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991.
K Nojima K Ando H Fujiwara S Ando 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2000,25(10):2051-2056
Primary mixed cultures of astrocytes and microglia were obtained from neonatal mice, and were irradiated with high-LET carbon ions. Immunohistochemical staining showed astrocytes survived more prominently than microglia. Tagged with specific antibodies, astrocytes and microglia surviving after irradiation were counted by flow cytometry. Decreases in the number of microglia and astrocytes were detected at a dose as small as 2 Gy when Day 5 cultures were irradiated with 13 keV/micrometer carbon ions. When the cultures were irradiated on Day 10, the dose-dependent decrease of microglia was more prominent for 13 keV/micrometer carbon ions than 70 keV/micrometer carbon ions. Astrocytes showed a marginal decrease at Day 10 and Day 14. We concluded that microglia are more sensitive than astrocytes to carbon ions and X-rays, and that the radiosensitivity of microglia depends on both differentiation/proliferation status and radiation quality. 相似文献
992.
Abstract Existing methods for land surface form characterisation often focus on relatively simple landform element classifications and do not evaluate results with large scale participant experiments. This piece of research takes a semantics-grounded approach to characterising the landform valley. Based on definitions three algorithms to characterise valleys in a fuzzy way are introduced. Comparison of the results to assessments regarding the degree of being in a valley gained from over 800 participants in a questionnaire survey yields significant amounts of explained variance (R 2 = 0.35–0.37). Furthermore, accounting for very ambiguously perceived stimuli showing vast low places leads to markedly improved regressions (R 2 = 0.45–0.49), weighting of the data with a measure of uncertainty in judgment even more so (R 2 = 0.50–0.55). 相似文献
993.
Silventoinen P. Salo J. Tolsa K. Pyrhonen J. 《Aerospace and Electronic Systems Magazine, IEEE》1999,14(1):25-28
Starting and reversing times of less than 40 ms, torque ripple below ten percent and operational speeds over 5000 1/min. (rpm) can be achieved with our 6/4 prototype switched reluctance motor drive. The drive efficiency approaches 80 percent but it is currently limited by high switching frequency. Peak currents of 50 A are needed in the 4.2 kW machine. Experimental results of the prototype switched reluctance machine are shown 相似文献
994.
Time-varying autoregressive modeling of HRR radar signatures 总被引:1,自引:0,他引:1
A time-varying autoregressive (TVAR) model is used for the modeling and classification of high range resolution (HRR) radar signatures. In this approach, the TVAR coefficients are expanded by a low-order discrete Fourier transform (DFT). A least-squares (LS) estimator of the TVAR model parameters is presented, and the maximum likelihood (ML) approach for determining the model order is also presented. The validity of the TVAR modeling approach is demonstrated by comparing with other approaches in estimating time-varying spectra of synthetic signals. The estimated TVAR model parameters are also used as features in classifying HRR radar signatures with a neural network. In the experiment with two sets of noncooperating target identification (NCTI) data, about 93% of samples are correctly classified 相似文献
995.
I. V. Mingalev N. M. Astaf’eva K. G. Orlov V. M. Chechetkin V. S. Mingalev O. V. Mingalev 《Cosmic Research》2012,50(3):233-248
Mechanisms of formation of cyclonic vortices in the tropical atmosphere of the Earth are investigated in the intratropical
zone of convergence using numerical simulation made with the complete system of equations of gas dynamics taking into account
transport of infrared radiation, phase transitions of water vapor into microdrops of water and ice particles, and sedimentation
of these drops and ice particles in the field of gravity force. Observational data on the structure of dominant air streams,
which are formed in the intratropical zone of convergence over the North Atlantic in the periods of its highest thermodynamic
intensity and instability, are used in the initial and boundary conditions of the model. Formation of cyclonic vortex flows
is obtained numerically at sufficiently strong bending of the intratropical zone of convergence. The results of numerical
modeling are compared with the data of satellite microwave monitoring: global radio thermal fields of the Earth from the electronic
collection GLOBAL-Field allowing one to study the structure of atmospheric motions in a wide range of space-time scales. 相似文献
996.
