A Mercury orientation model including non-zero obliquity and librations

Planetary orientation models describe the orientation of the spin axis and prime meridian of planets in inertial space as a function of time. The models are required for the planning and execution of Earth-based or space-based observational work, e.g. to compute viewing geometries and to tie observations to planetary coordinate systems. The current orientation model for Mercury is inadequate because it uses an obsolete spin orientation, neglects oscillations in the spin rate called longitude librations, and relies on a prime meridian that no longer reflects its intended dynamical significance. These effects result in positional errors on the surface of ~1.5 km in latitude and up to several km in longitude, about two orders of magnitude larger than the finest image resolution currently attainable. Here we present an updated orientation model which incorporates modern values of the spin orientation, includes a formulation for longitude librations, and restores the dynamical significance to the prime meridian. We also use modern values of the orbit normal, spin axis orientation, and precession rates to quantify an important relationship between the obliquity and moment of inertia differences.     

气相色谱-质谱法同时测定河流沉积物中多环芳烃和有机氯农药

建立了用加速溶剂萃取,气相色谱-质谱法同时测定河流沉积物中16种多环芳烃和19种有机氯农药的分析方法,优化了萃取溶剂、萃取温度和时间、凝胶渗透色谱收集时间、固相萃取洗脱溶剂和洗脱体积等条件。16种多环芳烃的方法检出限在0.15~0.59 ng/g,加标回收率为82%~102%,相对标准偏差(RSD,n=5)为1.1%~4.5%。19种有机氯农药的方法检出限在0.14~2.23 ng/g,加标回收率为71%~108%,相对标准偏差(RSD,n=5)为1.0%~4.5%。实际样品的测定结果表明,该方法分离效果较好,能够满足沉积物样品中多环芳烃和有机氯农药的分析要求。     

海浪预报产品数据库管理系统开发研究

本文介绍海浪预报产品数据库管理系统，包括数据库管理系统的总体设计，硬软件的配置，数据库管理系统的主要内容和解决的关键技术。该数据库管理系统的建成，提供了我国近海和西北太平洋海浪预报的系统性资料，不仅对提高海浪预报准确率提供基础资料，也给海浪中长期预测预报方法研究和区域海洋学研究带来极大帮助。     

杜氏盐藻叶绿体ATP合酶α亚单位基因启动子的克隆及初步功能分析

采用DraⅠ,EcoRⅤ,PvuⅡ,ScaⅠ,SmaⅠ和StuⅠ六种内切酶消化杜氏盐藻（Dunaliella salina）叶绿体基因组DNA,与相应DNA接头连接,构建成无载体连接的盐藻叶绿体Genome Walker DNA文库。利用长距离PCR（long distance-polymerase chain rea...     

Influence of instruments on the H/V spectral ratios of ambient vibrations

For an optimal analysis of the H/V curve, it appears necessary to check the instrument signal to noise ratio in the studied frequency band, to ensure that the signal from the ground noise is well above the internal noise. We assess the reliability and accuracy of various digitizers, sensors and/or digitizer-sensor couples. Although this study is of general interest for any kind of seismological study, we emphasize the influence of equipment on H/V analysis results. To display the impact of the instrumental part on the H/V behavior, some series of tests have been carried out following a step-by-step procedure: first, the digitizers have been tested in the lab (sensitivity, internal noise...), then the three components sensors, still in the lab, and finally the usual user digitizers-sensors couple in lab and outdoors. In general, the digitizer characteristics, verified during this test, correspond well to the manufacturer specifications, however, depending on the digitizer, the quality of the digitized waveform can be very good to very poor, with variation from a channel to another channel (gain, time difference etc.). It appears very clearly that digitizers need a warming up time before the recording to avoid problems in the low-frequency range. Regarding the sensors, we recommend strongly to avoid the use of “classical” accelerometers (i.e., usual force balance technology). The majority of tested seismometers (broadband and short period, even 4.5 Hz) can be used without problems from 0.4 to 25 Hz. In all cases, the instrumentation should be checked first to verify that it works well for the defined study aim, but also to define its limit of use (frequency, sensitivity...).     

