Generalized Averaging Principle and the Secular Evolution of Planet Crossing Orbits

Planet crossing orbits give rise to mathematical singularities that make it not possible to apply the classical averaging principle to study the qualitative evolution of Near Earth Asteroids (NEAs). Recently this principle has been generalized to deal with crossings in a mathematical model with the planets on circular coplanar orbits. More accuracy is needed to compute the averaged evolution of planet crossing orbits for different purposes: computing reliable crossing times for the averaged motion, writing more precise proper elements and frequencies for NEAs, etc. In this paper we present the generalization of the averaging principle using a model where the eccentricity and the inclination of the planets are taken into account.     

Interferometric space missions for the search for terrestrial exoplanets: Requirements on the rejection ratio

The requirements on space missions designed to study Terrestrial exoplanets are discussed. We then investigate whether the design of such a mission, specifically the Darwin nulling interferometer, can be carried out in a simplified scenario. The key element here is accepting somewhat higher levels of stellar leakage. We establish detailed requirements resulting from the scientific rationale for the mission, and calculate detailed parameters for the stellar suppression required to achieve those requirements. We do this utilizing the Darwin input catalogue. The dominating noise source for most targets in this sample is essentially constant for all targets, while the leakage diminishes with the square of the distance. This means that the stellar leakage has an effect on the integration time only for the nearby stars, while for the more distant targets its influence decreases significantly. We assess the impact of different array configurations and nulling profiles and identify the stars for which the detection efficiency can be maximized.     

基于瓦斯抽采穿层钻孔的瓦斯地质勘查研究

针对回采工作面煤与瓦斯突出事故多发于煤厚变化带和隐伏小构造附近,研究了利用大量瓦斯抽采钻孔探明工作面瓦斯地质信息的技术途径。结合试验煤层工作面抽采钻孔施工设计,对抽采钻孔信息进行处理、建立数学模型,利用计算机作图软件对煤层厚度变化规律、隐伏小断层立体呈现,从而达到利用穿层抽采钻孔探明工作面前方隐伏瓦斯地质信息的目的。试验结果表明,工作面煤厚变化部位、遭遇断层位置与预测结果基本一致,回采阶段未出现瓦斯异常情况。     

熔融制样-波长色散X射线荧光光谱法测定铁矿石中主次量组分

建立了采用波长色散X射线荧光光谱法测定铁矿石中TFe、SiO2、AI2O3、MgO、CaO、K2O、Na2O、TiO2、MnO、P、S和Cu等12种主次量组分的分析方法。采用LiBO2-Li2B4O7混合熔剂熔融制样,以铁矿石一级国家标准物质为校准样品,通过加入Co2O3内标、使用理论α系数法和经验系数相结合的方法校正基体效应和谱线重叠干扰。方法的准确度、精密度达到了传统化学分析方法的要求,分析时间大大缩短,具有很好的使用价值。     

http://dx.doi.org/10.1016/j.gsf.2016.10.005

The Earth was born as a dry planet without atmosphere and ocean components at 4.56 Ga, with subsequent secondary accretion of bio-elements, such as carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) which peaked at 4.37–4.20 Ga. This two-step formation model of the Earth we refer to as the advent of bio-elements model (ABEL Model) and the event of the advent of bio-elements (water component) as ABEL Bombardment. It is clear that the solid Earth originated from enstatite chondrite-like dry material based on the similarity in oxygen isotopic composition and among other isotopes. On the other hand, Earth's water derives primarily from carbonaceous chondrite material based on the hydrogen isotopic ratio. We present our ABEL model to explain this enigma between solid Earth and water, as well as secondary accretion of oxidizing bio-elements, which became a precursor to initiate metabolism to emerge life on a highly reductive planet. If ABEL Bombardment had not occurred, life never would have emerged on the Earth. Therefore, ABEL Bombardment is one of the most important events for this planet to evolve into a habitable planet. The chronology of ABEL Bombardment is informed through previous researches of the late heavy bombardment and the late veneer model. ABEL Bombardment is considered to have occurred during 4.37–4.20 Ga, which is the concept to redefine the standard late heavy bombardment and the late veneer models. Also, ABEL Bombardment is the trigger of the transition from stagnant lid tectonics to plate tectonics on this planet because of the injection of volatiles into the initial dry Earth.     

