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1.
To further realize the action of superoxide radicals (O2− .) in photoinhibition of photosystem Ⅱ (PSⅡ), we employed 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap, associated with EPR spectroscopy, to study the effect of illumination time on O2− . formation during high light photoinhibition in PSⅡ membranes and Mn-depleted PSⅡ membranes. Results indicated that the removal of Mn cluster from PS membranes has a strong influence on the dynamics of superoxide formation. The relative mechanism was also discussed. These novel findings may further promote the studies of the structure and function of PSⅡ and the mechanism of photoinhibition. 相似文献
2.
《北京科技大学学报》2010,(1)
MgO·Al2O3 spinel type inclusions in casing steel were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).The results show that there are three forms.One is pure MgO·Al2O3 spinel,another is the composite oxide of the Mg-Al-Ca-Si-O system,and the third is the complex with oxide as a core covered by sulfide.The formation mechanisms were studied.The influences of slag basicity and vacuum degree on the magnesium content during the vacuum treatment of molten steel and furnace lining in molten steel were calculated with the coexistence theory of slag structure.The results show that the magnesium content increases with the increase in slag basicity and aluminum content in molten steel,and decreases with the increase in CO partial pressure. 相似文献
3.
In order to find the electroencephalogram (EEG) characteristic parameters typical of Alzheimer’s disease (AD) and explore an effective diagnostic method, a new mobile current multipole model was proposed to simulate the AD patient’s cortical dipole source activities. The indicators of goodness of fit (GOF) and DtononD (DD) were calculated from EEG samples to evaluate the performance of this model. Relevant results showed that this multipole model with higher GOF values and larger DD change well fitted the pathological electrical activities of cortical neurons aroused by AD’s extended sulcus and gyrus in the cerebral cortex. Meanwhile, the products of DD mean & standard variance were found in a clear linear correlation with the diagnostic data of mini-mental state examination (MMSE) used in AD clinics. Furthermore, by tracing this multipole model’s indicators in typical patients and contrasting with the functional magnetic resonance image (fMRI) as AD progressed, we suggested that the DD index may be suitable for monitoring the AD developments as a new diagnostic parameter. 相似文献
4.
In order to find the electroencephalogram (EEG) characteristic parameters typical of Alzheimer’s disease (AD) and explore an effective diagnostic method, a new mobile current multipole model was proposed to simulate the AD patient’s cortical dipole source activities. The indicators of goodness of fit (GOF) and DtononD (DD) were calculated from EEG samples to evaluate the performance of this model. Relevant results showed that this multipole model with higher GOF values and larger DD change well fitted the pathological electrical activities of cortical neurons aroused by AD’s extended sulcus and gyrus in the cerebral cortex. Meanwhile, the products of DD mean & standard variance were found in a clear linear correlation with the diagnostic data of mini-mental state examination (MMSE) used in AD clinics. Furthermore, by tracing this multipole model’s indicators in typical patients and contrasting with the functional magnetic resonance image (fMRI) as AD progressed, we suggested that the DD index may be suitable for monitoring the AD developments as a new diagnostic parameter. 相似文献
5.
The performance of axial displacement estimation in ultrasound elastography can be degraded by tissue lateral displacements,mainly because of the move-in and move-out of tissue scatterers.In our previous work,a tissue axial stretching model was proposed to separate the decorrelation effect induced by lateral displacements from other decorrelation sources.In this paper,the tissue axial stretching model is analyzed theoretically.The theoretical result in a closed form indicates that the peak value of the cross-correlation function between the pre- and post-compression echoes is determined mainly by the beam width,the beam position and the lateral strain.Computer simulations are carried out to verify the theoretical conclusion.The theoretical analysis and simulation results can help to understand more clearly the decorrelation effect of tissue lateral displacements and the 2-D spatial comprehensive cross-correlation method presented previously to reduce the decorrelation effect 相似文献
6.
The influence of embedded cell on the formation of broad acoustic band-gap in the three-component crystal slab is analyzed by calculating the acoustic transmitted energy of the epoxy resin matrix with one embedded cell, which consists of the elastically soft rubber coat and the inner core steel cylinder. It is found that the broad band-gap in the three-component crystal slab results from localization of the acoustic wave energy in the rubber coat for a broad ultrasonic frequency interval. Comparison between experiments and calculations shows good agreement. 相似文献
7.
