Back reaction and Hawking radiation from a Vaidya black hole

Using Damour-Ruffini’s and Hamilton-Jacobi’s methods, Hawking radiation from a Vaidya black hole is investigated. Due to non-stationary black holes, the event horizon r _H and the entropy S are all related to both the mass m(υ) and . When the back-reaction of particles’s energy to space-time is considered, we get the emission probability. It is found that the result is different from that of the stationary Schwarzschild black hole, because is the function of mass m(υ).      

Evaluating thermal history models for the Otway Basin, southeastern Australia, using (U-Th)/He and fission-track data from borehole apatites

New apatite helium and fission-track data from the Otway Basin are consistent with previously published borehole ages, confirming earlier suggestions that existing thermal models for basin evolution should be reevaluated. Analysis of the relationship between helium ages and grain size in newly analyzed samples, as well as in samples previously reported, reveals that grain size variations may contribute to the previously reported scatter in helium ages among aliquots of the same sample. In addition, systematic variations in apatite grain size with borehole depth or temperature may also have a significant effect on the interpretation of borehole helium age data. Incorporation of the observed grain size variations in Otway borehole apatites into forward models based on published thermal histories, principally based on vitrinite reflectance and fission-track data, suggests that existing models for the eastern Otway Basin are broadly consistent with the helium data. In contrast, thermal histories for western basin boreholes, now thought to be at maximum temperatures, predict helium ages that are generally older than the observed ages, implying that basin temperatures were hotter than indicated by the models. This discrepancy is consistent with a Cenozoic heating event in parts of the western Otway Basin similar to that documented for the eastern basin. The relatively wide spread of apparent apatite fission-track (AFT) ages and compositions compared to the restricted age range of helium measurements on coexisting grains, although not conclusive, supports previous suggestions that composition does not appear to affect the sensitivity of the He closure temperature in apatite.     

从He同位素组成探讨塔里木盆地与东部诸含油气盆地天然气的成气机制

通过天然气中He同位素组成来研究天然气的成气机制。用VG-5400静态真空质谱计测定了采自塔里木盆地古生代和中生代地层中天然气的He同位素,其He/4He=2.58×10-8～8.33×10-8,R/Ra=0.019～0.059Ra,平3均值为0.031Ra,而我国东部几个主要含油气盆地天然气的R/Ra平均比值则变化于1.21～2.30Ra。He同位素组成对比研究表明,东部含油气盆地成烃作用是在幔源热流驱动下热水流体与烃源岩水岩反应形成的,而塔里木盆地成烃热源则主要是盆地地热增温热水流体与烃源岩水岩反应形成的。     

氡、氦等气体地球化学在地震科学研究中的进展

系统回顾了氡、氦的气体地球化学特征及其在地震科学研究中的应用情况。在分析氡、氦等地下气体在地壳中浓度变化的影响因素基础上,总结出氡、氦等地下气体浓度变化具年变（或日变）规律,且受多种因素诸如其自身的地球化学行为、气候条件、地质构造及区域应力场等的综合影响。归纳了近30年来在氡、氦的理论和实验研究以及氡异常的形成机理研究方面所取得的进展。氡、氦等地下气体在地震监测预报及基础研究方面日益发挥出越来越重要的作用,但对其自身的认识还远远不够,提出了今后应在氡、氦等地下气体的异常迁移、实验研究、资料处理过程中对干扰因素的排除以及开展深部气体运移与地震活动的关系等方面开展研究的建议。     

Prediction of central California earthquakes from soil-gas helium fluctuations

The observations of short-term decreases in helium soil-gas concentrations along the San Andreas Fault in central California have been correlated with subsequent earthquake activity. The area of study is elliptical in shape with radii approximately 160×80 km, centered near San Benito, and with the major axis parallel to the Fault. For 83 percent of theM>4 earthquakes in this area a helium decrease preceded seismic activity by 1.5 to 6.5 weeks. There were several earthquakes without a decrease and several decreases without a corresponding earthquake. Owing to complex and unresolved interaction of many geophysical and geochemical parameters, no suitable model is yet developed to explain the observations.     

