scholarly journals Mild poikilocapnic hypoxia increases very low frequency haemoglobin oxygenation oscillations in prefrontal cortex

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Agnieszka Gruszecka ◽  
Monika Waskow ◽  
Marta A. Malkiewicz ◽  
J. Patrick Neary ◽  
Jyotpal Singh ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Healthy Subjects ◽  
Right Hemisphere ◽  
Low Frequency ◽  
Cerebrospinal Fluid Dynamics ◽  
Frequency Range ◽  
Brain Response ◽  
Very Low Frequency ◽  
First Time ◽  
Insight Into

Abstract Background The aim of the study was to investigate the effect of mild cerebral hypoxia on haemoglobin oxygenation (HbO2), cerebrospinal fluid dynamics and cardiovascular physiology. To achieve this goal, four signals were recorded simultaneously: blood pressure, heart rate / electrocardiogram, HbO2 from right hemisphere and changes of subarachnoid space (SAS) width from left hemisphere. Signals were registered from 30 healthy, young participants (2 females and 28 males, body mass index = 24.5 ± 2.3 kg/m2, age 30.8 ± 13.4 years). Results We analysed the recorded signals using wavelet transform and phase coherence. We demonstrated for the first time that in healthy subjects exposed to mild poikilokapnic hypoxia there were increases in very low frequency HbO2 oscillations (< 0.052 Hz) in prefrontal cortex. Additionally, SAS fluctuation diminished in the whole frequency range which could be explained by brain oedema. Conclusions Consequently the study provides insight into mechanisms governing brain response to a mild hypoxic challenge. Our study supports the notion that HbO2 and SAS width monitoring might be beneficial for patients with acute lung disease.

scholarly journals Mild Poikilocapnic Hypoxia Increases Very Low Frequency Haemoglobin Oxygenation Oscillations in Prefrontal Cortex

2021 ◽  
Author(s):  
Agnieszka Gruszecka ◽  
Monika Waskow ◽  
Marta A. Malkiewicz ◽  
J. Patrick Neary ◽  
Jyotpal Singh ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Healthy Subjects ◽  
Right Hemisphere ◽  
Low Frequency ◽  
Cerebrospinal Fluid Dynamics ◽  
Frequency Range ◽  
Brain Response ◽  
Very Low Frequency ◽  
First Time ◽  
Insight Into

Abstract The aim of the study was to investigate the effect of mild cerebral hypoxia on haemoglobin oxygenation (HbO2), cerebrospinal fluid dynamics and cardiovascular physiology. To achieve this goal, four signals were recorded simultaneously: blood pressure, ECG, HbO2 from right hemisphere and changes of SAS width from left hemisphere. Signals were registered from 30 healthy, young participants (2 females and 28 males, BMI = 24.5 ± 2.3 kg/m2, age 30.8 ± 13.4 years). We analysed the recorded signals using wavelet transform (WT). We demonstrated for the first time that in healthy subjects exposed to mild poikilokapnic hypoxia that there were increases in very low frequency HbO2 oscillations (< 0.052 Hz) in prefrontal cortex. Additionally, SAS fluctuation diminishes in the whole frequency range which could be explained by brain oedema. Consequently the study provides insight into mechanisms governing brain response to a mild hypoxic challenge. Our study supports the notion that HbO2 and SAS width monitoring might be beneficial for patients with acute lung disease, including SARS-CoV-2.

scholarly journals A census of the pulsar population observed with the international LOFAR station FR606 at low frequencies (25–80 MHz)

2020 ◽  
Vol 635 ◽  
pp. A76 ◽  
Author(s):  
L. Bondonneau ◽  
J.-M. Grießmeier ◽  
G. Theureau ◽  
A. V. Bilous ◽  
V. I. Kondratiev ◽  
...  
Keyword(s):  
Low Frequency ◽  
Frequency Range ◽  
Radio Pulsars ◽  
Low Frequencies ◽  
Radio Observatory ◽  
Future Studies ◽  
New Information ◽  
Upper Limits ◽  
Widespread Phenomenon ◽  
First Time

