نتایج جستجو برای: روش vlf
تعداد نتایج: 370741 فیلتر نتایج به سال:
پدیدههای الکترومغناطیسی ازجمله اختلال در سیگنالهای رادیویی (VLF, Very Low Frequency) برای پیشبینی کوتاهمدت زمینلرزه از چند سال پیش در دنیا مورداستفاده قرارگرفتهاند. سیگنالهای VLF از مرز پایینی یونوسفر بازتاب مییابند بنابراین هر تغییری در منطقه D یونوسفر شرایط بازتاب امواج VLF را تغییر میدهد. احتمالاً یکی از عواملی که پارامترهای مختلف یونوسفر را تحتتأثیر قرار میدهد، فرآیندهای اطراف کان...
We compared the contribution of metabotropic glutamate receptors (mGluRs) to the generation and modulation of synaptic responses elicited in intracellularly recorded L5 motoneurons from neonatal rats by segmental and descending fibers. Dorsal root (DR) stimulation at high intensity (C-fiber strength) evoked long latency (2-5-s) depolarization in addition to early monosynaptic and polysynaptic r...
In patients with migraine with or without aura the prophylactic effect of amitriptyline (AMT) and venlafaxine (VLF) was compared in a randomized double-blind crossover study. Intolerable side effects resulted in drop out of five patients on AMT (due to hypersomnia, difficulty in concentration and orthostatic hypotension) and one patient on VLF (because of nausea and vomiting). Following the run...
It is recently recognized that the ionosphere is very sensitive to seismic effects, and the detection of ionospheric perturbations associated with earthquakes, seems to be very promising for short-term earthquake prediction. We have proposed a possible use of VLF/LF (very low frequency (3-30 kHz) /low frequency (30-300 kHz)) radio sounding of the seismo-ionospheric perturbations. A brief histor...
Results of a cross-sectional study of ventilatory lung function (VLF) in a group of 307 working men showed that the leukocyte count in peripheral blood is more closely associated with the relative position (percentile) of a person in the frequency distribution of VLF than is smoking intensity. Leukocyte count is significantly (and inversely) correlated with VLF in nonsmokers as well as in smoke...
[1] ELF/VLF radio waves (300 Hz–30 kHz) are difficult to generate with practical antennae, because of their extraordinarily long (10–1000 km) wavelengths, and the lossy nature of the Earth’s surface at these frequencies. ELF/VLF waves have been successfully generated via amplitude modulated (AM) HF (2–10 MHz) heating of the lower ionosphere. Through the temperature-dependent conductivity of the...
The attenuation of VLF signals from lightning and ground-based VLF transmitters during transionospheric propagation has been the subject of recent interest, as discrepancies have been found between satellite data and model calculations. Previous modeling efforts, however, have not considered the self-absorption effect due to nonlinear heating and ionization in the lower ionosphere. A self-consi...
[1] Observations show that intense +CG lightning discharges which trigger both an elve and a sprite are associated with long-lasting conductivity modifications in the upper D-region ionosphere. They are observed as strong perturbations in VLF signals propagating through the disturbed region, manifested as LOng Recovery Early VLF events (LORE), which can last up to 30 minutes. These same ionosph...
[1] Modulated high frequency (HF) heating of the lower ionosphere in the presence of auroral electrojet currents has become an important method for generating electromagnetic waves in the extremely‐low frequency (ELF) and very‐low frequency (VLF) bands. Recent research efforts focus on improving the efficiency of ELF/VLF wave generation. One method to do so involves the spatial mapping of modul...
BACKGROUND The present study examined whether the very low frequency (VLF) power of heart rate variability (HRV) is predictive of clinical prognosis in patients with congestive heart failure (CHF). METHOD AND RESULTS The study recruited 54 consecutive CHF patients with emergency admission because of exacerbation of pulmonary congestion. Holter monitoring was performed after improvement of pul...
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