A 5,600-year-old wooden well in Zhejiang Province,China

In 1973, traces of China’s early Neolithic Hemudu culture (7,000–5,000 BP) were discovered in the village of Hemudu in Yuyao County, Zhejiang Province, in the lower Yangtze River coastal plain. The site has yielded animal and plant remains in large quantities and large numbers of logs secured with tenon and mortise joints, commonly used in wooden buildings and other wooden structures. For hydrogeologists, the most interesting structure is an ancient wooden well. The well is believed to be about 5,600 years old, which makes it the oldest wooden well yet found in China. The well site contains over 200 wooden components and can be divided into inner and outer parts. The outer part consists of 28 piles around a pond. The inner part, the wooden well itself, lies in the middle of the pond. The walls of the well were lined with close-set timber piles reinforced by a square wooden frame. The 28 piles in the outer part of the site may have been part of a shelter for the well, suggesting that the people of the Hemudu culture were already concerned with water hygiene and protection of their water source.     

The effectiveness of the Kozai mechanism in the Galactic Centre

I examine the effectiveness of Kozai oscillations in the centres of galaxies and in particular the Galactic Centre (GC) using standard techniques from celestial mechanics. In particular, I study the effects of a stellar bulge potential and general relativity on Kozai oscillations, which are induced by stellar discs. Löckmann et al. recently suggested that Kozai oscillations induced by the two young massive stellar discs in the GC drive the orbits of the young stars to large eccentricity  ( e ≈ 1)  . If some of these young eccentric stars are in binaries, they would be disrupted near pericentre, leaving one star in a tight orbit around the central supermassive black hole and producing the S-star population. I find that the spherical stellar bulge suppresses Kozai oscillations, when its enclosed mass inside a test body is of the order of the mass in the stellar disc(s). Since the stellar bulge in the GC is much larger than the stellar discs, Kozai oscillations due to the stellar discs are likely suppressed. Whether Kozai oscillations are induced from other non-spherical components to the potential (e.g. a flattened stellar bulge) is yet to be determined.     

GMRT observations of four suspected supernova remnants near the Galactic Centre

We have observed two fields – Field I     ,     and Field II     ,     – with the Giant Metrewave Radio Telescope (GMRT) at 330 MHz. In the first field, we have studied the candidate supernova remnant (SNR) G3.1−0.6 and, based on its observed morphology, spectral index and polarization, confirmed it to be an SNR. We find this supernova to have a double ring appearance with a strip of emission on its western side passing through its centre.
We have discovered two extended curved objects in the second field, which appears to be part of a large shell-like structure. It is possibly the remains of an old supernova in the region. Three suspected SNRs, G356.3−0.3, G356.6+0.1 and G357.1−0.2, detected in the MOST 843-MHz survey of the GC region appear to be located on this shell-like structure. While both G356.3−0.3 and G356.6+0.1 seem to be parts of this shell, G357.1−0.2, which has a steeper spectrum above 1 GHz, could be a background SNR seen through the region. Our H  i absorption observation towards the candidate SNR G357.1−0.2 indicates that it is at a distance of more than 6 kpc from us.     

Structure of the Malpelo Ridge (Colombia) from seismic and gravity modelling

Wide-angle and multichannel seismic data collected on the Malpelo Ridge provide an image of the deep structure of the ridge and new insights on its emplacement and tectonic history. The crustal structure of the Malpelo Ridge shows a 14 km thick asymmetric crustal root with a smooth transition to the oceanic basin southeastward, whereas the transition is abrupt beneath its northwestern flank. Crustal thickening is mainly related to the thickening of the lower crust, which exhibits velocities from 6.5 to 7.4 km/s. The deep structure is consistent with emplacement at an active spreading axis under a hotspot like the present-day Galapagos Hotspot on the Cocos-Nazca Spreading Centre. Our results favour the hypothesis that the Malpelo Ridge was formerly a continuation of the Cocos Ridge, emplaced simultaneously with the Carnegie Ridge at the Cocos-Nazca Spreading Centre, from which it was separated and subsequently drifted southward relative to the Cocos Ridge due to differential motion along the dextral strike-slip Panama Fracture Zone. The steep faulted northern flank of the Malpelo Ridge and the counterpart steep and faulted southern flank of Regina Ridge are possibly related to a rifting phase that resulted in the Coiba Microplate’s separation from the Nazca Plate along the Sandra Rift.     

Optical Gravitational Lensing Experiment OGLE-1999-BUL-32: the longest ever microlensing event – evidence for a stellar mass black hole?

We describe the discovery of the longest microlensing event ever observed, OGLE-1999-BUL-32, also independently identified by the MACHO collaboration as MACHO-99-BLG-22. This unique event has an Einstein radius crossing time of 640 d. The high-quality data obtained with difference image analysis shows a small but significant parallax signature. This parallax effect allows one to determine the Einstein radius projected on to the observer plane as     . The transverse velocity projected on to the observer plane is about 79 km s⁻¹. We argue that the lens is likely to have a mass of at least a few solar masses, i.e. it could be a stellar black hole. The black hole hypothesis can be tested using the astrometric microlensing signature with the soon-to-be installed Advanced Camera for Surveys on board the Hubble Space Telescope . Deep X-ray and radio images may also be useful for revealing the nature of the object.     

泉州中心城区地质环境与城市发展浅论

在分析泉州中心城区地质环境特征的基础上,将中心城区地质环境分为３个区,最后从城市发展角度对各区主要地质环境问题提出对策和建议。     

区域地震信息网络系统的分步实现

文中对区域地震信息网络系统的“九五”目标和现实之间的矛盾进行了分析。为了有效地利用资金,结合地震系统现状及发展趋势,提出了从易到难的分步实现方案,并介绍了辽宁省地震局的初步实验结果。