Context. To date, only 69 pulsars have been identified with a detected pulsed radio emission below 100 MHz. A LOFAR-core LBA census and a dedicated campaign with the Nançay LOFAR station in stand-alone mode were carried out in the years 2014–2017 in order to extend the known population in this frequency range. Aims. In this paper, we aim to extend the sample of known radio pulsars at low frequencies and to produce a catalogue in the frequency range of 25–80 MHz. This will allow future studies to probe the local Galactic pulsar population, in addition to helping explain their emission mechanism, better characterising the low-frequency turnover in their spectra, and obtaining new information about the interstellar medium through the study of dispersion, scattering, and scintillation. Methods. We observed 102 pulsars that are known to emit radio pulses below 200 MHz and with declination above −30°. We used the Low Band Antennas (LBA) of the LOw Frequency ARray (LOFAR) international station FR606 at the Nançay Radio Observatory in stand-alone mode, recording data between 25 and 80 MHz. Results. Out of our sample of 102 pulsars, we detected 64. We confirmed the existence of ten pulsars detected below 100 MHz by the LOFAR LBA census for the first time (Bilous et al. 2020, A&A, 635, A75) and we added two more pulsars that had never before been detected in this frequency range. We provided average pulse profiles, DM values, and mean flux densities (or upper limits in the case of non-detections). The comparison with previously published results allows us to identify a hitherto unknown spectral turnover for five pulsars, confirming the expectation that spectral turnovers are a widespread phenomenon.

scholarly journals Acoustic signalling during courtship in the painted goby, Pomatoschistus pictus

2007 ◽  
Vol 87 (4) ◽  
pp. 1017-1023 ◽  
Author(s):  
M.C.P. Amorim ◽  
A.S.M. Neves
Keyword(s):  
Low Frequency ◽  
Courtship Behaviour ◽  
Male Size ◽  
Pulse Trains ◽  
Very Low Frequency ◽  
Somatic Condition ◽  
In Captivity ◽  
First Time ◽  
Courtship Displays

Gobies emit sounds during different stages of reproduction, including courtship, pre-spawning events (in the nest) and spawning. The breeding sounds of the painted goby Pomatoschistus pictus and associated courtship behaviour were recorded in captivity and described for the first time. Males emitted thump-like sounds mainly when displaying alone in the nest and produced drumming sounds outside the nest. Thumps have never been reported for other species of the genus Pomatoschistus. Thumps were short (~80 ms) very-low frequency (below 100 Hz) non-pulsed sounds, whereas drums were longer (hundreds of ms) and consisted of low frequency (~300 Hz) pulse trains. Thump characteristics varied significantly among males but also showed high within-male variability. The frequency of thump emissions and courtship behaviour (total number of courtship displays, lead and nest display) were positively correlated with male size but not with male somatic condition. Thump bursts emitted during nest displays were significantly longer than when emitted with other behaviours. These results suggest that larger males courted females more intensively, both with visual and acoustic displays, than smaller ones.

Extremely low frequency detection of electrical discharges at Minamidake crater (Sakurajima volcano, Japan)

2020 ◽  
Author(s):  
Caron E.J. Vossen ◽  
Corrado Cimarelli ◽  
Alec J. Bennett ◽  
André Geisler ◽  
Damien Gaudin ◽  
...  
Keyword(s):  
Low Frequency ◽  
Japan Meteorological Agency ◽  
Frequency Range ◽  
Electrical Discharges ◽  
Very Low Frequency ◽  
Extremely Low Frequency ◽  
Sakurajima Volcano ◽  
Frequency Detection ◽  
The World ◽  
Active Volcanoes

