School of Teacher, Nanjing Xiao Zhuang University, Nanjing, 210000, China

Abstract

The nuclide 14 C can be produced in the atmosphere by high energy particles and γ-rays from high-energy phenomena. Through the carbon cycle, some of 14 CO 2 produced in the atmosphere can be retained in annual tree rings 1, 2 . Four events of rapid increase of the 14 C content occurred in AD 775, AD 994, BC 660 and BC 3371 were found 3-6 . Recently, the data of Jull et al. (2020) was inconsistent with our records around BC 3371. We measured our sample again and found the 14 C records are consistent with the value in Wang et al. (2017). Therefore, our 14 C records are robust. The inconsistency may be caused by the difference of calendar ages for the wood samples, or the physical origin of the event. First, crossdating on ring width can be performed only between trees whose growth has the same environmental conditions. Because the master tree-ring for dendrochronology is lack for Chinese trees. The master tree-ring from California has to be used. Therefore, the calendar ages derived from dendrochronology may be not precise. Second, the 14 C even may be not global. One evidence

Decreasing spatial variability of drought in southwest China during 1959–2013

“…As expected, the drought in SW China, regardless of its duration (DM), severity (DS) and the DA (percentage of the stations with PDSI < −2.0), increased in the past decades (Figures and ). The distribution and temporal patterns of DM 5 , DS 5 (Figure ) and the joint return period T (DM > 4, DS > 2) (Figures and (a)) indicated that central and northern Yunnan were facing high risks of severe droughts, and DS and risks significantly increased in SW China (Wang, ; Yin, ; Sun et al ., ). These results were a little different from those in Liu et al .…”

“…According to the historical records, there were 53 droughts hitting SW China from the year 1951 to 2011, and the average duration of these droughts were 116 days (Wang, ). On the other hand, in the PDSI DS categories, PDSI <−2 represents moderate drought (Mu et al ., ).…”

“…Southwest (SW) China is known for its susceptibility to recurring droughts. Historical records illustrated that 53 droughts occurred in SW China in the period of 1951–2011 (Wang, ). However, SW China is limited in its ability to mitigate and recover from natural hazards, due to its overpopulation, undeveloped economy and society, fragile ecosystem and the geological settings (Liu et al ., ).…”

Design and Analysis of the Elastic-Beam Delaying Mechanism in a Micro-Electro-Mechanical Systems Device

“…The traditional delaying mechanism mainly includes the non-returning clock mechanism, the gas or liquid damping mechanism, the quasi-fluid mechanism, and so on [1,2]. …”

Solvent‐Free Synthesis of Surfactants of High‐Carbon Alkyl Phosphates Used for Cosmetics

“…Until now, the preparation of alkyl phosphates has been mainly focused on low‐carbon alkyl phosphates (Clarke and Lyons, ; Davis, ; Du and Zhou, ; Hansell and Faulkner, ; He et al, ; Jiang, ; Lee, ; Li et al, ; Obata and Mukaiyama, ; Okabe et al, ; Okamato, ; Qiang et al, ; Ren et al, ; Thilo and Sauer, ; Wang, ; Wu et al, ; Xia et al, ; Ye and Yan, ), and little attention has been paid to the preparation of alkyl phosphates with alkyl chain length above 18, since the reactions between high‐carbon alcohols and phosphorylating reagents are difficult without solvents to obtain the high‐carbon alkyl phosphates. He et al () prepared octadecyl phosphates by means of removing water from azeotropic solvents, and Xu et al () adopted the method of adding solvent to synthesize the high‐carbon alkyl phosphates from C18 to C22.…”