Early Mesozoic mantle-crust transitional zone in eastern Inner Mongolia: Evidence from measurements of compressional velocities of xenoliths at high pressure and high temperature

Compression wave velocityV _p has been measured on 10 representative rock samples from the Early Mesozoic granulite and mafic-ultramafic cumulate xenoliths population from the Harqin area of the Inner Mongolia Autonomous Region (for short Inner Mongolia) as an aid to interpretingin-situ seismic velocity data and investigating velocity variation with depth in a mafic lower crust. The experiments have been carried out at constant confining pressures up to 1 000 MPa and temperatures ranging from 20 to around 1 300°C, using the ultrasonic transmission technique. After corrections for estimatedin situ crustal pressures and temperatures, elastic wave velocities range from 6.5 to 7.4 km·s^?1, indicating that they are components of the Early Mesozoic crust-mantle transitional zone. Combining with previous experimental data, we have also reestablished the Early-Mesozoic continental compression velocity profile and compared it with those of the present and of the different tectonic environments in the world. The result shows that it is similar to the velocity pattern of the extensional tectonic area, providing new clues to the Mesozoic continental structure of the North China Craton.     

Space Weather: Physics,Effects and Predictability

The time varying conditions in the near-Earth space environment that may affect space-borne or ground-based technological systems and may endanger human health or life are referred to as space weather. Space weather effects arise from the dynamic and highly variable conditions in the geospace environment starting from explosive events on the Sun (solar flares), Coronal Mass Ejections near the Sun in the interplanetary medium, and various energetic effects in the magnetosphere–ionosphere–atmosphere system. As the utilization of space has become part of our everyday lives, and as our lives have become increasingly dependent on technological systems vulnerable to the space weather influences, the understanding and prediction of hazards posed by these active solar events have grown in importance. In this paper, we review the processes of the Sun–Earth interactions, the dynamic conditions within the magnetosphere, and the predictability of space weather effects on radio waves, satellites and ground-based technological systems today.     

Deep inside a neoproterozoic intra-oceanic arc: growth,differentiation and exhumation of the Amalaoulaou complex (Gourma,Mali)

We show here that the Amalaoulaou complex, in the Pan-African belt of West Africa (Gourma, Mali), corresponds to the lower and middle sections of a Neoproterozoic intra-oceanic arc. This complex records a 90–130-Ma-long evolution of magmatic inputs and differentiation above a subducting oceanic slab. Early c. 793 Ma-old metagabbros crystallised at lower crustal or uppermost mantle depths (25–30 km) and have geochemical characteristic of high-alumina basalts extracted from a depleted mantle source slightly enriched by slab-derived sedimentary components ((La/Sm)_N < 1; ε_Nd: +5.4–6.2; ⁸⁷Sr/⁸⁶Sr: 0.7027–0.7029). In response to crustal thickening, these mafic rocks were recrystallised into garnet-granulites (850–1,000°C; 10–12 kbar) and subject to local dehydration–melting reactions, forming trondhjemititic leucosomes with garnet–clinopyroxene–rutile residues. Slightly after the granulitic event, the arc root was subject to strong HT shearing during partial exhumation (detachment faults/rifting or thrusting), coeval with the emplacement of spinel- and garnet-pyroxenite dykes crystallised from a high-Mg andesitic parental magma. Quartz and hornblende-gabbros (700–660 Ma) with composition typical of hydrous volcanic rocks from mature arcs ((La/Sm)_N: 0.9–1.8; ε_Nd: +4.6 to +5.2; ⁸⁷Sr/⁸⁶Sr: 0.7028–0.7031) were subsequently emplaced at mid-arc crust levels (~15 km). Trace element and isotopic data indicate that magmas tapped a depleted mantle source significantly more enriched in oceanic sedimentary components (0.2%). Exhumation occurred either in two stages (700–660 and 623 Ma) or in one stage (623 Ma) with a final exhumation of the arc root along cold P-T path (550°C, 6–9 kbar; epidote–amphibolite and greenschist facies conditions) during the main Pan-African collision event (620–580 Ma). The composition of magmas forming the Cryogenian Amalaoulaou arc and the processes leading to intra-arc differentiation are strikingly comparable to those observed in the deep section of exposed Mezosoic oceanic arcs, namely the Kohistan and Talkeetna complex. This evolution of the Amalaoulaou oceanic arc and its accretion towards the West African craton belong to the life and closure of the Pharusian Ocean that eventually led to the formation of the Greater Gondwana supercontinent, a similar story having occurred on the other side of the Sahara with the Mozambique Ocean.     