《大庆师范学院学报》2012,32(4)
学习胡锦涛在庆祝中国共产党成立90周年大会上的讲话,借鉴延安整风的历史经验,在全党范围内,加强马克思主义理论学习和党性修养,克服"精神懈怠"的危险;大兴调查研究及理论联系实际之风,提升党的执政能力;坚持密切联系群众的作风及以人为本的执政理念,以防"脱离群众";从领导干部做起,进行批评与自我批评,敲响"消极腐败"的警钟。通过加强党的建设,保持党的先进性和纯洁性,提高党的执政能力,巩固党的执政地位。 相似文献
8.
In order to obtain more insight in the two existing mechanisms on the nucleation, i.e., sympathetic nucleation and interface instability nucleation, of α lamellae in the near β Ti alloys, the micro-texture ofα lamellae in Ti-7Mo-3Nb-3Cr-3Al has been investigated by using electron backscatter diffraction(EBSD).The results show that the α_(WGB) lamellae can not only grow up from α_(GB) grains by inheriting the orientations but also sympathetically nucleate at the α_(GB)/β interface during the slow cooling process. These observations provide the first direct experimental evidence that the formation mode of α lamellae in Ti-7333 alloy consists of sympathetic nucleation and interface instability nucleation. Based on the present results together with some previous studies on α phase transformation in Ti-based alloys the influence of β-stabilizers parameter on the change of formation mechanism of α lamellae was discussed. 相似文献
9.
An improvement of the too cold tongue in the tropical Pacific with the development of an ocean-wave-atmosphere coupled numerical model 总被引:1,自引:0,他引:1
A common problem in the application of the coupled ocean-atmosphere general circulation models (CGCMs) without flux correction is that the simulated equatorial cold tongue in general tends to be too strong, narrow, and extending too far west. The causes are not well understood yet. One possible reason may be the simulated mixed layer depth (MLD) is too shallow in the tropical Pacific due to insufficient vertical mixing in the OGCM. It is believed that the wave-induced vertical mixing can greatly improve the simulation of the MLD and thermocline structure. In this study, the coupled ocean-atmosphere general circulation model (FGCM-0) incorporated with wave-induced mixing has been employed to simulate the tropical Pacific sea surface temperature (SST). Generally, the wave-induced mixing lowers the SST in the OGCM because the strengthened vertical mixing can bring more cold water upward. However, in the coupled model, the non-uniformity of the space distribution in SST drop generates a horizontal gradient of the sea surface air pressure, and thus yields surface wind field anomaly. The wind anomaly leads to both ocean surface circulation anomaly and downwelling anomaly, which can restrain the overly-westward extension of the cold tongue in the tropical Pacific. Compared with the model results from the original model (FGCM-0), the modeled SST is higher by more than 0.8℃, with a maximum of 1.2℃ in the western Pacific (160—180°E, 0—3°N). The eastern boundary of the isotherm of 26.0℃ also moves from 165°E to 180°E. The overly westward extension of the simulated equatorial cold tongue is suppressed with the incorporation of the wave-induced mixing in the coupled model. The simulated SST shows in general improved results with a maximum improvement of more than 1.0℃. The simulated SST improvement in the north tropical Pacific is much better than that of the south tropical Pacific. 相似文献
10.
An improvement of the too cold tongue in the tropical Pacific with the development of an ocean-wave-atmosphere coupled numerical model 总被引:1,自引:0,他引:1
A common problem in the application of the coupled ocean-atmosphere general circulation models (CGCMs) without flux correction is that the simulated equatorial cold tongue in general tends to be too strong, narrow, and extending too far west. The causes are not well understood yet. One possible reason may be the simulated mixed layer depth (MLD) is too shallow in the tropical Pacific due to insufficient vertical mixing in the OGCM. It is believed that the wave-induced vertical mixing can greatly improve the simulation of the MLD and thermocline structure. In this study, the coupled ocean-atmosphere general circulation model (FGCM-0) incorporated with wave-induced mixing has been employed to simulate the tropical Pacific sea surface temperature (SST). Generally, the wave-induced mixing lowers the SST in the OGCM because the strengthened vertical mixing can bring more cold water upward. However, in the coupled model, the non-uniformity of the space distribution in SST drop generates a horizontal gradient of the sea surface air pressure, and thus yields surface wind field anomaly. The wind anomaly leads to both ocean surface circulation anomaly and downwelling anomaly, which can restrain the overly-westward extension of the cold tongue in the tropical Pacific. Compared with the model results from the original model (FGCM-0), the modeled SST is higher by more than 0.8℃, with a maximum of 1.2℃in the western Pacific (160—180°E, 0—3°N) . The eastern boundary of the isotherm of 26. 0℃also moves from 165°E to 180°E. The overly westward extension of the simulated equatorial cold tongue is suppressed with the incorporation of the wave-induced mixing in the coupled model. The simulated SST shows in general improved results with a maximum improvement of more than 1.0℃. The simulated SST improvement in the north tropical Pacific is much better than that of the south tropical Pacific. 相似文献
11.
