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PHASE DIFFERENCE BETWEEN LOW-FREQUENCY OSCILLATIONS OF CEREBRAL DEOXY-AND OXY-HEMOGLOBIN CONCENTRATIONS DURING A MENTAL TASK

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Journal of Innovative Optical Health Sciences 2011年第2期4卷 151-158页

作者： ANGELO SASSAROLI FENG ZHENG MICHELE PIERRO PETER R.BERGETHON SERGIO FANTINI Department of Biomedical Engineering Tufts University 4 Colby StreetMedfordMA 02155USA

Hemodynamic low-frequency(~0.1 Hz)spontaneous oscillations as detected in the brain by nearinfrared spectroscopy have potential applications in the study of brain activation,cerebral autoregulation,and functional connectivity.In this work,we have investigated the phase lag between oscillations of cerebral deoxy-and oxy-hemoglobin concentrations in the frequency range 0.05-0.10 Hz in a human subject during a mental workload task.We have obtained a measure of such phase lag using two different methods:(1)phase synchronization analysis as used in the theory of chaotic oscillators and(2)a novel cross-correlation phasor approach.The two methods yielded comparable initial results of a larger phase lag between low-frequency oscillations of deoxy-and oxyhemoglobin concentrations during mental workload with respect to a control,rest condition.

关键词： Phase lag oxyhemoglobin deoxyhemoglobin phase synchronization cross-correlation phasor lfo

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Main Features of Regional Circulation Variation during Onset of the South China Sea Monsoon in 1998

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Advances in Atmospheric Sciences 2000年第2期17卷 322-338页

作者：邵慧钱永甫南京大学江苏南京

In this work, the National Center for Environmental Prediction/ National Center for Atmospheic Research (NCEP/ NCAR) global daily–mean reanalysis data are used to diagnose the features of the local circulation variation during the South China Sea (SCS) monsoon in 1998. It is found that by taking the appearance of southwest wind in lower layers and east wind in upper layers as the sign of the monsoon onset, the SCS monsoon starts on May 25 in 1998, which is later than that in normal years. The formation of the SCS monsoon is not a simple propagation of southwest monsoon in the north—south direction, but a process in which the southwest wind starts first over the north of the SCS, withdraws southward, and then propagates from south to north again. During this process, both meteorological elements and circulation fields change significantly. The outbreak of the SCS monsoon is the result of the seasonal variation of the height in lower and upper layers. The air rounding the Tibetan Plateau might be one of the dynamic reasons that make the summer monsoon start over the SCS at first. At the different stages of the monsoon, the vertical circulations as well as the lower and the upper layer divergence fields undergo evident temporal and regional changes. The SCS monsoon has the 60–day, 20–30–day and 8–15–day low frequency oscillations (lfos), and dominant scale changes at the different stages of monsoon. The monsoon onset is related to the superimposition of the amplitudes of lfos with different scales. Key words SCS monsoon - Circulation variation - Regional climate - lfo Sponsored by the National Key Project of Fundamental Research SCSMEX

关键词： SCS monsoon Circulation variation Regional climate lfo

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VARIATIONS OF 30—60 DAY OSCILLATION IN ATMOSPHERE BEFORE AND DURING 1982 EL NINO

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Acta meteorologica Sinica 1991年第4期5卷 397-410页

作者：陈隆勋邵永宁 Academy of Meteorological Science State Meteorological AdministrationBeijing

By using the upper-wind data from July 1980 to June 1983,the variations of the low-frequency oscillation (lfo)in the atmosphere before and during 1982 El Nino have been investigated.Before the El Nino,the lfo propagates from west to east over the equator of the Eastern Hemisphere and from east to west over 20°N. The eastward propagating lfo over the equator consists of zonal wavenumber 1 propagating eastward and zonal wavenumber 2 with a character of stationary wave.The oscillation of zonal wavenumber 2 can modulate the oscillation strength.After the onset of the El Nino,the propagating directions of the lfo over the equator and 20°N of the Eastern Hemisphere change to be westward and eastward,respectively.The lfo over the western Pacific weakens rapidly and one coming from middle and high latitudes propagates to the equator. From the phase compositions of streamline fields for the zonal wavenumber 1 of equatorial westward propa- gatirg lfo,it is found that the atmospheric heat source in the equator of the eastern Pacific(EEP)excites a series of the equatorial cyclones and anticyclones which move northward and westward and form the westward propagating lfo over the equator.With the wavelength of 20000km,this kind of equatorial wave is similar to the mixing Rossby-gravity wave.In its westward and northward movement,the circulation in East Asia is modified.This may be the mechanism of the influence of El Nino on the climate of China.

关键词： El Nino lfo eastward propagation westward propagation

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