EURONEAR: First results

The European Near Earth Asteroid Research (EURONEAR) is a project which envisions to build a coordinated network which will follow-up and recover potentially hazardous asteroids (PHAs) and near earth asteroids (NEAs). We aim to include in EURONEAR two automated 1 m telescopes located in Chile and Europe, in addition to other non-permanent facilities. Astrometry will be the main aim of the project in order to secure and follow-up newly discovered NEAs, also to recover PHAs at their second or following oppositions, while photometry of bright PHAs will bring information on their physical properties. In this paper, first we review briefly the existent and past NEAs programs. Next, we include the results obtained in 2006 from three observing runs at Pic du Midi using the 1 m telescope, Haute-Provence employing the 1.2 m telescope, and Bucharest using a small 23 cm telescope. These add a total of 153 positions for 16 PHAs and NEAs, which were accepted by Minor Planet Center. Recently, a 1 m telescope was allocated by ESO in La Silla to be automated and used as the Southern dedicated facility by EURONEAR.     

地幔矿物中CO2流体包裹体的微量元素特征

本文在镜下观测基础上，挑选富含CO2包裹体的地幔橄榄岩的橄榄石、斜方辉石和单斜辉石样品，运用热爆法提取和ICP—MS技术，直接测定了单矿物中CO2流体包裹体的稀土和微量元素含量。在同样条件下，采用四极质谱法测定了CO2等气相成分，并以CO2含量为参考值，得出流体中的微量元素相对含量。热爆样品的显微镜观测表明，靠近颗粒表面的较大的CO2包裹体在1000℃爆裂时均已破裂，所测定的REE和其他微量元素主要来自CO2包裹体。CO2流体／球粒陨石标准化的REE数据表明，地幔CO2流体相对于地幔岩或地幔矿物而言，富集稀土元素，特别是轻稀土元素，LREE／HREE为1．53～11．96，REE分馏程度较大，(La／Yb)N一般大于1。CO2流体／上地幔岩石标准化值研究表明，除Co、Ni外，铁族元素在地幔流体中趋于贫化；Cu、Mo、W、Bi、Ag等热液矿床的重金属成矿元素在地幔CO2流体中富集。     

Astrometry of near-earth objects using small telescopes

Currently, when a near-Earth object (NEO: any asteroid or comet approaching the terrestrial orbit about the Sun) is discovered, there is a distinct chance that it will be lost again due to the lack of suitable follow-up astrometry. The burgeoning international Spaceguard program — which has an aim of discovering and determining the orbits of all possible Earth-impactors so that calamitous collisions can be avoided-will make this problem more acute, as the discovery rate increases. When NEOs reach visual magnitudes brighter than 21, they may be observed with suitable CCD-equipped telescopes with apertures of one metre or less; in fact, even 0.25-m aperture instruments are now being employed to great effect in this regard. This means that in the present situation, countries or individuals having access to quite modest-sized and modest-priced equipment can make a real, valuable contribution to this international effort. When Spaceguard begins in earnest it will be vital that astronomers spread around the world, using small telescopes, take over the tracking of NEOs discovered by the large, expensive, search instruments. The Spaceguard project therefore represents an excellent opportunity for international collaboration, with scientists in developing nations being valuable contributors in a space program with real significance for all humankind. Presented at the UN/ESA Workshop on Basic Space Science: From Small Telescope to Space Mission, Colombo, Sri Lanka, 11–14 January 1996.

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由恐龙化石论晚白垩世事件沉积

本文根据晚白垩世恐龙化石的分布结合地层学特征,初步提出了这套含有恐龙化石的晚白垩世地层属于事件沉积的观点,并认为导致这次事件沉积的原因可能是由天体撞击地球产生的强海啸形成。     

CCD photometry of 23 minor planets

We present CCD photometric observations of 23 main-belt asteroids, of which 8 have never been observed before; thus, the data of these objects are the first in the literature. The majority showed well-detectable light variations, exceeding 0^m1. We have determined synodic periods for 756 Lilliana (936), 1270 Datura (34), 1400 Tirela (1336), 1503 Kuopio (998), 3682 Welther (359), 7505 Furushu (414) and 11436 1969 QR (123), while uncertain period estimates were possible for 469 Argentina (123), 546 Herodias (104) and 1026 Ingrid (53). The shape of the lightcurves of 3682 Welther changed on a short time-scale and showed dimmings that might be attributed to eclipses in a binary system. For the remaining objects, only lower limits of the periods and amplitudes were concluded.