Hydrological cycle and water balance estimates for the megadune–lake region of the Badain Jaran Desert,China

The hydrology and water balance of megadunes and lakes have been investigated in the Badain Jaran Desert of China. Field observations and analyses of sand layer water content, field capacity, secondary salt content, and grain size reveal 3 types of important natural phenomenon: (a) vegetation bands on the leeward slope of the megadunes reflect the hydrological regime within the sandy vadose zone; (b) seepage, wet sand deposits, and secondary salt deposits indicate the pattern of water movement within the sandy vadose zone; (c) zones of groundwater seeps and descending springs around the lakes reflect the influence of the local topography on the hydrological regime of the megadunes. The seepage exposed on the sloping surface of the megadunes and gravity water contained within the sand layer confirm the occurrence of preferential flow within the vadose zone of the megadunes. Alternating layers of coarse and fine sand create the conditions for the formation of preferential flows. The preferential flows promote movement of water within the sand layer water that leads to deep penetration of water within the megadunes and ultimately to the recharging of groundwater and lake water. Our results indicate that a positive water balance promotes recharge of the megadunes, which depends on the high permeability of the megadune material, the shallow depth of the surface sand layer affected by evaporation, the occurrence of rainfall events exceeding 15 mm, and the sparse vegetation cover. Water balance estimates indicate that the annual water storage of the megadunes is about 7.5 mm, accounting for only 8% of annual precipitation; however, the shallow groundwater per unit area under the megadunes receives only 3.6% of annual precipitation, but it is still able to maintain a dynamic balance of the lake water. From a water budget perspective, the annual water storage in the megadunes is sufficient to serve as a recharge source for lake water, thereby enabling the long‐term persistence of the lakes. Overall, our findings demonstrate that precipitation is a significant component of the hydrological cycle in arid deserts.     

Variation in Coronal Activity from Solar Cycle 24 Minimum to Maximum Using Three-Dimensional Reconstructions of the Coronal Electron Density from STEREO/COR1

Three-dimensional electron density distributions in the solar corona are reconstructed for 100 Carrington rotations (CR 2054?–?2153) during 2007/03?–?2014/08 using the spherically symmetric method from polarized white-light observations with the inner coronagraph (COR1) onboard the twin Solar Terrestrial Relations Observatory (STEREO). These three-dimensional electron density distributions are validated by comparison with similar density models derived using other methods such as tomography and a magnetohydrodynamics (MHD) model as well as using data from the Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph (LASCO)-C2. Uncertainties in the estimated total mass of the global corona are analyzed based on differences between the density distributions for COR1-A and -B. Long-term variations of coronal activity in terms of the global and hemispheric average electron densities (equivalent to the total coronal mass) reveal a hemispheric asymmetry during the rising phase of Solar Cycle 24, with the northern hemisphere leading the southern hemisphere by a phase shift of 7?–?9 months. Using 14 CR (\(\approx13\)-month) running averages, the amplitudes of the variation in average electron density between Cycle 24 maximum and Cycle 23/24 minimum (called the modulation factors) are found to be in the range of 1.6?–?4.3. These modulation factors are latitudinally dependent, being largest in polar regions and smallest in the equatorial region. These modulation factors also show a hemispheric asymmetry: they are somewhat larger in the southern hemisphere. The wavelet analysis shows that the short-term quasi-periodic oscillations during the rising and maximum phases of Cycle 24 have a dominant period of 7?–?8 months. In addition, it is found that the radial distribution of the mean electron density for streamers at Cycle 24 maximum is only slightly larger (by \(\approx30\%\)) than at cycle minimum.