施氮对细根周转率的影响在不同深度间则差异显著; 4) 结构方程模型表明, 氮添加通过对土壤碳氮含量、pH的影响而改变细根生产力, 通过对细根碳氮含量的影响改变细根周转率。     

Further support for a Cretaceous age for the feathered-dinosaur beds of Liaoning,China:New 40Ar÷39Ar dating of the Yixian and Tuchengzi Formations

We report new ⁴⁰Ar÷³⁹Ar dating results obtained from total fusion and incremental-heating analyses of sanidine and biotite from three tuffs found interbedded within the fossil-bearing deposits of Liaoning, northeast China. The first is a new sample of the Bed 6 Sihetun tuff from the Yixian Formation, previously dated by our team as middle Early Cretaceous, and recently considered by Lo et al., partially reset due to metamorphism from a nearby basaltic sill. The second is the Yixian Bed 9 tuff from Hengdaozi considered by Lo et al. to be unaffected by metamorphism and whose age, based on total fusion ⁴⁰Ar÷³⁹Ar dating of biotite, argues for a Jurassic age for the Yixian Formation. The third tuff is a previously undated tuff from the upper part of the underlying Tuchengzi Formation. Single crystal total fusion ⁴⁰Ar÷³⁹Ar analyses of the Sihetun sanidine showed homogeneous radiogenic Ar, Ca÷K ratios, excellent reproducibility and gave a mean age of 125.0±0.18 (1SD)±0.04 (SE) Ma. Single sanidine crystal total fusion ⁴⁰Ar÷³⁹Ar analyses of the Hengdaozi tuff gave a mean age of 125.0±0.19 (1SD)±0.04 (SE) Ma, which is indistinguishable from the Sihetun tuff. The Tuchengzi Formation tuff gave a mean age of 139.4±0.19 (1SD)±0.05 (SE) Ma. Detailed laser incremental-heating analyses of biotite from Sihetun, Hengdaozi, and Tuchengzi tuffs show disturbed Ar release patterns and evidence of trapped argon components. We conclude from these analyses that the total fusion dates on biotite by Lo et al. are erroneously old and isotopic dating of both biotite and sanidine from tuffs of the Yixian Formation point to a middle Early Cretaceous age. The upper part of the Tuchengzi Formation can be referred to the Early Cretaceous.     

规则表面形貌的表征

量子点与超晶格等有序结构呈现规则的表面形貌,它们的特性与表征表面粗糙度的参数密切相关.本文说明了如何利用单值周期函数对这些规则表面形貌进行模拟,并分析了其高度分布函数,以及给出了高度分布函数与单值函数导数变化的关系.     

公益征收补偿法理基础探讨

公益征收补偿的法理基础,经历了一个漫长的讨论和论证过程,无论国外还是国内,诸多学者都试图建立起自己的理论蓝图,来解释公益征收补偿的合理性。公共负担平等说、特别牺牲说、不当得利说等,都从不同视角对征收补偿进行了阐释,也取得了不同范围内的认同。但是以上学说似乎都未能摆脱法学理论范畴的局限,引入经济学上的公共选择理论,可以从一个全新的视角来审视公益征收补偿法理基础。     

小鼠胚胎干细胞对病毒性心肌炎的影响

目的使用小鼠验证这样一个假设:外界病毒浸入诱发心肌炎时,机体的干细胞将进入心脏提高心肌的抗病毒能力。方法雄性BALB/c小鼠分为三组:小鼠胚胎干细胞对照组(ES),心肌炎病毒组(EM CV)及EM-CV加ES治疗组。通过尾静脉注射,令小鼠立即感染病毒。小鼠死亡率,炎性细胞浸润及心肌坏死等为观察指征。干细胞的游走及分化等通过免疫荧光法来验证。结果给予干细胞后的小鼠的存活率明显高于生理盐水对照组,炎性细胞侵润及心肌坏死亦明显低于生理盐水对照组。免疫荧光法表明,干细胞进入心肌并分化成新的心肌细胞。结论干细胞能明显提高心肌炎小鼠的存活率,减少心肌组织的坏死。同时,亦证明当心脏遭受病毒的侵入后,干细胞通过某种机理修复或再生心肌细胞,从而提高组织的抗病毒能力。     

面向跨架构恶意软件的函数相似性检测和衍变分析

自动化的恶意软件衍变分析已成为当前一项重要的网络安全研究工作。函数相似性检测在软件衍变分析过程中扮演着关键角色,但是大多数现有的方法难以有效处理跨架构的情况。随着越来越多跨架构恶意软件的出现,如何在代码跨架构情况下准确地进行函数相似性检测以及衍变分析变得更加紧迫。为此,提出了一种新的基于Weisfeiler-Lehman图同构测试的函数哈希方法WLHash,从而能够高效地进行跨架构软件之间的函数相似性检测和衍变分析。实验结果表明,所提方法能够较为准确且高效地检测跨架构软件之间的函数相似性,并进而获取它们之间的衍变关系,同时计算开销比较低,适用于大规模的跨架构恶意软件衍变分析。