Positive interactions in communities

Current concepts of the role of interspecific interactions in communities have been shaped by a profusion of experimental studies of interspecific competition over the past few decades. Evidence for the importance of positive interactions — facilitations — in community organization and dynamics has accrued to the point where it warrants formal inclusion into community ecology theory, as it has been in evolutionary biology.

Studies on alkaloids binding to GC-rich human survivin promoter DNA using positive and negative ion electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry (ESI-MS) was used to investigate the binding of 13 alkaloids to two GC-rich DNA duplexes which are critical sequences in human survivin promoter. Negative ion ESI-MS was first applied to screen the binding of the alkaloids to the duplexes. Six alkaloids (including berberine, jatrorrhizine, palmatine, reserpine, berbamine, and tetrandrine) show complexation with the target DNA sequences. Relative binding affinities were estimated from the negative ion ESI data, and the alkaloids show a binding preference to the duplex with higher GC content. Positive ion ESI mass spectra of the complexes were also recorded and compared with those obtained in negative ion mode.

Positive- and negative-ion matrix-assisted laser desorption/ionization mass spectrometry of saccharides

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) of oligosaccharides and polysaccharides has been investigated in detail, It is demonstrated that cationized species of oligosaccharides, [M+Na](+) and [M+K](+), are dominant products under the MALDI condition, and negative ions of oligosaccharides are not formed to any significant extent in this process, The molecular masses of polysaccharides are similarly determined by positive- and negative-ion MALDI-MS with the help of column chromatography. The distinction between positive- and negative-ion MALDI mass spectra of oligo-and polysaccharides indicates that the MALDI processes for saccharides vary with molecular mass. The matrix plays a more important role in the ionization process for oligosaccharides, while in the desorption process for polysaccharides. (C) 1998 John Wiley & Sons, Ltd.

Electrochemical behaviour of spinel LiMn2O4 as positive electrode in rechargeable lithium cells

The spinel, lithium intercalation compound LiMn2O4 is prepared and studied using the techniques of a.c. impedance and cyclic voltammetry. The impedance behaviour of the LiMn2O4 electrode varies as lithium ions are intercalated or de-intercalated. The reversible behaviour of lithium ions in the LiMn2O4 electrode is confirmed by the results of cyclic voltammetry.

Evidence for positive selection in phycoerythrin genes of red algae and cyanobacteria Prochlorococcus and Synechococcus

Because of the shortage of phycoerythrin (PE) gene sequences from rhodophytes, peBA encoding beta- and alpha-subunits of PE from three species of red algae (Ceramium boydenn, Halymenia sinensis, and Plocamium telfariae) were cloned and sequenced. Different selection forces have affected the evolution of PE lineages. 8.9 % of the codons were subject to positive selection within the PE lineages (excluding high-irradiance adapted Prochlorococcus). More than 40 % of the sites may be under positive selection, and nearly 20 % sites are weakly constraint sites in high-irradiance adapted Prochlorococcus. Sites most likely undergoing positive selection were found in the chromophore binding domains, suggesting that these sites have played important roles in environmental adaptation during PE diversification. Moreover, the heterogeneous distribution of positively selected sites along the PE gene was revealed from the comparison of low-irradiance adapted Prochlorococcus and marine Synechococcus, which firmly suggests that evolutionary patterns of PEs in these two lineages are significantly different.

