scholarly journals Spatial distribution of very low‐frequency wind‐generated noise in the ocean

1980 ◽  
Vol 67 (S1) ◽  
pp. S96-S96
Author(s):  
F. Ingenito ◽  
W. A. Kuperman
Keyword(s):  
Spatial Distribution ◽  
Low Frequency ◽  
Very Low Frequency

Modeling and inversion of magnetic and VLF-EM data with an application to basement fractures: A case study from Raigarh, India

Geophysics ◽  
2007 ◽  
Vol 72 (5) ◽  
pp. B133-B140 ◽  
Author(s):  
V. Ramesh Babu ◽  
Subhash Ram ◽  
N. Sundararajan
Keyword(s):  
Spatial Distribution ◽  
Low Frequency ◽  
Analytical Signal ◽  
Magnetic Data ◽  
Fracture Zones ◽  
Very Low Frequency ◽  
Subsurface Resistivity ◽  
Spatial Locations ◽  
And Inversion

We present modeling of magnetic and very low frequency electromagnetic (VLF-EM) data to map the spatial distribution of basement fractures where uranium is reported in Sambalpur granitoids in the Raigarh district, Chhattisgarh, India. Radioactivity in the basement fractures is attributed to brannerite, [Formula: see text] complex, and uranium adsorbed on ferruginous matter. The amplitude of the 3D analytical signal of the observed magnetic data indicates the trend of fracture zones. Further, the application of Euler 3D deconvolution to magnetic data provides the spatial locations and depth of the source. Fraser-filtered VLF-EM data and current density pseudosections indicate the presence of shallow and deep conductive zones along the fractures. Modeling of VLF-EM data yields the subsurface resistivity distribution of the order of less than 100 ohm-m of the fractures. The interpreted results of both magnetic and VLF-EM data agree well with the geologic section obtained from drilling.

The Attenuation of Very Low Frequency Brain Oscillations in Transitions from a Rest State to Active Attention

2009 ◽  
Vol 23 (4) ◽  
pp. 191-198 ◽  
Author(s):  
Suzannah K. Helps ◽  
Samantha J. Broyd ◽  
Christopher J. James ◽  
Anke Karl ◽  
Edmund J. S. Sonuga-Barke
Keyword(s):  
Brain Activity ◽  
Sampling Rate ◽  
Low Frequency ◽  
Future Research ◽  
Adhd Symptoms ◽  
Default Mode ◽  
Very Low Frequency ◽  
Wide Range ◽  
Interference Hypothesis ◽  
Mode Interference

Background: The default mode interference hypothesis ( Sonuga-Barke & Castellanos, 2007 ) predicts (1) the attenuation of very low frequency oscillations (VLFO; e.g., .05 Hz) in brain activity within the default mode network during the transition from rest to task, and (2) that failures to attenuate in this way will lead to an increased likelihood of periodic attention lapses that are synchronized to the VLFO pattern. Here, we tested these predictions using DC-EEG recordings within and outside of a previously identified network of electrode locations hypothesized to reflect DMN activity (i.e., S3 network; Helps et al., 2008 ). Method: 24 young adults (mean age 22.3 years; 8 male), sampled to include a wide range of ADHD symptoms, took part in a study of rest to task transitions. Two conditions were compared: 5 min of rest (eyes open) and a 10-min simple 2-choice RT task with a relatively high sampling rate (ISI 1 s). DC-EEG was recorded during both conditions, and the low-frequency spectrum was decomposed and measures of the power within specific bands extracted. Results: Shift from rest to task led to an attenuation of VLFO activity within the S3 network which was inversely associated with ADHD symptoms. RT during task also showed a VLFO signature. During task there was a small but significant degree of synchronization between EEG and RT in the VLFO band. Attenuators showed a lower degree of synchrony than nonattenuators. Discussion: The results provide some initial EEG-based support for the default mode interference hypothesis and suggest that failure to attenuate VLFO in the S3 network is associated with higher synchrony between low-frequency brain activity and RT fluctuations during a simple RT task. Although significant, the effects were small and future research should employ tasks with a higher sampling rate to increase the possibility of extracting robust and stable signals.

VLF/LF (Very Low Frequency/Low Frequency) Reflection Properties of the Low Latitude Ionosphere

1988 ◽  
Author(s):  
Wayne I. Klemetti ◽  
Paul A. Kossey ◽  
John E. Rasmussen ◽  
Maria Sueli Da Silveira Macedo Moura
Keyword(s):  
Low Frequency ◽  
Low Latitude ◽  
Very Low Frequency ◽  
Low Latitude Ionosphere

scholarly journals Chromosome breakage undetectable in active Mu lines of maize.

Genetics ◽  
1989 ◽  
Vol 122 (1) ◽  
pp. 205-209
Author(s):  
L J Rowland ◽  
D S Robertson ◽  
J Strommer
Keyword(s):  
Transposable Elements ◽  
Low Frequency ◽  
Chromosome Breakage ◽  
Very Low Frequency ◽  
Induced Mutants ◽  
Simultaneous Loss

Abstract We have used a set of Mutator-induced mutants of Bz1 to test whether members of the Mutator (Mu) family of maize transposable elements produce broken chromosomes. From our inability to demonstrate the simultaneous loss of two dominant endosperm markers distal to Mu insertions at Bz1 we conclude that either Mu, unlike many elements of the Ds family, does not induce such breaks, or it does so at a very low frequency.

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