&lt;p&gt;Volcanoes are increasingly better monitored around the world. Nonetheless, the detection and monitoring of volcanic ash plumes remains difficult, especially in remote areas. Intense electrical activity and lightning in volcanic plumes suggests that electrical monitoring of active volcanoes can aid the detection of ash emissions in near real-time. Current very low frequency and wide-band thunderstorm networks have proven to be able to detect plumes of large magnitude. However, the time delay and the relatively high number of non-detected explosive episodes show that the applicability of these systems to the detection of smaller (and often more frequent) ash-rich explosive events is limited. Here we use a different type of thunderstorm detector to observe electrical discharges generated by the persistent Vulcanian activity of Minamidake crater at Sakurajima volcano in Japan. The sensors consist of two antennas that measure the induced current due to the change in electric field with time. In contrast to the current thunderstorm networks, these sensors measure within the extremely low frequency range (1-45 Hz) and can detect lightning up to 35 kilometres distance.&lt;/p&gt;&lt;p&gt;Two detectors were installed at a distance of 3 and 4 kilometres from Minamidake crater and recorded almost continuously since July 2018. Within this period, the ash plumes reached a maximum height of 5.5 kilometres above the crater rim. Using a volcanic lightning detection algorithm and the catalogue of volcanic explosions compiled by the Japan Meteorological Agency (JMA), the number of electrical discharges was determined for each individual explosive event. In addition, the start of electrical discharges was compared to the eruption onset estimated by the JMA.&lt;/p&gt;&lt;p&gt;Preliminary results show that the detector closest to the crater had the highest detection efficiency. It detected electrical discharges during 60% of the eruptions listed by the JMA. This is significantly higher than for the World Wide Lightning Location Network, which detected electrical discharges (in the very low frequency range) within 20 kilometres of Sakurajima for less than 0.005% of the eruptions. Furthermore, the results show that for 40% of the detected eruptions, electrical discharges were detected before the estimated JMA timing. Hence, electrical discharges can mark the inception of the explosion with a higher precision and are an indication of ash emission. This demonstrates the value of the cost-effective sensors used here as a monitoring tool at active volcanoes.&lt;/p&gt;

scholarly journals Dynamic cerebral autoregulation during passive heat stress in humans

2009 ◽  
Vol 296 (5) ◽  
pp. R1598-R1605 ◽  
Author(s):  
David A. Low ◽  
Jonathan E. Wingo ◽  
David M. Keller ◽  
Scott L. Davis ◽  
Jian Cui ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heat Stress ◽  
Transfer Function ◽  
High Frequency ◽  
Cerebral Autoregulation ◽  
Low Frequency ◽  
Passive Heating ◽  
Frequency Range ◽  
Very Low Frequency ◽  
Dynamic Cerebral Autoregulation

This study tested the hypothesis that passive heating impairs cerebral autoregulation. Transfer function analyses of resting arterial blood pressure and middle cerebral artery blood velocity (MCA Vmean), as well as MCA Vmean and blood pressure responses to rapid deflation of previously inflated thigh cuffs, were examined in nine healthy subjects under normothermic and passive heat stress (increase core temperature 1.1 ± 0.2°C, P < 0.001) conditions. Passive heating reduced MCA Vmean [change (Δ) of 8 ± 8 cm/s, P = 0.01], while blood pressure was maintained (Δ −1 ± 4 mmHg, P = 0.36). Coherence was decreased in the very-low-frequency range during heat stress (0.57 ± 0.13 to 0.26 ± 0.10, P = 0.001), but was >0.5 and similar between normothermia and heat stress in the low- (0.07–0.20 Hz, P = 0.40) and high-frequency (0.20–0.35 Hz, P = 0.12) ranges. Transfer gain was reduced during heat stress in the very-low-frequency (0.88 ± 0.38 to 0.59 ± 0.19 cm·s−1·mmHg−1, P = 0.02) range, but was unaffected in the low- and high-frequency ranges. The magnitude of the decrease in blood pressure (normothermia: 20 ± 4 mmHg, heat stress: 19 ± 6 mmHg, P = 0.88) and MCA Vmean (13 ± 4 to 12 ± 6 cm/s, P = 0.59) in response to cuff deflation was not affected by the thermal condition. Similarly, the rate of regulation of cerebrovascular conductance (CBVC) after cuff release (0.44 ± 0.22 to 0.38 ± 0.13 ΔCBVC units/s, P = 0.16) and the time for MCA Vmean to recover to precuff deflation baseline (10.0 ± 7.9 to 8.7 ± 4.9 s, P = 0.77) were not affected by heat stress. Counter to the proposed hypothesis, similar rate of regulation responses suggests that heat stress does not impair the ability to control cerebral perfusion after a rapid reduction in perfusion pressure, while reduced transfer function gain and coherence in the very-low-frequency range during heat stress suggest that dynamic cerebral autoregulation is improved during spontaneous oscillations in blood pressure within this frequency range.

