scholarly journals Seismic and mechanical studies of the artificially triggered rockfall at Mount Néron (French Alps, December 2011)

2014 ◽  
Vol 14 (12) ◽  
pp. 3175-3193 ◽  
Author(s):  
P. Bottelin ◽  
D. Jongmans ◽  
D. Daudon ◽  
A. Mathy ◽  
A. Helmstetter ◽  
...  
Keyword(s):  
Low Frequency ◽  
Free Fall ◽  
Seismic Signal ◽  
Medium Size ◽  
Seismic Arrays ◽  
French Alps ◽  
Before And After ◽  
Remote Sensing Techniques ◽  
Two Phases ◽  
Element Technique

Abstract. The eastern limestone cliff of Mount Néron (French Alps) was the theater for two medium-size rockfalls between summer and winter 2011. On 14 August 2011, a ~2000 m3 rock compartment detached from the cliff, fell 100 m below and propagated down the slope. Although most of the fallen rocks deposited on the upper part of the slope, some blocks of about 15 m in size were stopped by a ditch and an earthen barrier after a run-out of 800 m. An unstable overhanging ~2600 m3 compartment remained attached to the cliff and was blasted on 13 December 2011. During this artificially triggered event, 7 blocks reached the same ditch, with volumes ranging from 0.8 to 12 m3. A semi-permanent seismic array located about 2.5 km from the site recorded the two events, providing a unique opportunity to understand and to compare the seismic phases generated during natural and artificially triggered rockfalls. Both events have signal duration of ~100 s with comparable maximum amplitudes recorded at large distances (computed local magnitude of 1.14 and 1.05, respectively), most of the energy lying below 20 Hz. Remote sensing techniques (photogrammetry and lidar) were employed before and after the provoked rockfall, allowing the volume and fracturing to be characterized. This event was filmed by two video cameras, and the generated ground motions were recorded using two temporary 3C seismic sensors and three seismic arrays deployed at the slope toe. Videos and seismogram processing provided estimates of the propagation velocity during the successive rockfall phases, which ranges from 12 to 30 m s−1. The main seismic phases were obtained from combined video and seismic signal analyses. The two most energetic phases are related to the ground impact of fallen material after free fall, and to individual rock block impacts into the ditch and the earthen barrier. These two phases are characterized by similar low-frequency content but show very different particle motions. The discrete element technique allowed reproducing the key features of the rockfall dynamics, yielding propagation velocities compatible with experimental observations.

scholarly journals Seismic and mechanical studies of the artificially triggered rockfall at the Mount Néron (French Alps, December 2011)

2014 ◽  
Vol 2 (2) ◽  
pp. 1505-1557 ◽  
Author(s):  
P. Bottelin ◽  
D. Jongmans ◽  
D. Daudon ◽  
A. Mathy ◽  
A. Helmstetter ◽  
...  
Keyword(s):  
Low Frequency ◽  
Free Fall ◽  
Seismic Signal ◽  
Medium Size ◽  
Seismic Arrays ◽  
French Alps ◽  
Before And After ◽  
Remote Sensing Techniques ◽  
Two Phases ◽  
Element Technique

Abstract. The eastern limestone cliff of Mount Néron (French Alps) was the theatre of two medium-size rockfalls between summer and winter 2011. On 14 August 2011, a ~ 2000 m3 rock compartment detached from the cliff, fell 100 m below and propagated down the slope. Although most of the fallen rocks deposited in the upper part of the slope, about 15 meter-size blocks were stopped by a ditch and an earthen barrier after a runout of 800 m. An unstable overhanging ~ 2600 m3 compartment remained attached to the cliff and was blasted on 13 December 2011. During this artificially triggered event, 7 blocks reached the same ditch, with volumes ranging from 0.8 to 12 m3. A semi-permanent seismic array located about 2.5 km from the site recorded the two events, providing a unique opportunity to understand and to compare the seismic phases generated during natural and artificially triggered rockfalls. Both events have signal duration of ~ 100 s with comparable maximum amplitudes recorded at large distances (computed local magnitude of 1.14 and 1.05, respectively), most of the energy lying below 20 Hz. Remote sensing techniques (photogrammetry and LiDAR) were employed before and after the provoked rockfall, allowing the volume and fracturing to be characterized. This event was filmed by two video cameras and the generated ground motions were recorded using two temporary 3C seismic sensors and 3 seismic arrays deployed at the slope toe. Movie and seismogram processing provided estimates of the propagation velocity during the successive rockfall phases, which ranges from 12 m s−1 to 30 m s−1. The main seismic phases were obtained from combined video and seismic signal analyses. The two most energetic phases are related to the ground impact of fallen material after free-fall, and to individual rock block impacts into the ditch and the earthen barrier. These two phases are characterized by similar low-frequency content but show very different particle motions. The discrete element technique allowed reproducing the key features of the rockfall dynamics, yielding propagation velocities compatible with experimental observations.

