نتایج جستجو برای: signal fluctuations
تعداد نتایج: 486265 فیلتر نتایج به سال:
The traditional magnetic storage mechanisms ~both analog and digital! apply an external field signal H(t) to a hysteretic magnetic material, and read the remanent magnetization M (t), which is ~roughly! proportional to H(t). We propose a new analog method of recovering the signal from the magnetic material, making use of the shape of the hysteresis loop M (H). The field H , ‘‘stored’’ in a regi...
Functional magnetic resonance imaging (fMRI) studies of the human brain have suggested that low-frequency fluctuations in resting fMRI data collected using blood oxygen level dependent (BOLD) contrast correspond to functionally relevant resting state networks (RSNs). Whether the fluctuations of resting fMRI signal in RSNs are a direct consequence of neocortical neuronal activity or are low-freq...
We report the first detection of the gravitational lensing of the cosmic microwave background through a measurement of the four-point correlation function in the temperature maps made by the Atacama Cosmology Telescope. We verify our detection by calculating the levels of potential contaminants and performing a number of null tests. The resulting convergence power spectrum at 2° angular scales ...
Functional MRI resting state and connectivity studies of brain focus on neural fluctuations at low frequencies which share power with physiological fluctuations originating from lung and heart. Due to the lack of automated software to process physiological signals collected at high magnetic fields, a gap exists in the processing pathway between the acquisition of physiological data and its use ...
Resting state low frequency (<0.08 Hz) fluctuations in MR timecourses that are temporally correlated between functionally related areas have been observed in recent studies. These fluctuations have been assumed to arise from spontaneous blood oxygenation level-dependent (BOLD) oscillations. This work examines the T*2 characteristics of the low frequency fluctuations (functional connectivity) an...
A fundamental requirement in the new generation of high resolution Cosmic Microwave Background imaging experiments is a strict control of systematic errors that must be kept at μK level in the final maps. Some of these errors are of celestial origin, while others will be generated by periodic fluctuations of the satellite environment. These environment instabilities will cause fluctuations in t...
We present a vector theory of Raman amplification and use it to discuss the effect of polarization-mode dispersion (PMD) on the Raman gain process inside the optical fiber used for stimulated Raman scattering. We show that the PMD induces large fluctuations in the amplified signal and reduces the average value of the amplifier gain. In the case of forward pumping, fluctuations are expected to b...
Isogenic cells sensing identical external signals can take markedly different decisions. Such decisions often correlate with pre-existing cell-to-cell differences in protein levels. When not neglected in signal transduction models, these differences are accounted for in a static manner, by assuming randomly distributed initial protein levels. However, this approach ignores the a priori non-triv...
The presence of spontaneous BOLD fMRI signal fluctuations in human grey matter compromises the detection and interpretation of evoked responses and limits the sensitivity gains that are potentially available through coil arrays and high field systems. In order to overcome these limitations, we adapted and improved a recently described correlated noise suppression method (de Zwart et al., 2008),...
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