用磁场线圈产生磁屏蔽效果在氢钟上运用的可行性分析

随着中国航天技术的发展,对小型化的氢原子钟的需求越来越迫切。在减小体积和重量的前提下为保持氢钟现有的工作指标,对现有的氢钟物理条件提出了更高的要求,其中包括在氢钟屏蔽层数减少时保持磁屏蔽系数不变。原理分析、计算仿真了高磁导材料和磁场线圈2种屏蔽方法在氢钟上使用的优劣性,并通过对比实验验证了在氢钟上使用磁场线圈代替磁屏蔽材料产生磁屏蔽效果的可行性。     

Vertical migration of Daphnia galeata – Evidence for the use of an alternative resource from a lethal environment

Metazoans normally avoid anaerobic environments, at least when they are combined with toxic stress due to hydrogen sulfide. In Lake Speldrop, a small but deep gravel pit lake at the Lower Rhine, Daphnia galeata was found not only to dominate the zooplankton community, but was also regularly found in anoxic and even sulfidic layers during summer. We conducted field experiments with a newly developed “Zooplankton In-situ Incubator”, simulating vertical migrations of D. galeata. When daphnids were exposed to sulfidic conditions, mortality increased with exposure time, revealing LT₅₀-values between 129 and 42 min in relation to increasing concentrations of sulfide. Additionally, those experimental individuals originating from 12.5 m depth showed significantly higher mortality rates than those from 7.5 m depth. Further migration experiments showed that an interruption period of sulfidic exposition in less stressful environments reduced mortality rates significantly. Daphnids found in the hypolimnion belonged partly to moribund parts of the population; however, the majority of daphnids showed regular mowing activity and was able to withstand sulfidic conditions in the hypolimnion for a limited time. It is so far unclear what maybe the major ultimate factor for this type of short term migratory behavior, to seek for shelter or to use high amounts of sulfur bacteria as an alternative food resource.     

Physical-chemical and electrochemical characterization of Fe-exchanged natural zeolite applied for obtaining of hydrogen peroxide amperometric sensors

This work demonstrates that a Fe-exchanged zeolitic volcanic tuff from Cepari (Fe/CV) (Bistrita-Nasaud County, Romania) is suitable for the amperometric detection of H₂O₂, using new modified carbon paste electrodes based on this material (Fe/CV-CPEs). The physical-chemical characterization of natural (CV) and modified (Fe/CV) forms was realized using chemical analysis, optical microscopy, scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transformed infrared (FTIR) spectroscopy. The resulting electrodes (Fe/CV-CPEs) were investigated using cyclic voltammetry and chronoamperometry measurements. The new electrodes showed good electrocatalytic activity toward H₂O₂ reduction. The calibration curve for H₂O₂ determination was linear up to 0.1 mM, with a detection limit (signal to noise ratio of 3) of 20 μM.     

华北地台北缘东段金矿床氢氧同位素地球化学研究

华北地台北缘与金矿床有关的花岗岩类以贫D为特征,由其衍生的岩浆水δD=—120‰——85‰,δ~(18)O=5.0‰—8.0‰。H,O同位素研究表明,太古宙绿岩建造金矿床成矿流体为地壳深处多源混合水,以δD,δ~(18)O十分稳定为特征;显生宙花岗岩建造金矿床成矿流体为与金铜系列花岗岩再平衡的岩浆水;火山岩建造金矿床成矿流体为大气降水与岩浆水的混合产物,以δ~(18)O的明显漂移为特征;古生代绿岩建造金矿床的成矿流体为被花岗岩侵入体加热的大气降水,以δD特别低为特征。     