Study of Possible Relation between Fasting Plasma Glucagon, Gestational Diabetes and Development of Type 2 DM

2020 ◽  
Vol 16 (2) ◽  
pp. 148-155 ◽  
Author(s):  
Ashraf Okba ◽  
Salwa Seddik Hosny ◽  
Alyaa Elsherbeny ◽  
Manal Mohsin Kamal
Keyword(s):  
Gestational Diabetes ◽  
Pregnant Women ◽  
Post Partum ◽  
Plasma Glucagon ◽  
Type 2 Dm ◽  
Fasting Plasma ◽  
Before And After ◽  
Two Phases

Background and Aims: Women who develop GDM (gestational diabetes mellitus) have a relative insulin secretion deficiency, the severity of which may be predictive for later development of diabetes. This study aimed to investigate the role of fasting plasma glucagon in the prediction of later development of diabetes in pregnant women with GDM. Materials and Methods: The study was conducted on 150 pregnant women with GDM after giving informed oral and written consents and being approved by the research ethical committee according to the declaration of Helsinki. The study was conducted in two phases, first phase during pregnancy and the second one was 6 months post-partum, as we measured fasting plasma glucagon before and after delivery together with fasting and 2 hour post-prandial plasma sugar. Results: Our findings suggested that glucagon levels significantly increased after delivery in the majority 14/25 (56%) of GDM women who developed type 2 DM within 6 months after delivery compared to 6/20 (30%) patients with impaired fasting plasma glucose (IFG) and only 22/105 (20%) non DM women, as the median glucagon levels were 80,76, 55, respectively. Also, there was a high statistical difference between fasting plasma glucagon post-delivery among diabetic and non-diabetic women (p ≤ 0.001). These results indicated the useful role of assessing fasting plasma glucagon before and after delivery in patients with GDM to predict the possibility of type 2 DM. Conclusion: There is a relatively high glucagon level in GDM patients, which is a significant pathogenic factor in the incidence of subsequent diabetes in women with a history of GDM. This could be important in the design of follow-up programs for women with previous GDM.

Effects of activation frequency and force on low-frequency fatigue in human skeletal muscle

1999 ◽  
Vol 86 (4) ◽  
pp. 1337-1346 ◽  
Author(s):  
Stuart A. Binder-Macleod ◽  
David W. Russ
Keyword(s):  
Healthy Subjects ◽  
Human Skeletal Muscle ◽  
Low Frequency ◽  
Variable Frequency ◽  
Activation Pattern ◽  
Constant Frequency ◽  
Mean Frequency ◽  
Before And After ◽  
Low Frequency Fatigue ◽  
Force Time

No comparison of the amount of low-frequency fatigue (LFF) produced by different activation frequencies exists, although frequencies ranging from 10 to 100 Hz have been used to induce LFF. The quadriceps femoris of 11 healthy subjects were tested in 5 separate sessions. In each session, the force-generating ability of the muscle was tested before and after fatigue and at 2, ∼13, and ∼38 min of recovery. Brief (6-pulse), constant-frequency trains of 9.1, 14.3, 33.3, and 100 Hz and a 6-pulse, variable-frequency train with a mean frequency of 14.3 Hz were delivered at 1 train/s to induce fatigue. Immediately postfatigue, there was a significant effect of fatiguing protocol frequency. Muscles exhibited greater LFF after stimulation with the 9.1-, 14.3-, and variable-frequency trains. These three trains also produced the greatest mean force-time integrals during the fatigue test. At 2, ∼13, and ∼38 min of recovery, however, the LFF produced was independent of the fatiguing protocol frequency. The findings are consistent with theories suggesting two independent mechanisms behind LFF and may help identify the optimal activation pattern when functional electrical stimulation is used.