Measurements of the helium 584 Å airglow during the Cassini flyby of Venus

The helium resonance line at 584 Å has been observed with the UltraViolet Imaging Spectrograph (UVIS) Extreme Ultraviolet channel during the flyby of Venus by Cassini at a period of high solar activity. The brightness was measured along the disk from the morning terminator up to the bright limb near local noon. The mean disk intensity was ∼320 R, reaching ∼700 R at the bright limb. These values are slightly higher than those determined from previous observations. The sensitivity of the 584 Å intensity to the helium abundance is analyzed using recent cross-sections and solar irradiance measurements at 584 Å. The intensity distribution along the UVIS footprint on the disk is best reproduced using the EUVAC solar flux model and the helium density distribution from the VTS3 empirical model. It corresponds to a helium density of 8×10⁶ cm⁻³ at the level of where the CO₂ is 2×10¹⁰ cm⁻³.     

Characteristics of helium accumulation in the Guanzhong Basin,China

Guanzhong Basin is located in the transitional zone between the Qinling orogenic belt and the Ordos plateau. Analyses of drill and geothermal wells depict that the Guanzhong Basin has abundant gas, and its major source rocks are the U-rich granites. In this study, the granitoid intrusive samples were collected from the Huashan, Baoji, Muhuguan rocks in Guanzhong Basin. A micro laser Raman spectrum examination was used to measure the composition of inclusion in the granite quartz fissures. The results depict that the inclusions include both gas-liquid and H₂O-NaCl-CO₂ inclusions and that their composition primarily includes H₂O and CO₂, with small amounts of CH₄, H₂ and H₂S. These inclusions can be classified into nearly-primary, early secondary, and late secondary inclusions, which have homogenization temperatures of greater than 430 °C, 330–370 °C and 170–230 °C, respectively, based on the inclusion measurements. Additionally, the apatite fission-track investigations of six samples, which were collected from the granites at Huashan, Baoji rocks and the southern margin of Muhuguan along with the Cretaceous Sigou Formation sandstones that are located in the northwestern margin of the Guanzhong Basin reveal that the northern Guanzhong Basin began to receive deposits as early as 84–69 Ma. This period was accompanied by the rapid uplift of the Qinling orogenic belt, which was followed by an uplift of the southern basin margin and the Qinling orogenic belt from 44–28 Ma. The authors obtained an age histogram and a probability density distribution of three sample points. The results show that the age spectra of the zircons in the Cretaceous Sigou Formation sandstones can be divided into four tectonic events. Combined with the ages of apatite fission tracks and zircon, the Guanzhong Basin has experienced five tectonic stages as follows: 28–84 Ma, 170–260 Ma, 280–510 Ma, 610–1200 Ma, and 1210–2870 Ma. Using the thermal chronology constraints, inclusion composition analyses, which include the homogenization temperature measurements, and regional burial history, this paper conclude that the early secondary inclusions are primarily composed of CO₂ and N₂, whereas the late secondary inclusions are composed of CH₄. Furthermore, this paper identify two periods of reservoir accumulation, out of which the later period is assumed to be the main accumulation period. Therefore, the period of the formation of the late secondary inclusion in the Guanzhong Basin and the Miocene era is observed to overlap with the main helium reservoir accumulation period.© 2019 China Geology Editorial Office.     

A statistical adjustment of Haldorsen's conditioned Boolean simulation algorithm

This paper presents a new simulation algorithm for generating realizations of a Boolean model for sandstone reservoirs conditional on sandstone body intersections in wells. It is a statistically corrected version of the conditional simulation algorithm originally proposed by Haldorsen. In previous work it was shown that the conventional algorithm does not reproduce the correct statistics for sandstone body size at the well locations. The simulation of a Boolean model, given grain intersections on line transects, must be in accordance with the conditional distribution of the model, which implies that sandstone bodies intersected by wells and sandstone bodies in the interwell area should be simulated independently. Based on the conditional distribution a simulation algorithm is developed, which is compared to Haldorsen's algorithm by simulating an outcrop section of fluvial sandstone deposits. Simulations are conditioned on data of two fictitious wells. It turns out that the adjusted algorithm gives better results for the sand fraction that is connected to a set of wells, and also for the sand fraction that would be connected to an infill well.     

The diverse and contested meanings of sustainable development

We provide a heuristic framework that can be used as a lens for understanding the arguments being presented in the papers which comprise this special issue on sustainable development and environmental issues in Great Britain. This framework can also be used as an introduction to the wider literature on sustainable development because it is designed to bring greater clarity to this large, diverse and rapidly expanding field of enquiry populated by heterogeneous discourses, multiple approaches and a variety of recommendations as to the ways forward.     

北京丰台大灰厂井氦气释放特征探讨

结合观测环境条件,温度、大气降水等影响因素及强震响应,研究了大灰厂井氦气释放成因.结果显示,氦气释放与特殊的地质环境、温度有关,与大气降水无明显关系.