scholarly journals Studi Hidrogeofisika Gunung Malabar Sebagai Gunung Tertinggi pada Sistem Hidrologi Cekungan Bandung

2021 ◽  
Vol 22 (4) ◽  
pp. 223
Author(s):  
Asep Harja ◽  
Farham Rezqi Ma'arif M ◽  
Maryo Dwi Nanda ◽  
Davala Attirmizzy Duvanovsky ◽  
Zhilal Ikhwana Shafa
Keyword(s):  
Catchment Area ◽  
Low Frequency ◽  
Recharge Area ◽  
Very Low Frequency

Gunung Malabar merupakan gunung tertinggi pada gugus pegunungan yang mengitari Cekungan Bandung Purba. Kawasan ini tersusun oleh berbagai pegunungan kecil, yaitu Gunung Haruman, Gunung Puntang dan dataran tinggi Pangalengan. Vegetasi di kawasan Gunung Malabar masih cukup lebat dan kawasan ini juga sering mengalami hujan dengan intensitas yang tinggi. Kondisi tersebut menjadikan Gunung Malabar sebagai recharge area dan catchment area yang ideal dengan area cukup luas. Artikel ini mengulas hasil penelitian hidrologi menggunakan metode geofisika untuk mengkaji pengaruh kawasan Gunung Malabar terhadap sistem hidrologi Cekungan Bandung Purba. Metode yang digunakan pada penelitian ini adalah Resistivitas-DC dan Very Low Frequency. Selain itu, pengukuran sifat fisik dan kimia air juga dilakukan untuk mendapatkan nilai kualitas baku mutu air permukaan berdasarkan parameter TDS, pH, dan EC. Pengukuran Resistivitas-DC dilakukan di dua wilayah yaitu di Lereng Utara Gunung Malabar, diperoleh rentang nilai resistivitas air tanah sekitar (1.4-70)Ωm, sedangkan di lereng barat Gunung Malabar, diperoleh rentang nilai resistivitas air tanah sekitar (20-150)Ωm. Kombinasi metode Resistivitas-DC dengan VLF di lereng barat Gunung Malabar menunjukkan bahwa recharge area dari sistem hidrologi di Gunung Malabar terbentuk pada zona lapisan dangkal (sekitar 15 m) dan menengah (sampai dengan 40 m). Selain itu, studi ini juga menunjukkan kualitas air tanah di kawasan Gunung Malabar. Hasil yang diperoleh dari pengukuran sifat fisik dan kimia air yaitu diperoleh rentang untuk parameter TDS dengan nilai (20-70) ppm, pH dengan rentang 6.20-8.48, dan EC dalam rentang (43-130)KataKunci : Cekungan Bandung, Gunung Malabar, Resistivitas-DC, Very Low Frequency, sifat fisik dan kimia air.

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.

scholarly journals Electromagnetic power of lightning superbolts from Earth to space

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
J.-F. Ripoll ◽  
T. Farges ◽  
D. M. Malaspina ◽  
G. S. Cunningham ◽  
E. H. Lay ◽  
...  
Keyword(s):  
Low Frequency ◽  
Optical Emission ◽  
High Energy ◽  
Very Low Frequency ◽  
Electromagnetic Power ◽  
Power Spectral ◽  
High Energy Tail ◽  
Van Allen Probes ◽  
Long Time ◽  
Low Frequency Waves

AbstractLightning superbolts are the most powerful and rare lightning events with intense optical emission, first identified from space. Superbolt events occurred in 2010-2018 could be localized by extracting the high energy tail of the lightning stroke signals measured by the very low frequency ground stations of the World-Wide Lightning Location Network. Here, we report electromagnetic observations of superbolts from space using Van Allen Probes satellite measurements, and ground measurements, and with two events measured both from ground and space. From burst-triggered measurements, we compute electric and magnetic power spectral density for very low frequency waves driven by superbolts, both on Earth and transmitted into space, demonstrating that superbolts transmit 10-1000 times more powerful very low frequency waves into space than typical strokes and revealing that their extreme nature is observed in space. We find several properties of superbolts that notably differ from most lightning flashes; a more symmetric first ground-wave peak due to a longer rise time, larger peak current, weaker decay of electromagnetic power density in space with distance, and a power mostly confined in the very low frequency range. Their signal is absent in space during day times and is received with a long-time delay on the Van Allen Probes. These results have implications for our understanding of lightning and superbolts, for ionosphere-magnetosphere wave transmission, wave propagation in space, and remote sensing of extreme events.

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