Effects of Very Low Frequency Tones on Auditory Thresholds

1966 ◽  
Vol 9 (1) ◽  
pp. 150-160 ◽  
Author(s):  
J. Jerger ◽  
B. Alford ◽  
A. Coats ◽  
B. French
Keyword(s):  
Adverse Effects ◽  
Sound Pressure ◽  
Human Subjects ◽  
Low Frequency ◽  
Pressure Level ◽  
Variable Speed ◽  
Frequency Range ◽  
Auditory Thresholds ◽  
Very Low Frequency ◽  
Piston Cylinder

Nineteen human subjects were exposed to repeated three-minute tones in the sound pressure level range from 119 to 144 dB and the frequency range from 2–22 cps. The tones were produced in an acoustic test booth by a piston-cylinder arrangement, driven by a variable speed direct current motor. Eight subjects showed no adverse effects. Temporary threshold shifts (TTS) of 10 to 22 dB in the frequency range from 3 000 to 8 000 cps were observed in the remaining 11 subjects. In addition, the 7 and 12 cps signals produced considerable masking over the frequency range from 100 to 4 000 cps.

scholarly journals Further genetic diversification in multiple tumors and an evolutionary perspective on therapeutics

2015 ◽  
Author(s):  
Yong Tao ◽  
Zheng Hu ◽  
Shaoping Ling ◽  
Shiou-Hwie Yeh ◽  
Weiwei Zhai ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Drug Resistance ◽  
Low Frequency ◽  
Frequency Range ◽  
Resistance Mutations ◽  
Primary Tumors ◽  
Very Low Frequency ◽  
Evolutionary Forces ◽  
Single Tumor ◽  
Multiple Hepatocellular Carcinoma

The genetic diversity within a single tumor can be extremely large, possibly with mutations at all coding sites (Ling et al. 2015). In this study, we analyzed 12 cases of multiple hepatocellular carcinoma (HCC) tumors by sequencing and genotyping several samples from each case. In 10 cases, tumors are clonally related by a process of cell migration and colonization. They permit a detailed analysis of the evolutionary forces (mutation, migration, drift and natural selection) that influence the genetic diversity both within and between tumors. In 23 inter-tumor comparisons, the descendant tumor usually shows a higher growth rate than the parent tumor. In contrast, neutral diversity dominates within-tumor observations such that adaptively growing clones are rarely found. The apparent adaptive evolution between tumors can be explained by the inherent bias for detecting larger tumors that have a growth advantage. Beyond these tumors are a far larger number of clones which, growing at a neutral rate and too small to see, can nevertheless be verified by molecular means. Given that the estimated genetic diversity is often very large, therapeutic strategies need to take into account the pre-existence of many drug-resistance mutations. Importantly, these mutations are expected to be in the very low frequency range in the primary tumors (and become frequent in the relapses, as is indeed reported (1-3). In conclusion, tumors may often harbor a very large number of mutations in the very low frequency range. This duality provides both a challenge and an opportunity for designing strategies against drug resistance (4-8).

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