电离层胶片频高图数字化转换与分析研究

The ionogram acquired with the ionospheric vertical sounding method is the oldest data in the history of ionospheric research. Using of modern microelectronics and computer technology to digitalize, analyse and preserve the huge amount of historical film ionogram has become more and more important and urgent. This paper introduced the progress of the film ionogram digitalization by using digital image processing technologies to correct and repair film ionogram and convert them in an exchangeable format. An analysis and conversion software, basing on this method, has been developed for the film ionogram analysis, and then it introduces the application of this software by combining the SAO Explorer program for Wuhan film ionogram and pseudo-color ionogram in Yamagawa in Japan. It shows that our method is reliable，and the developed software is used friendly and provides a positive solution in digitalization and analysis of huge amount of historical film ionogram. Firstly, we briefly introduce the film ionogram and the process of its digitalization. By observing a amount of film ionogram, we obtain some common characteristics of the digitalized film ionogram following as: (1) the image rotation are caused by scanning; (2) the vertical axis of a large number of film ionogram exist more or less tilt and bending ; (3) coordinates of the film ionogram appear the non-uniformity phenomena result from the instability of driving motor rotation and the error of altitudinal cursor orientation. Moreover, based on the characteristics of the film ionogram and the SAO Explorer software which is widely used for the digital ionogram analysis in the world, a new method has been developed for film ionogram procession. The method contains the image geometric correction and film ionogram format conversion. The image geometric correction includes such as image rotation correction, vertical correction and coordinates scale correction. After geometric correction, the BMP file format images will be converted to the SBF file format images. Then, we also discuss the data format converting methods, which include two methods of the image data mapping basing on the normalization and logarithm, and the method of the preprocessing of the noise filtering and the threshold setting. Combining with SAO Explorer software, we successfully obtain ionospheric parameters and electron profile from the converted SBF file format digital ionograms. Based on the above method, we developed the software for the film ionogram to realize its correction analysis and conversion of the image format, and then give a introduction for its function and operation. Subsequently, the software are applied into the Wuhan film ionogram which separately observed in the high solar activity year and the low in 1980s last century. The results reveal the converted SBF digital ionogram almost preserve the all echo information of the film ionogram. Furthermore, we expressly discuss the application to the Wuhan film ionogram in 1958 in order to validate the applicability and credibility of the software. And it is showed that the important information of the film ionogram are maintained into the SBF digital ionogram. It is represented that there is credibility for conversion of the software when it applied in the older film ionogram. In sum, this software could apply to the digitalization and analysis of huge amount of historical film ionogram. Last, we extended the function of the software by bring some new conversion method and used it to apply to the pseudo-color ionogram of yamagawa in Japan. The results show that the converted ionogram information basically maintain the importantly ionogram information and the error of scaling of converted SBF file format image is almost acceptable, though there is no preprocessing for the original ionogram. Hence, we could extend the applicable range of the software and apply it to all kinds of simulative ionogram imaging by improving the method and software.

磁层－电离层电流的暴时变化以及主磁场对空间环境的影响

Two problems are studied in this thesis, the relationship of the magneto-spheric - ionospheric current systems during storms, and the effects of the main field to the space environment. The thesis includes three parts. 1. Magnetic disturbances caused by magnetospheric - ionospheric current systems Transient variations of the geomagnetic field at middle-low latitudes are mainly caused by the ionospheric dynamo current (IDC), the symmetric ring current (SRC), the partial ring current-region II field-aligned current-ionospheric current system (PRFI), and the region I field-aligned current-ionospheric current system (FACI). The storm on May 1 ～ 6, 1998 is analyzed. Firstly, the S_q-field caused by IDC current is removed by using the modified Hibberd's method in which the effect of SRC is considered. The neglect of SRC-field can give as much as 40% error in S_q-field evaluation. Secondly, the disturbance fields at the middle and low latitudes are separated according to their origins. As a result, the disturbance caused by FACI-current is an important part of the asymmetrical depression of H-component in middle and low latitudes during storms. The results show that the relative intensity of the Sq-field increases in the main phase of the storm and decreases in the recovery phase. The latitudinal gradient of the Sq-field is positive during the whole storm. The storm of May 1 ～ 6, 1998 contains two events. In the first event on May 2, the SRC-field is similar to Dst index. But in the second event on May 4 ～ 5, the SRC-field delays to Dst index, and the SRC-field depresses while the PRFI- and FACI-fields recovery. 2. Analysis of S_q~p variation in CGM coordinates In order to study the conjugation of geomagnetic variations between northern and southern hemispheres, we use the corrected geomagnetic coordinates (CGM) instead of the geomagnetic coordinates (GM) to analyze the S_q~P equivalent current system. The CGM coordinates are built up by International Geomagnetic Reference Field (IGRF) model. The S_q~p variations and equivalent current systems in the northern and southern polar regions are more symmetrical in CGM coordinates than in GM co-ordinates. This fact implies that the current distributions in polar regions are governed by the configuration of the geomagnetic field lines. As the elaborate structure of S_q~p current system in quiet time is obtained, we summarize the seasonal variation of the electrojet in quiet time. 3. The magnetospheric configuration of non-parallel-dipole model The magnetospheric configurations are calculated for two possible geomag-netic field models during the geomagnetic field reversals. These models are the dipole field with the axis to the sun and the quadrupole field model. We use the finite element method to solve the magnetic equation, and use the surface evolution method to solve the equilibrium equation. The results show that the main field greatly affects the space environment.

