Weighing the cusp at the Galactic Centre

As stars close to the galactic centre have short orbital periods it has been possible to trace large fractions of their orbits in the recent years. Previously the data of the orbit of the star S2 have been fitted with Keplerian orbits corresponding to a massive black hole (MBH) with a mass of M_BH = 3–4 × 10⁶M_⊙ implying an insignificant cusp mass. However, it has also been shown that the central black hole resides in a ∼1″ diameter stellar cluster of a priori unknown mass. In a spherical potential which is neither Keplerian nor harmonic, orbits will precess resulting in inclined rosetta shaped trajectories on the sky. In this case, the assumption of non‐Keplerian orbits is a more physical approach. It is also the only approach through which cusp mass information can be obtained via stellar dynamics of the cusp members. This paper presents the first exemplary modelling efforts in this direction. Using positional and radial data of star S2, we find that there could exist an unobserved extended mass component of several 10⁵M_⊙ forming a so‐called ‘cusp’ centered on the black hole position. Considering only the fraction of the cusp mass Mequation/tex2gif-inf-4.gif within the apo‐center of the S2 orbit we find as an upper limit that Mequation/tex2gif-inf-6.gif/(M_BH + Mequation/tex2gif-inf-9.gif) ≤ 0.05. A large extended cusp mass, if present, is unlikely to be composed of sub‐solar mass constituents, but could be explained rather well by a cluster of high M/L stellar remnants, which we find to form a stable configuration. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The impact of the South–North Water Transfer Project (CTP)'s central route on groundwater table in the Hai River basin,North China

The central route of the South–North Water Transfer Project (CTP) is designed to divert approximately 9.5 billion m³ of water per year from the Han River, a major tributary of the Yangtze River, to the Hai River basin in the north China. The main purpose of this study is to assess the impact of CTP on groundwater table in the Hai River basin. Our study features a large‐scale distributed hydrological model that couples a physically based groundwater module, which is sub‐basin‐based, with a conceptual surface water module, which is grid‐based. There are several grids in each sub‐basin and water exchange among grid that are considered. Our model couples surface water module and groundwater module and calculates human water use at the same time. The simulation results indicate that even with the water supply by CTP, the groundwater table will continue to decline in the Hai River basin. However, the CTP water can evidently reduce the decline rate, helping alleviate groundwater overexploitation in Hai River region. Copyright © 2013 John Wiley & Sons, Ltd.     

Petrological constraints on the tectonic setting of the Kathmandu Nappe in the Langtang–Gosainkund–Helambu regions,Central Nepal Himalaya

The Gosainkund–Helambu region in central Nepal occupies a key area for the development of Himalayan kinematic models, connecting the well‐investigated Langtang area to the north with the Kathmandu Nappe (KN), whose interpretation is still debated, to the south. In order to understand the structural and metamorphic architecture of the Greater Himalayan Sequence (GHS) in this region, a detailed petrological study was performed, focusing on selected metapelite samples from both the Gosainkund–Helambu and Langtang transects. The structurally lowest sample investigated belongs to the Lesser Himalayan Sequence; its metamorphic evolution is characterized by a narrow hairpin P–T path with peak P–T conditions of 595 ± 25 °C, 7.5 ± 1 kbar. All of the other samples here investigated belong to the GHS. Along the Langtang section, two tectono‐metamorphic units have been distinguished within the GHS: the Lower Greater Himalayan Sequence (L‐GHS), characterized by peak P–T conditions at 728 ± 11 °C, 10 ± 0.5 kbar (corresponding to a T/depth ratio of 22 ± 1 °C km^?1), and the structurally higher Upper Greater Himalayan Sequence, with peak metamorphic conditions at 780 ± 20 °C, 7.8 ± 0.8 kbar (corresponding to a T/depth ratio of 31 ± 4 °C km^?1). This confirms the existence of a main tectono‐metamorphic discontinuity within the GHS, as previously suggested by other authors. The results of petrological modelling of the metapelites from the Gosainkund–Helambu section show that this region is entirely comprised within a sub‐horizontal and thin L‐GHS unit: the estimated peak metamorphic conditions of 734 ± 19 °C, 10 ± 0.8 kbar correspond to a uniform T/depth ratio of 23 ± 3 °C km^?1. The metamorphic discontinuity identified along the Langtang transect and dividing the GHS in two tectono‐metamorphic units is located at a structural level too high to be intersected along the Gosainkund–Helambu section. Our results have significant implications for the interpretation of the KN and provide a contribution to the more general discussion of the Himalayan kinematic models. We demonstrate that the structurally lower unit of the KN (known as Sheopuri Gneiss) can be correlated with the L‐GHS unit; this result strongly supports those models that correlate the KN to the Tethyan Sedimentary Sequence and that suggest the merging of the South Tibetan Detachment System and the Main Central Thrust on the northern side of the KN. Moreover we speculate that, in this sector of the Himalayan chain, the most appropriate kinematic model able to explain the observed tectono‐metamorphic architecture of the GHS is the duplexing model, or hybrid models which combine the duplexing model with another end‐member model.     

