Chemical and Isotope Investigations in Dissolved Gases of a Meromictic Residual Lake

Abstract

Lake Hufeisen near Halle/Saale has been formed in an old mining pit. Its deepest part is trench shaped and filled with water of sodium chloride content. Due to the density difference strong mixing processes in this part of the water body are prevented all over the year (meromictic lake). Therefore anoxic conditions have been established and the organic matter of the lake sediments is converted to carbon dioxide and methane. Over a period of more than one year gas samples were collected from different water depths. The investigations of the chemical composition (mainly nitrogen, carbon dioxide and methane) and the carbon isotope ratios show different relationships for individual species. The results are discussed with respect to the behaviour of the gases in the water column and to the stability of the density stratification in the saline bottom water.     

氩气中高次谐波辐射的研究

报道了在４５ｆｓ－２ＴＷ激光装置上以Ａｒ惰性气体为介质产生高次谐波的实验结果,实验中通过研究气体密度和激光能量对谐波辐射的影响,找到了适当的气体密度和激光能量范围,并在Ａｒ气中观察到８１次（９．７ｎｍ）的皆波辐射,这时迄今为止,人们在Ａｒ气中所能观测到的最短波长的谐波辐射,经分析表明,高于５７次的谐波是由Ａｒ离子产生的。     

Production and Applications of Spin-Polarized Isotopes of Noble Gases

The development of a new direction of research on the production and application of spin-polarized isotopes of noble gases, ³He and ¹²⁹Xe, is overviewed. Methods of laser hyperpolarization, problems of enhancing the efficiency of laser energy input, and methods of storing hyperpolarized (HP) isotopes are described. Examples and advantages of using HP isotopes in fundamental physics, engineering, medicine, and biology, as well as the progress in the creation of biosensors on hyperpolarized noble gases, are discussed. It has been shown that the study of protein structures and host–guest molecular complexes can prove useful in searching for means of the targeted delivery of radioactive isotopes (radiopharmaceuticals) in nuclear medicine. It is concluded that the progress in modern technologies for producing miniature electronic devices is suggestive of an imminent emergence of small-size scanners for human brain research. At the same time, a high sensitivity of the method is expected to provide the possibility of studying not only the structure of tissues and bloodstream, but also the response of the brain to various stimuli, and even cognitive functions.     

Electrical Conductivity of Noble Gases at High Pressures

We present experimental and theoretical results for the electrical conductivity of noble gases (He, Ne, Ar, Kr, Xe) up to high pressures where a transition from nonmetallic to metallic‐like conductivities occurs. In addition, we show the behavior of the thermal conductivity and thermopower for xenon as an example. The experiments were performed using explosively driven shock waves. Different geometries allow to probe various parameter regions up to several megabars. Besides single‐shock experiments along the principal Hugoniot curve, also multiple‐shock experiments were performed which follow almost an isentrope. The theoretical calculations were performed within a partially ionized plasma model. The composition is determined by solving a system of mass action laws. The transport coefficients are calculated within linear response theory taking into account the relevant scattering mechanisms of electrons at different ion species, atoms, and other electrons. The general trends of the experimental results can be explained within this theoretical approach. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Similarity Relations for Low Pressure Glow Discharges in Noble Gases

A simple three level atomic model that includes excitation, ionization, stepwise ionization, and diffusion is used to determine similarity relations for low pressure noble gas discharges. A two-temperature electron energy distribution is also included in the model. Similarity relations involving the reduced electric field, the electron main body temperature, the electron tail temperature, and the pressure-radius product are developed. It is found that the reduced electric field and the electron tail temperature depend on the discharge current as well as the pressure-radius product. Good agreement is obtained between the similarity relation predictions and experimental results in helium and neon discharges.     

惰性气体黏度的剩余熵标度模型

黏度是能源、动力、化工等系统设计分析中常用的重要物性参数.本文探讨了5种惰性气体(He、Ne、Ar、Kr、Xe)气相和超临界黏度的计算,以实际气体与同温度稀薄气体的黏度之比作为无量纲对比黏度,发现5种惰性气体的无量纲对比黏度与剩余熵之间满足同一单值函数关系,据此建立了惰性气体的气相和超临界黏度模型,其中稀薄气体黏度关联...     

Generation of K-Shell Radiation of Noble Gases in the Microsecond Implosion Regime

Russian Physics Journal - Studies of K-shell plasma radiation sources were performed on the GIT-12 generator (4.7 MA, 1.7 μs). In the experiments, a new type of load configuration was used to...     

The Theory of Ionization Waves in the Contracted Discharge of Noble Gases

Positive column plasma in noble gases at middle pressures is analysed for stability in the frames of the linear hydrodynamic theory. At critical values of pressure and current the discharge becomes unstable to radial contraction (contraction) and to wave disturbances of the type of current pinch constrictions (contraction ionization waves). Ionization waves in the contracted discharge are three-dimensional formations with electron concentration oscillations on the axis in the opposite phase with current pinch cross section. The discharge diffuse-recombination theory was used for analysing the problem of instability arising.     