开发早期油藏动态地质模型与油藏工程优化研究——以埕岛油田馆上段油藏为例

In order to developing reservoir of Upper of Ng at high-speed and high-efficient in Chengdao oilfield which is located in the bally shallow sea, the paper builds up a series of theory and means predicting and descripting reservoir in earlier period of oilfield development. There are some conclusions as follows. 1. It is the first time to form a series of technique of fine geological modeling of the channel-sandy reservoir by means of mainly seismic methods. These technique include the logging restriction seismic inversion, the whole three dimension seismic interpretation, seismic properties analysis and so on which are used to the 3-dimension distributing prediction of sandy body, structure and properties of the channel reservoir by a lot of the seismic information and a small quantity of the drilling and the logging information in the earlier stage of the oil-field development. It is the first time that these methods applied to production and the high-speed development of the shallow sea oilfield. The prediction sandy body was modified by the data of new drilling, the new reservoir prediction thinking of traced inversion is built. The applied effect of the technique was very well, according to approximately 200 wells belonging to 30 well groups in Chengdao oilfield, the drilling succeeded rate of the predicting sandy body reached 100%, the error total thickness only was 8%. 2. The author advanced the thinking and methods of the forecasting residual-oil prediction at the earlier stage of production. Based on well data and seismic data, correlation of sediment units was correlated by cycle-correlation and classification control methods, and the normalization and finely interpretation of the well logging and sedimentation micro-facies were acquired. On the region of poor well, using the logging restriction inversion technique and regarding finished drilling production well as the new restriction condition, the sand body distributing and its property were predicted again and derived 3-dimension pool geologic model including structure, reservoir, fluid, reservoir engineering parameter and producing dynamic etc. According to the reservoir geologic model, the reservoir engineering design was optimized, the tracking simulation of the reservoir numerical simulation was done by means of the dynamic data (pressure, yield and water content) of development well, the production rule and oil-water distributing rule was traced, the distributing of the remaining oil was predicted and controlled. The dynamic reservoir modeling method in metaphase of development was taken out. Based on the new drilling data, the static reservoir geologic model was momentarily modified, the research of the flow units was brought up including identifying flow units, evaluating flow units capability and establishing the fine flow units model; according to the dynamic data of production and well testing data, the dynamic tracing reservoir description was realized through the constant modification of the reservoir geologic model restricted these dynamic data by the theory of well testing and the reservoir numerical simulation. It was built the dynamic tracing reservoir model, which was used to track survey of the remaining oil on earlier period. The reservoir engineering tracking analysis technique on shallow sea oilfield was founded. After renewing the structure history since tertiary in Chengdao area by the balance section technique and estimating the activity character of the Chengbei fault by the sealing fault analysis technique, the meandering stream sediment pattern of the Upper of Ng was founded in which the meandering border was the uppermost reservoir unit. Based on the specialty of the lower rock component maturity and the structure maturity, the author founded 3 kinds of pore structure pattern in the Guanshang member of Chengdao oil-field in which the storing space mainly was primary (genetic) inter-granular pore, little was secondary solution pore and the inter-crystal pore tiny pore, and the type of throat mainly distributed as the slice shape and the contract neck shape. The positive rhythmic was briefly type included the simple positive rhythm, the complex positive rhythm and the compound rhythm. Interbed mainly is mudstone widely, the physical properties and the calcite interbed distribute localized. 5. The author synthetically analyzed the influence action of the micro-heterogeneity, the macro-heterogeneity and the structure heterogeneity to the oilfield water flood development. The efficiency of water flood is well in tiny structure of convex type or even type at top and bottom in which the water breakthrough of oil well is soon at the high part of structure when inject at the low part of structure, and the efficiency of water flood is poor in tiny structure of concave type at top and bottom. The remaining oil was controlled by sedimentary facies; the water flooding efficiency is well in the border or channel bar and is bad in the floodplain or the levee. The separation and inter layer have a little influence to the non-obvious positive rhythm reservoir, in which the remaining oil commonly locate within the 1-3 meter of the lower part of the separation and inter layer with lower water flooding efficiency.

Toeplitz矩阵的循环延拓及其分析与应用

In this paper, we have presented the combined preconditioner which is derived from k =±-1~(1/2) circulant extensions of the real symmetric positive-definite Toeplitz matrices, proved it with great efficiency and stability and shown that it is easy to make error analysis and to remove the boundary effect with the combined preconditioner. This paper has also presented the methods for the direct and inverse computation of the real Toeplitz sets of equations and discussed many problems correspondingly, especially replaced the Toeplitz matrices with the combined preconditoners for analysis. The paper has also discussed the spectral analysis and boundary effect. Finally, as an application in geophysics, the paper makes some discussion about the squared root of a real matrix which comes from the Laplace algorithm.