东亚赤道异常区电离层结构与扰动的CT成像

介绍东经 12 0°低纬电离层CT实验及CT重建结果 .提出一种改进的电离层CT算法 .该算法通过联合使用差分Doppler相位和差分Doppler频率数据 ,把相位积分常数估算融入重建过程之中 .CT重建结果发现 ,赤道异常峰电子密度等值线沿磁力线倾斜 ;峰位置逐日变化时 ,倾斜程度也随之改变 ,使峰电子密度等值线仍沿磁力线 ;峰朝赤道的运动通常伴随峰区展宽 .此外 ,对一次中等强度磁暴期间电离层响应的分析发现 ,在赤道异常峰区 ,磁暴急始之后 2 0min出现电子密度的深度耗空 ,这种耗空遍及从底到顶的整个F区 .结果表明 ,电离层CT技术在研究电离层赤道异常的动力过程、电离层行扰和不规则结构的时空演变以及暴时电离层响应等方面具有重要的应用价值与前景 .     

Ionospheric structure in the region of East-Asian equatorial anomaly reconstructed by tomography

A chain of low latitudinal ionospheric tomography along 120°E meridian has been operating since 1993. This chain is composed of six stations from Shanghai to Manila receiving signals from the transit NNSS satellites. In this paper several reconstruction examples are presented, which give the 2-D imaging of electron density distribution obtained from the observed TEC data by means of computerized tomography technique. In reconstruction process a multi-station method was used to determine the unknown phase offset. To overcome the limitation of incomplete projection data, a technique of backprojection in combination with a normalized ionospheric model was introduced to obtain the initial guess of electron density distribution. The results demonstrate that ionospheric tomographic technology is very useful and effective to investigate the equatorial and low-latitudinal ionospheric structures and dynamics. Supported by the National Natural Science Foundation, of China & the Science Fourdation of State Education Committee of China Xu Jisheng: born in Nov. 1946, Professor     

Rewiring cellular morphology pathways with synthetic guanine nucleotide exchange factors

Eukaryotic cells mobilize the actin cytoskeleton to generate a remarkable diversity of morphological behaviours, including motility, phagocytosis and cytokinesis. Much of this diversity is mediated by guanine nucleotide exchange factors (GEFs) that activate Rho family GTPases-the master regulators of the actin cytoskeleton. There are over 80 Rho GEFs in the human genome (compared to only 22 genes for the Rho GTPases themselves), and the evolution of new and diverse GEFs is thought to provide a mechanism for linking the core cytoskeletal machinery to a wide range of new control inputs. Here we test this hypothesis and ask if we can systematically reprogramme cellular morphology by engineering synthetic GEF proteins. We focused on Dbl family Rho GEFs, which have a highly modular structure common to many signalling proteins: they contain a catalytic Dbl homology (DH) domain linked to diverse regulatory domains, many of which autoinhibit GEF activity. Here we show that by recombining catalytic GEF domains with new regulatory modules, we can generate synthetic GEFs that are activated by non-native inputs. We have used these synthetic GEFs to reprogramme cellular behaviour in diverse ways. The GEFs can be used to link specific cytoskeletal responses to normally unrelated upstream signalling pathways. In addition, multiple synthetic GEFs can be linked as components in series to form an artificial cascade with improved signal processing behaviour. These results show the high degree of evolutionary plasticity of this important family of modular signalling proteins, and indicate that it may be possible to use synthetic biology approaches to manipulate the complex spatio-temporal control of cell morphology.     

Slip zone and energetics of a large earthquake from the Taiwan Chelungpu-fault Drilling Project

Determining the seismic fracture energy during an earthquake and understanding the associated creation and development of a fault zone requires a combination of both seismological and geological field data. The actual thickness of the zone that slips during the rupture of a large earthquake is not known and is a key seismological parameter in understanding energy dissipation, rupture processes and seismic efficiency. The 1999 magnitude-7.7 earthquake in Chi-Chi, Taiwan, produced large slip (8 to 10 metres) at or near the surface, which is accessible to borehole drilling and provides a rare opportunity to sample a fault that had large slip in a recent earthquake. Here we present the retrieved cores from the Taiwan Chelungpu-fault Drilling Project and identify the main slip zone associated with the Chi-Chi earthquake. The surface fracture energy estimated from grain sizes in the gouge zone of the fault sample was directly compared to the seismic fracture energy determined from near-field seismic data. From the comparison, the contribution of gouge surface energy to the earthquake breakdown work is quantified to be 6 per cent.     

Thyroid hormone receptor-mediated regulation of the methionine adenosyltransferase 1 gene is associated with cell invasion in hepatoma cell lines

The thyroid hormone T₃ regulates differentiation, growth, and development. We demonstrated that methionine adenosyltransferase 1A (MAT1A) was positively regulated by T₃ identified by cDNA microarray previously. The expression of the MAT1A was upregulated by T₃ in hepatoma cell lines overexpressing thyroid hormone receptors (TRs). Additionally, these findings indicate that MAT1A may be regulated by CCAAT/enhancer binding protein (C/EBP). The critical role of the C/EBP binding sites was confirmed by the reporter or chromatin immuno-precipitation (ChIP) assay. In addition, C/EBP was upregulated in hepatoma cells after T₃ treatment and ectopic expression of MAT1A inhibited cell migration and invasion in J7 hepatoma cells. Conversely, knockdown of MAT1A expression increased cell migration. Together, these findings suggest that the expression of the MAT1A gene is mediated by C/EBP and is indirectly upregulated by T₃. Finally, TR was downregulated in a small subset of hepatocellular carcinoma cells concomitantly reduced the expression of C/EBPα and MAT1A.     

ToMFIR-based fault detection approach in frequency domain

This paper is to explore further results for total measurable fault information-based residual (ToMFIR) approach to fault detection in dynamic systems. The ToMFIR contains the essential fault information and remains unaffected by control actions in a closed-loop system. It is composed of controller residual and output residual and some of further results are developed in frequency domain. Besides the ability of detecting actuator and sensor faults, it is able to detect faults/failures resulting from the computer used for control purpose that generates control signals. Currently, all of existing fault detection schemes cannot achieve the same task at all. A practical DC motor example, with a PID controller, is used to demonstrate the effectiveness of the ToMFIR-based fault detection. A comparison with the standard observer-based technique is also provided.     

The tumour suppressor Hippo acts with the NDR kinases in dendritic tiling and maintenance

Precise patterning of dendritic fields is essential for neuronal circuit formation and function, but how neurons establish and maintain their dendritic fields during development is poorly understood. In Drosophila class IV dendritic arborization neurons, dendritic tiling, which allows for the complete but non-overlapping coverage of the dendritic fields, is established through a 'like-repels-like' behaviour of dendrites mediated by Tricornered (Trc), one of two NDR (nuclear Dbf2-related) family kinases in Drosophila. Here we report that the other NDR family kinase, the tumour suppressor Warts/Lats (Wts), regulates the maintenance of dendrites; in wts mutants, dendrites initially tile the body wall normally, but progressively lose branches at later larval stages, whereas the axon shows no obvious defects. We further provide biochemical and genetic evidence for the tumour suppressor kinase Hippo (Hpo) as an upstream regulator of Wts and Trc for dendrite maintenance and tiling, respectively, thereby revealing important functions of tumour suppressor genes of the Hpo signalling pathway in dendrite morphogenesis.     

Asymmetrical response of summer rainfall in East Asia to CO2 forcing

Understanding the regional hydrological response to varying CO2 concentration is critical for cost-benefit analysis of mitigation and adaptation polices in the ...