Statistical studies of properties of the solar wind and interplanetary magnetic field, based on an extended database for the
period 1963–2007 including four solar cycles, show that the Gaussian approximation well suites for some parameters as the
probability distribution of their numerical values, while for others the lognormal law is preferred. This paper gives an interpretation
of these results as associated with predominance of linear or nonlinear processes in composition and interaction of various
disturbances and irregularities propagating and originating in the interior of the Sun and its atmosphere, including the solar
corona and the solar wind running away from it. Summation of independent random components of disturbances leads, according
to the central limit theorem of the probability theory, to the normal (Gaussian) distributions of quantities proper, while
their multiplication leads to the normal distributions of logarithms. Thus, one can discuss the algebra of events and associate
observed statistical distinctions with one or another process of formation of irregularities in the solar wind. Among them
there are impossible events (having null probability) and reliable events (occurring with 100% probability). For better understanding
of the relationship between algebra and statistics of events in the solar wind further investigations are necessary. 相似文献
997.
K H Hasenstein 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1999,24(6):677-685
The principle of establishing and maintaining a gravitropic set point angle depends on gravisensing and a subsequent cascade of events that result in differential elongation of the responsive structures. Since gravity acts upon masses, the gravisensing mechanisms of all biological systems must follow the same principle, namely the sensing of some force due to differential acceleration of the perceiving entity and a reference structure. This presentation will demonstrate that gravisensing can be accomplished by various means, ranging from cytoskeletal organization, mechano-elastic stress to perturbation of electric signals. However, several arguments indicate that sedimentation of either dense plastids (statoliths), the entire protoplast, or a combination of these represents the primary step in graviperception in plants. In fungi, nuclei and cytoskeletal proteins are believed to form a network capable of gravisensing but sedimenting organelles that may function as statoliths have been identified. Theoretical and practical limitations of gravisensing and detection of acceleration forces necessitate microgravity experiments to identify the primary perceptor, subsequent biochemical mechano-transduction, and biological response processes. 相似文献
998.
吴惠群 《南京航空航天大学学报(英文版)》1998,(1)
每一个机构中,员工的潜能往往被经理们所低估。如何达到公司经营的最高目标及有效地面对剧烈竞争的工商业世界,我们一定要帮助员工在机构内发挥他们最大的潜能,最后使员工及顾客均满意。怎样了解及发挥员工的内在潜能是21世纪最有效的员工管理策略,要使员工及顾客都满意,一定要知道怎样去激发员工最大潜能,并不断学习新的文化及有效地奖励员工。 相似文献
999.
1000.
The determination of the chemical composition of solid cometary dust particles was one of the prime objectives of the three
missions to Comet Halley in 1986. The dust analysis was performed by time-of-flight mass-spectrometry. Within the experimental
uncertainty the mean abundances of the rock-forming elements in cometary dust particles are comparable to their abundances
in CI-chondrites and in the solar photosphere, i.e. they are cosmic. H, C, and N, on the other hand, in cometary dust are
significantly more abundant than in CI-chondrites, approach solar abundances, are to some extent related to O, and reside
in an omnipresent refractory organic component dubbed CHON. Element variations between individual dust grains are characterized
by correlations of Mg, Si, and O, and to a lesser extent of Fe and S. From particle-to-particle variations of the rock forming
elements information on the mineralogy of cometary dust can be obtained. Cluster analysis revealed certain groups that partly
match the classifications of stratospheric interplanetary dust particles. About half of Halley's analyzed particles are characterized
by anhydrous Fe-poor Mg-silicates, Fe-sulfides, and rarely Fe metal. The Fe-poor Mg-silicates link Halley's dust to that of
Hale-Bopp as shown by recent IR observations. No significant deviation from normal of the isotopic composition of the elements is unequivocally present with the notable exception carbon: 12C-rich grains with 12C/13C-ratios up to ≈ 5,000 link cometary dust to presolar circumstellar grains identified in certain chondrites.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献