氢原子钟辅助电子学系统电路设计改进

氢原子钟辅助电子学系统已稳定工作多年,但是与目前的先进技术相比,原来的设计理念已显陈旧,同时暴露出外围电路庞杂、故障点比较多、问题查找困难等诸多问题;运用ARM+FPGA模式对电路进行了改进,其中运用12 bit高精度模数转换芯片实现参数采样,数字化设计改进氢原子钟智能温度控制系统,采用直接数字式频率合成器(Direct Digital Synthesizer,DDS)技术设计产生综合器频率信号,简化设计实现氢原子钟的通信功能;从测试结果来看,提高了参数的采样精度,数字化的智能温控模式实现了温度的自动化智能调整,直接式频率合成器技术简化了设计电路,基于i Coupler磁隔离技术的隔离型RS-232接口收发器设计提高了接口的稳定性;从整体设计来看,大大简化了设计电路,提高了系统性能及可靠性。     

Radial matrix elements of hydrogen atom and the correspondence principle

Radial dipole matrix elements having astrophysical importance have been computed for highly excited states of hydrogen atom. Computation is based on Heisenberg’s form of correspondence principle for Coulomb potential. Particular attention has been paid to the choice of classical analogue(n _c) of principal quantum number (n). The computed radial matrix elements are in good agreement with quantum mechanical results. Further, radial matrix elements for few transitions involving highn neighboring states of hydrogen atom are presented.     

Holocene records of carbon and hydrogen isotope ratios of organic matter in annually laminated sediments of Lake Korttajärvi, central Finland

An 11.6 m long continuous succession of annually laminated sediments from Lake Korttajärvi in central Finland was investigated for the isotopic composition of carbon and hydrogen in organic matter. The sequence covers a time period of 9590 years, and the varve chronology has been thoroughly described in earlier studies. From 7100 to 4400 BC the lake was part of the Ancient Lake Päijänne, but in 4400 BC it became separated and formed the present independent lake system. Two organic fractions were investigated. One fraction obtained by HCl-treatment was analyzed for δ¹³C and another HCl-HF-digested organic fraction was analyzed for both δ¹³C and δD. The isotopic data were compared to atomic C/N ratios, carbon contents, diatom-inferred pH values and other environmental parameters. The diatom-inferred pH values and organic carbon contents provide evidence for a long-term change towards more acidic conditions and lower productivity in Lake Korttajärvi. The inferred pH values decrease from 7.0 to 6.1, followed by a slight increase during the last millennia. Variations in pH are accompanied by an increase in the δ¹³C_HCl-HF values of organic matter from ?31.6 to $-29.2\permilleAn 11.6 m long continuous succession of annually laminated sediments from Lake Korttaj?rvi in central Finland was investigated for the isotopic composition of carbon and hydrogen in organic matter. The sequence covers a time period of 9590 years, and the varve chronology has been thoroughly described in earlier studies. From 7100 to 4400 BC the lake was part of the Ancient Lake P?ij?nne, but in 4400 BC it became separated and formed the present independent lake system. Two organic fractions were investigated. One fraction obtained by HCl-treatment was analyzed for δ¹³C and another HCl-HF-digested organic fraction was analyzed for both δ¹³C and δD. The isotopic data were compared to atomic C/N ratios, carbon contents, diatom-inferred pH values and other environmental parameters. The diatom-inferred pH values and organic carbon contents provide evidence for a long-term change towards more acidic conditions and lower productivity in Lake Korttaj?rvi. The inferred pH values decrease from 7.0 to 6.1, followed by a slight increase during the last millennia. Variations in pH are accompanied by an increase in the δ¹³C_HCl-HF values of organic matter from −31.6 to , followed by a subtle decrease to . The changes in pH and δ¹³C_HCl-HF are closely related (r = − 0.91, P < 0.01), and apparently reflect changing environmental conditions in the lake and in its catchment area. δD values show a marked shift to higher values during the early Holocene, which may be partly related to a climatic amelioration leading to the Holocene Climatic Optimum in 6000–2500 BC. The Medieval Warm Period in AD 980–1250 is associated with a local maximum in δD, lending support for a significant warming during that time.     