Multiple M‐Effect Signal in Noble Gases and Hydrogen Mixture Discharge

The M‐effect (monochromatization‐effect) is a powerful process which can give high intensity monochromatic spectra with a certain wavelength depending on the type of used gas mixtures to generate the plasma state. The effect consists in the emission of a single spectral line emerging from plasma under specific experimental conditions involving one electropositive gas and one electronegative gas mixture. For example, in the case of Ne‐H₂ mixture, a clear monochrome radiation was obtained, corresponding to the λ_Ne =585.3 nm wavelength at 2p₁‐1s₂ transition in the Paschen notation, the pressures ranging between 10‐100 torr. In this paper we prove the general character of this effect, i.e. if the optical emission spectra (OES) reduced to selective lines can be noticed also in other multiple gas mixture discharges. The Ne‐Ar‐Xe mixture discharges with different percentages of H2 as electronegative gas added in has been investigated. The triple M‐effect, means three specific monochromatic lines, could be revealed in the OES at 50% of H2 addition in Ne‐Ar‐Xe mixture (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Free‐Electron Gas Spectrum Uniqueness in the Mixture of Noble Gases

Gas mixtures can reach the Maxwell's specter shape in case of low‐ionized mono‐atomic mixtures in the weak electric field. The parameters pertaining to the Maxwell spectrum of free electrons' gas straightforwardly settle on the insulating characteristics of the examined gas mixture at the fundamental level. In this paper, a condition for breakdown has been accomplished taking as a starting point the ionization coefficients derived accordingly, as well as the conditions for breakdown in keeping with the Townsend mechanism. The dc breakdown voltage value of noble gases mixture has been measured in the experimental part of the paper. The hypothesis that the free‐electron gas spectrum is unique in the noble gas mixture and is of Maxwell's type has been verified. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

An Experimental Study of Noble Gas Isotope Separation by DC ArcDischarge

Experiments are undertaken on the isotope separation by DC discharge through a narrow capillary of gaseous neon, argon and krypton of natural isotopic abundance. It is confirmed that the heavier isotopes become enriched in the region of cathode, and the lighter isotopes in that of anode. The effect on the obtainable separation factor brought by differences in experimental conditions is examined by changing the capillary tube diameter, tube length, discharge current and discharge pressure. The separation factor improves with increasing the tube length and the discharge current, and with decreasing the discharge pressure and the tube diameter. Ion density and electron temperature are measured in the positive column to compare the present experimental results with existing theories. The order of the isotope enrichment factor is well explained by the theory of the ion diffusive friction force onto isotopically different neutral molecules, together with the theory of the ionization degree of the different isotopic species.     

石盐中硼含量及其同位素的准确测定

基于Cs₂BO+₂的正热电离质谱法测定样品中硼同位素时,硼含量的准确测定直接制约着硼同位素测定的成败。目前,使用电感耦合等离子体原子发射光谱仪(ICP-OES)测定高盐样品的硼含量仍然存在很大问题,主要体现在两个方面： 高盐的基体干扰和仪器检出限制约,而仅仅依靠简单的稀释无法很好的解决这些困难。因此对样品进行硼元素的预富集以及基体离子的去除是十分必要的。在使用硼特效树脂进行硼元素的吸附时发现部分钠离子也会被同时吸附,故采用3 mol·L-1的氨水可以洗脱大部分吸附的钠离子而不造成硼的损失,达到了去除基体的目的。随后使用10 mL 75 ℃的0.1 mol·L-1盐酸将硼特效树脂吸附的硼洗脱实现了样品中硼的富集。ICP-OES测定硼含量时,选择波长为208.900 nm,样品的加标回收率在106.00%～108.40%之间,检出限为0.006 mg·L-1,定量下限为0.02 mg·L-1。通过不同盐度下的12次重复实验,其相对标准偏差小于5%,在1.94%～3.37%之间,因此该方法是可行的,并不存在偶然误差。联合此方法和Cs₂BO+₂离子的正热电离质谱法,成功测定了8个地质石盐样品的硼含量及硼同位素组成。     

Chemical-Shifts in Magnetic-Resonance of the 3He Nucleus in Liquid Solvents and Comparison with Other Noble Gases

Gas-to-solution solvent shifts of ³He dissolved in 17 pure liquids were measured. Two types of samples were used, under helium pressures of about 2 and 30 atm. No measurable pressure effect on the shift could be detected. The gas-to-solution shifts are dominated by the bulk susceptibility, for which correction was made. The resulting medium-shift range in our solvents is about 0.8 ppm. Hence ³He provides an excellent probe for the detection of minute local magnetic fields at the site of noble-gas atoms. For the first time shifts in liquid solvents for all four NMR-accessible noble-gas nuclei (³He, ²¹Ne, ⁸³Kr, and ¹²⁹Xe) can be compared. The medium shifts of ³He show a roughly linear correlation to medium shifts of ¹²⁹Xe, ⁸³Kr, and ²¹Ne in the same solvents. The corrected relative solvent shifts, that is, the solvent effects divided by σ_d, the diamagnetic shielding of the free atom, and by the number of nearest-neighbor solvent molecules, are approximately equal for all four noble gases.     