The aggregation behavior of various acid extractants in the solvent extraction systems of metal ions is re-examined and explained according to knowledge obtained in recent work. The conclusions are as follows. (1) Complexes formed by the extractants and metal ions can form reversed micelles in organic diluents, depending on the microstructures of the complexes. The dimers of the acid extractant cannot percolate to the metal-extractant aggregates, and the acid-salt complexes are always formed in the aggregates. The reversed micelles or the W/O microemulsions formed by different species cannot be associated with each other to form a unified aggregate. (2) In solvent extraction systems, hydration of the extractants and metal ions can be considered as the driving force of forming reversed micelles. (3) Information of the first approach to the insight of the bicontinuous microemulsion of NaDEHP shows that various components in the aqueous phase behave confined and very similar to the typical AOT/n-heptane W/O microemulsions. (4) In the extraction of lanthanide ions by the W/O microemulsion of sodium naphthenate, the saponification is a process of forming reversed micelle or W/O microemulsion, while the extraction step is a process of destroying reversed micelles or W/O microemulsion droplets. 相似文献
12.
Determination of the controlled landing trajectory of Chang’E-1 satellite and the coordinate analysis of the landing point on the Moon 总被引:1,自引:0,他引:1
JinLing Li Li Guo ZhiHan Qian DongRong Jiang WeiMin Zheng XiaoYu Hong 《科学通报(英文版)》2010,55(13):1240-1245
Based on the tracking observations of radio ranges and VLBI delays of Chang’E-1 (CE-1) satellite during the controlled landing on the Moon on March 1, 2009, the landing trajectory and the coordinates of the landing point are determined by positioning analysis. It is shown that the landing epoch (the emission epoch of the last signal) of CE-1 satellite on the Moon was at UTC8h13m6.51s. The lunar longitude, latitude and surface height of the landing point in the lunar primary axes frame are respectively 52.27... 相似文献
13.
The human brain is a huge, complex system generating brain activity. The exploration of human brain function using functional magnetic resonance imaging (fMRI) is a promising method to understand brain activity. However, the complexity of the big data generated by fMRI facilitates the analysis of various levels of human brain activity, such as the distribution of neural represen- tations, the interaction between different regions, and the dynamic interaction over time. These different levels can depict distinct prospects of the human brain activity, and considerable progress has been achieved. In the future, more big data analysis methods combining advances in computer science, including larger-scale computing, machine learning, and graph theory, will promote the understanding of the human brain. 相似文献
14.
TENG Hu HUANG Xun XIU Zhilong FENG Enmin 《科学通报(英文版)》2005,50(17):1896-1903
Cell cycle is a programmed process, during which a cell proliferates to two daughter cells. The eukaryotic or-ganisms share the same characters, such as four cycle phases G1, S, G2 and M, the evolutionally conserved cell cycle proteins and its dependent kinases, and the check-points mechanism[1,2]. Due to the different functions and the complicated interactions of these proteins involved in cell cycle, it is very difficult to understand the regulatory mechanism of cell cycle in a whole sense … 相似文献
15.
Mesoscale eddy effects on the wintertime vertical mixing in the formation region of the North Pacific Subtropical Mode Water 总被引:2,自引:0,他引:2
PAN Aijun LIU Qinyu 《科学通报(英文版)》2005,50(17):1949-1956
Mesoscale eddy effects on the wintertime vertical mixing in the formation region of the North Pacific Subtropical Mode Water (NPSTMW) are studied using hydrographic data from Argo profiling floats deployed in the Kuroshio recirculation region in February and March of 2001. Anticyclonic (warm) eddy enhances the wintertime vertical mixing and results in the deep mixed layer and the deep thermocline. Consequently, a large volumetric water mass with low potential vorticity corresponding to the prototype of NPSTMW tends to be formed. By contrast, cyclonic (cold) eddy is unfavorable for the vertical mixing process and halts the deepening of the mixed layer and thus the formation of mode water. Further analysis shows that cyclonic eddies prevail in the late 1990s in the formation region of NPSTMW, which lead to significant suppression of the wintertime vertical mixing (96-98) and thus are unfavorable for the formation of NPSTMW; while the situation is completely reversed in the early 1990s (93-95). 相似文献
16.