赣中抚州—永丰断裂新构造活动踪迹及其找矿意义

抚州—永丰断裂作为江西省德兴—遂川断裂带的组成部分,通常认为是一条长期活动的控岩控盆控矿断裂。研究发现,该断裂在挽近时期具有明显新构造活动的踪迹,如清晰的线性影像、构造地貌单元分界线与断裂走向一致、具有地震活动纪录、温泉沿断裂分布等,表明该断裂是新构造。断层角砾岩特征及地层错移关系显示为右行正断层,南东盘向南东方向下滑,致使断裂两侧侵蚀深度或保矿条件明显不同:北西侧处上升盘,侵蚀深度较大,玉华山盆地体找铀潜力受限;南东侧处下降盘,侵蚀深度较小,上白垩统红层较厚,保矿条件良好,相山矿田北西部及红层深部具有较大的找铀远景。     

旅游中心城市相关概念辨析

旅游中心城市概念源于旅游中心地,旅游中心地则是中心地理论在旅游业中的应用。通过对旅游中心地、旅游中心城市、旅游集散地、旅游目的地等概念的系统梳理与逻辑思辨,归纳出如下观点:旅游中心城市属于旅游中心地的一个种类,它以供给旅游服务为核心职能,旅游服务功能的中心性大小决定了其在区域旅游中的地位。在严格意义上,它不等同于中心城市,常表现为旅游集散地和旅游服务中心,但未必是游客的终极旅游目的地。旅游中心城市常将集旅游吸引中心和旅游服务中心两大功能于一体作为其理想发展目标。     

Mean Flow–Storm Track Relationship and Rossby Wave Breaking in Two Types of El-Nino简

The features of large-scale circulation, storm tracks and the dynamical relationship between them were examined by investigating Rossby wave breaking （RWB） processes associated with Eastern Pacific （EP） and Central Pacific （CP） E1-Nifio. During EP E1-Nino, the geopotential height anomaly at 500 hPa （Z500） exhibits a Pacific-North America （PNA） pattern. During CP EI-Nifio, the Z500 anomaly shows a north positive-south negative pattern over the North Pacific. The anomalous distributions of baroclinicity and storm track are consistent with those of upper-level zonal wind for both EP and CP EI-Nino, suggesting impacts of mean flow on storm track variability. Anticyclonic wave breaking （AWB） oczurs less frequently in EP EI-Nino years, while cyclonic wave breaking （CWB） occurs more frequently in CP EI-Nino years over the North Pacific sector. Outside the North Pacific, more CWB events occur over North America during EP Ei-NiNo. When AWB events occur less frequently over the North Pacific during EP EI-Nino, Z500 decreases locally and the zonal wind is strengthened （weakened） to the south （north）. This is because AWB events reflect a monopoie high anomaly at the centroid of breaking events. When CWB events occur more frequently over the North Pacific under CP EI-Nino conditions, and over North America under EP EI-Nino condition, Z500 increases （decreases） to the northeast （southwest）, since CWB events are related to a northeast-southwest dipole Z500 anomaly. The anomalous RWB events act to invigorate and reinforce the circulation anomalies over the North Pacific-North America region linked with the two types of EI-Nino.     