Methodological Study on AMS Measurement of U Isotope Ratios in Nanogram U Samples

The determination of uranium isotopic composition in trace samples is important in different fields. A new measurement method that uses an accelerator mass spectrometry （AMS） technique has been developed for the analysis of uranium isotopic ratios in ultra-trace uranium samples at the China Institute of Atomic Energy. As result, about 5-nanogram level uranium samples analyzed with AMS is achieved.     

A Calculation of the Electron Temperature of Complex Plasma of Noble Gases Mixture in CCRF Discharge

In this paper the results of studying of the electron temperature of buffer and complex plasmas in mixtures of noble gases (helium + argon) in capacitively coupled radiofrequency (CCRF) discharge are presented. The optical properties of dusty plasma in argon, helium and their mixtures have been studied using optical diagnostic methods. Based on spectral lines of plasma forming gases, the dependence of the electron temperature on gas pressure and discharge power has been determined. The axial distribution of electron temperature in the interelectrode gap has been measured. Measurements have been made using an RF compensated electric probe. The comparison of the experimental results shows that admixture of a small amount of argon to helium leads to a decrease in the electron temperature of buffer plasma. The presence of dust particles in the plasma causes an increase in the electron temperature. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

用模型势方法研究正电子与稀有气体的弹性散射

用模型势方法和STO波函数系统地计算了低能正电子与He, Ne, Ar, Kr, Xe和Rn惰性气体原子在非弹性阈值以下的散射角分布, 计算结果与已有的理论和实验数据吻合. 通过对算得的大量微分截面(散射角从20°到160°)的数据进行分析, 总结出了低能正电子与惰性气体原子弹性散射的规律.     

Development of Methods to Measure Carbon Isotope Ratios of Bacterial Biomarkers in the Environment

Abstract

The δ¹³C value of bacterial carbon is an important parameter in microbial ecology for studying the carbon flow within a microbial community and for the identification of ecological important strains involved in the mineralization of certain carbon pools in the environment. In our study, biomarkers were isolated from bacteria from a microbial consortium derived from two chemostats and δ¹³C values were measured. Similar isotope ratios between biomarkers such as fatty acids and outer membrane protein, biomass and substrate were observed. The δ¹³C analyses of outer membrane protein F of Pseudomonas and biomarker fatty acids were combined to follow bacterial assimilation of ¹³C labelled 4-chlorocatechol. This new approach was also used in the environment where soil samples were cultivated with different ¹³C traced substrates.

The isotopic analyses of bacterial biomarkers indicated that carbons of histidine were widely incorporated into bacterial biomarkers, in contrast to 4-chlorocatechol which was less often used as a substrate. Results indicate that by isolating bacterial biomarkers and measuring their δ¹³C values, activities of microbial communities in a complex environmental sample can be determined. This new method has the potential to elucidate individual carbon sources for individual bacterial taxa in microbial ecology.     

Simulation of Femtosecond Pulse Propagation through Hollow Fibre Filled with Noble Gases of Gradient Temperature

We propose a novel technique for generating intense few to mono-cycle femtosecond pulses. The simulation demonstrate that for the temperature difference of 300K, the spectrum of the output pulses is increased by 67% and the transform limited pulse width is reduced almost by half, compared with those obtained with hollow fibres in uniform temperature.     

Stable Isotope Ratios and Uric Acid Preservation in Termites Belonging to Three Feeding Habits in Thailand

Abstract

Nitrogen and carbon stable isotope ratios and uric acid concentrations in termites sampled from a dry evergreen forest in Thailand, were determined across three kinds of feeding habits. Feeding habits of Microcerotermes crassus, which is an abundant woodfeeder, and Dicuspiditermes makhamensis, a common soil-feeding termite, were confirmed by isotopic signatures. Lichen feeding termites (Hospitalitermes birmanicus, H. bicolor and H. ataramensis) were characterized by low δ¹⁵N values, suggesting that they assimilated nitrogen deposited from the atmosphere. There was also a significant difference in uric acid concentrations between termites representing different feeding habits. No significant relationships were found between uric acid concentrations and δ¹⁵N or δ¹³C in Hospitalitermes. However, δ¹⁵N values were correlated with C/N ratios in H. birmanicus, except in one colony of H. ataramensis. δ¹³C values in both species were negatively correlated with C/N ratios.