The unsteady hydrodynamic forces and moments acting on caudal-fin models of fish with different shapes and different swing durations were experimentally measured to simulate the fish C-starts. The motion of models was characterized by rotating the model to a maximum deflection angle in an excursion time Tu and back to the initial position in a return time Td around its root-axis. Studies show that the caudal-fin plays an important role in fish C-starts and the caudal-fins with different shapes and different swing durations generate different forces and moments. In addition, the hydrodynamic forces and moments acting on the models with different shapes can be normalized by the 2nd and 3rd moments of area, respectively. The forces and moments acting on the models with different swing durations, but the same ratio of Tu to Td can also be scaled. 相似文献
17.
Quantitative assessment and analysis on the dynamic change of ecological capital in arid areas 总被引:1,自引:0,他引:1
CHEN Xi ZHANG Qing ZHOU Kefa SUN Li 《科学通报(英文版)》2006,51(A01):204-212
Ecological capital is the summation of the direct value of biological resources and the ecological service function value of ecosystems. Under the support of RS, GPS and GIS, in this paper the RS-based quantitative measurement model of assessing ecological capital is developed based on the traditional ecology theory and the research on the value of ecological capital per unit area by using the ecological parameters including Landsat TM data, CBERS satellite data, meteorological data, MODIS satellite data, land cover data and field-measured data. A case study on the spatiotemporal distribution of ecological capital in Changji Hui Autonomous Prefecture in 1990, 1995 and 2003 is carried out, and the dynamic change of ecological capital in the prefecture is measured and compared with GDP. The maps of the spatial distribution of ecological capital in the study area are charted, and the characteristics of spatial distribution of ecological capital are analyzed. The results show that the values of ecological capital in the prefecture in 1990, 1995 and 2003 were 1.47368×10^11, 1.66160×10^11 and 1.77895×10^11 yuan RMB (hereafter referred to as yuan) respectively, and that in spatial distribution, the ecological capital decreases from the alpine zones to the plains and from the oases to the deserts, which accords with the zonal distribution of vegetation in arid areas. The measured results can more objectively reflect the ecological capital and its spatial distribution in arid areas, provide an ideal foundation for further study in the future, and can also be combined with the study on service functions of ecosystems and the regiona planning as an important basis of regional planning. 相似文献
18.
Sedimentary environment of the Dajin conglomerate in Tibet, age of foraminiferan assemblages and their tectonic significance 总被引:1,自引:0,他引:1
YAN Zhen FANG Aimin PAN Yusheng LI Jiliang LIU Xiaohan YU Liangjun ZHANG Binggao 《自然科学进展(英文版)》2005,15(11):1014-1020
The Dajin conglomerate, which is one of the most important sedimentary successions of the Xigaze forearc basin in Tibet, China, consists of deep-shallow marine tuffaceous turbidites and clastic rocks bearing Nummulites, Assilina, Alveolina and Lockhartia. These fossils are very similar to the foraminiferan in the Jialazi and Maila conglomerates, and those in Gangba and Dingri areas. They developed in the Eocene. By analyzing the spatial variation of Eocene sedimentary environments of Tibet Plateau and the foraminiferan in the Dajin conglomerate, we found that Eocene sedimentation should take place on both sides of the Yarlung Tsangpo suture, and the late Eocene tectonic uplifting should make the forearc basin expose out of the sea level and begin to receive nonmarine deposits. 相似文献
19.
Zhigeng Chen 《科学通报(英文版)》2000,45(4):304-313
Based on the prerequisite that the earliest acid rock formed because of the initial global expanding tectonic processes, by
combining it with other geological limitation conditions, and starting from the lithosphere elastic mechanics, the following
is defined: the earth expansion started at about 4300 Ma ago, the average increasing rate of the earth radius is 0.40 mm/a,
the initial expanding earth radius is 4651 km, and the initial global expansion of tectonic processes happened at 4183.7 Ma
ago. From the natural and attenuation evolution condition of the earth and terrestrial planets, through the limit condition
got from the combination of the mathematics logic and the geological significance, the limited expanding earth evolution model
is established as follows:
in whichR
0= 4.651×106 m,A =1.86×106 m, β = -6.01×10−10/ a andt
s=3×108 a. From this model the maximum radiusR
maxof the limited expanding earth evolution should be 6511 km. The earth’s radius increasing rate is about 0.1 mm/a at present. 相似文献
20.
《科学通报(英文版)》2004,(23)
The volcanic rocks of the Xiong’er Group occurringwidely in the southern part of the North China Craton,overlay the Archean and Paleo-Proterozoic crystallinebasement and are overlain by middle to late Paleozoicterrigenous detrital rocks, carbonate and tillite. TheXiong’er Group crops out over an area of more than60000 km2 in a thickness ranging from 3000 to 7000 m,the largest magmatism after the formation of the crystal-line basement of the North China Craton (Fig. 1(a)). TheXiong’er … 相似文献