Statistical Characteristics of ENSO Events in CMIP5 Models

By applying the historical-run outputs from 24 Coupled Model Intercomparison Project Phase 5（CMIP5） models and the NOAA Extended Reconstructed SST V3 b dataset（ERSST）, the characteristics of different types of ENSO in the selected CMIP5 models, including cold-season-matured Eastern Pacific（C-EP） ENSO, warmseason-matured EP（W-EP） ENSO, cold-season-matured Central Pacific（C-CP） ENSO, and warm-season-matured CP（W-CP） ENSO, were examined in comparison with those in the ERSST dataset. The results showed that, in general, consistent with observations, EP ENSO events in most of the model runs were relatively much stronger than CP ENSO events, and cold-season-matured ENSO events were relatively much more frequent than warm-season-matured ENSO events for both EP and CP ENSO events. The composite amplitudes of ENSO events in most of the models were generally weaker than in observations, particularly for EP El Ni？o and CP La Ni？a. Moreover, most of the models successfully reproduced the amplitude asymmetries between El Ni？o and La Ni？a for cold-season-matured EP and CP ENSO events, exhibiting an average stronger/weaker EP El Ni？o/La Ni？a regime and a weaker/stronger CP El Ni？o/La Ni？a regime. Most of the models, however, failed to reproduce the observed regimes of stronger/weaker W-EP El Ni？o/ La Ni？a and weaker/stronger W-CP El Ni？o/La Ni？a.     

Effects of topography and land use on woody plant species composition and beta diversity in an arid Trans-Himalayan landscape,Nepal

Distribution patterns of plant species are believed to be impacted by small-scale habitat heterogeneity. However, there have been few comparative studies examining how woody vegetation composition and diversity varies with aspects of different orientations in the Trans-Himalayan region at a local scale. Here, we examined the effects of incoming solar radiation on variation in woody species composition and compared the diversity between the northeast- and southwest-facing slopes in a Trans-Himalayan valley of Nepal. We also examined the implicit interactions between slope orientation and land use in determining the compositional variations between the slopes. We selected two pairs of northeast- and southwest-facing slopes where the first pair has a similar land use and differs in exposure only（Pisang site） while the other pair has clear differences in land use in addition to slope exposure（Braka site）. In each site, we sampled 72 plots（36 on each slope） in which the presence and absence of woody species, environmental variables, and disturbance were recorded. Correspondence Analysis（CA） results suggested that the woody species composition significantly varied between northeast- and southwest-facing slopes at both sites, and was significantly correlated with measured environmental variables such as radiation index, altitude, and canopy openness. In the Braka site,mean alpha diversity was significantly higher on southwest-facing slopes. In contrast, beta diversity and gamma diversity were greater on northeast-facing slopes at both sites. Our results suggest that topographic variables（e.g., radiation index） affect species composition between the slopes, likely due to their influence on small scale abiotic environmental variables. However, the effects of land use, such as livestock browsing/grazing may interact with the effects of slope exposure, effectively reducing differences in species composition within slopes but enhancing the differences in beta diversity between contrasting slopes in the Br     

内蒙古中部地区中-新元古代黑色岩系中的金矿床及找矿远景

内蒙古中部地区中—新元古代黑色岩系发育,形成于渣尔泰-白云鄂博裂陷槽内,命名为渣尔泰群和白云鄂博群。目前,仅在白云鄂博群的黑色岩系中发现并勘查了一批原生金矿。矿石主要类型为细脉型和蚀变变质岩型。金矿受层位和构造破碎带控制,金平均品位低,可形成大型或超大型矿床。因此,内蒙古中部中—新元古代黑色岩系中金矿资源潜力大,找矿远景好。     

基于流强度的中国城市对外服务能力时空演变特征

综合运用城市流强度模型、改良Theil系数和K-means时空聚类法对2004~2010年中国地级以上286个城市对外服务能力的时空演变特征进行探讨,得到以下结论:1城市流强度值的绝对量均有明显上升,但存在显著的区域非均衡现象,并与城市经济实力有较高的相关性。2省内差异对城市对外服务能力的差异贡献率在58%~72%,是其空间尺度差异的主要来源。3时空演变表现出明显的阶段性和等级性规律,且空间等级性特征随阶段演进更趋明显。4对外服务能力的强弱和集聚强化趋势与城市流强度基数值大小和增速快慢有着紧密关系,一定程度上体现了基础乘数效应和循环累积效应配置下的非均衡特征。