Surface and rheological properties of as-received colloidal goethite (α-FeOOH) suspensions: pH and polyethylenimine effects

The yield stress and zeta potential (ζ) of slurries prepared from as-received goethite were evaluated as a function of pH, solids concentration, cationic polyethylenimine (PEI) concentration and molecular weight (Mw). The goethite slurries displayed a maximum yield stress at the isoelectric point (pI). These slurries do not have a low pH dispersed region. The yield stress obeyed the yield stress–DLVO force model. The maximum yield stress displayed a dependence on the solids volume fraction to a power of 3.8.PEI adsorbed and changed both the surface chemistry and rheological yield stress of the slurries. At most additive concentration ranging from 0.1 to 0.4dwb% for PEI of Mw 600, 1800 and 70,000, the maximum yield stress of the slurries is larger than that with no adsorbed additives. At low PEI concentration of 0.1dwb%, the same maximum yield stress of 30 Pa was obtained for three Mws; 600, 1800 and 70,000 representing a 1.5-fold increase. The increased attraction between particles was attributed to charge patch attraction at low surface coverages and hydrogen bonding at high coverages. Adsorbed PEI decreased the yield stress at low pH. However complete dispersion was observed only for 0.4dwb% PEI with Mw 70,000, at pH below 7. Complete dispersion was not observed at high pH for the same polymer at all concentrations.     

论硫化氢生成的地质条件

根据硫化氢的赋存环境、组成特征和热还原反应模拟试验等,提出硫化氢生成需具备五项基本地质条件:(1)地层中富含石膏;(2)富含还原剂—烃类物质;(3)较大埋深或较高的地温条件;(4)地层水作为介质和反应场所;(5)严密的封存体系。热还原反应必须在有水条件下才能进行,硫酸盐水解后的硫酸根是硫化氢的直接供体。硫化氢的生成实际经历了一个天然气向地层水的溶入和脱出过程,两者的密切关系造成含硫化氢天然气通常出现在气-水界面附近,密封条件极好的岩性气藏或构造气藏当中,构造低部位或气藏下倾方向。但是,后期构造抬升有可能造成硫化氢与地层水的分离。     

A Pilot Study of Trophic Level and Human Origins at the Xiaoshuangqiao Site, China (ca. 1400 BC) Using δD Values of Collagen

We present here a pilot study to examine trophic level effects and migration patterns at the middle Shang Dynasty site of Xiaoshuangqiao in Henan Province using δD results combined with δ13C and δ15N values. A total of 33 specimens (17 humans, 7 cattle, 5 pigs, 3 sheep, 1 dog) of bone collagen were isotopically analyzed for δ13C, δ15N, and dD values. A strong positive correlation (R2 = 0.94) between mean δ15N and δD values of herbivores (cattle and sheep), omnivores (pig), carnivores (dog) and humans was observed. The δD results were found to increase by ~10‰ to 20‰ from herbivores to omnivores to carnivorous, evidence that collagen δD results are a useful indicator for the study of trophic levels and dietary patterns at archaeological sites. The δD results were also used to examine the origins of two different groups of individuals buried at Xiaoshuangqiao. Individuals buried in sacrificial pits of district V had mean δD values (?47.0 ± 2.9‰, n = 11) that were significantly (p = 0.049) elevated compared to the people buried in the stratigraphy of district IX (?51.3 ± 3.3‰, n = 3), indicating that they were ingesting water from different locations. In addition, the D values of the people buried in the stratigraphy were similar to the pigs (?54.5 ± 4.2‰, n = 5) at Xiaoshuangqiao, suggesting that they were most probably of the local population, and that the individuals buried in the sacrificial pits were most possibly from the coast and prisoners of the Dongyi (“东夷”) people. Thus, δD results have the potential to examine human origins and migration patterns and should be increasingly used in conjunction with δ13C and δ15N values at archaeological sites.