Effect of Incisions in the Brainstem Commissural Network on the Short-Term Vestibulo-Ocular Adaptation of the CAT

1991 ◽  
Vol 1 (3) ◽  
pp. 223-239
Author(s):  
G. Cheron
Keyword(s):  
Low Frequency ◽  
Adaptive Plasticity ◽  
Training Procedure ◽  
Optokinetic Response ◽  
Mean Values ◽  
Ocular Reflex ◽  
Optokinetic Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Vor Adaptation

This study was intended to test the adaptive plasticity of the vestibulo-ocular reflex before and after either a midsagittal or parasagittal incision in the brainstem. Eye movements were measured with the electromagnetic search coil technique during the vestibulo-ocular reflex (VORD) in the dark, the optokinetic reflex (OKN), and the visuo-vestibular adaptive training procedure. Two types of visual-vestibular combined stimulation were applied by means of low frequency stimuli (0.05 to 0.10 Hz). In order to increase or decrease the VORD gain, the optokinetic drum was oscillated either 180∘ out-of-phase or in-phase with the vestibular stimulus turntable. This “training” procedure was applied for 4 hours. Initial measurements of the VORD were normal with a mean gain value of 0.92 ± 0.08. After 4 hours of “training” with the out-of-phase condition (180∘), VORD gain reached mean values of 1.33 ± 0.11 (n = 6 cats). In the in-phase combination, the mean VORD gain decreased from 1.0 to 0.63 ± 0.02 (n = 2 cats). No significant change of VORD phase was found in any of the cats. Midsagittal or parasagittal pontomedullary brainstem incisions were performed in 4 cats. Recovery of the VOR was tested on the 2nd, 7th, and 30th day after operation. After the 30th day, recovery of the VORD gain stabilized at about 66% of the initial preoperative value. At this stage of the recovery, the optokinetic response (OKN) of the midsagittal-Iesioned cats was practically normal: in the parasagittal-Jesioned cats, the postoperative OKN responses were asymmetric. After stabilization of recovery, lesioned cats were trained with the same adaptation procedure. Although the direct effect of the visuo-vestibular combined stimulation during the training was still operative in all lesioned cats, the adaptive plasticity was completely abolished by the lesions. These results suggest that the commissural brainstem network may play a crucial role in the acquisition of the forced VOR adaptation.

Comparative study on effect of neutral spinal bath and neutral spinal spray on blood pressure, heart rate and heart rate variability in healthy volunteers

2018 ◽  
Vol 16 (2) ◽  
Author(s):  
Arundhati Goley ◽  
A. Mooventhan ◽  
NK. Manjunath
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Healthy Volunteers ◽  
Group Analysis ◽  
Low Frequency ◽  
Single Session ◽  
Arterial Blood ◽  
Before And After ◽  
Instantaneous Heart Rate

Abstract Background Hydrotherapeutic applications to the head and spine have shown to improve cardiovascular and autonomic functions. There is lack of study reporting the effect of either neutral spinal bath (NSB) or neutral spinal spray (NSS). Hence, the present study was conducted to evaluate and compare the effects of both NSB and NSS in healthy volunteers. Methods Thirty healthy subjects were recruited and randomized into either neutral spinal bath group (NSBG) or neutral spinal spray group (NSSG). A single session of NSB, NSS was given for 15 min to the NSBG and NSSG, respectively. Assessments were taken before and after the interventions. Results Results of this study showed a significant reduction in low-frequency (LF) to high-frequency (HF) (LF/HF) ratio of heart rate variability (HRV) spectrum in NSBG compared with NSSG (p=0.026). Within-group analysis of both NSBG and NSSG showed a significant increase in the mean of the intervals between adjacent QRS complexes or the instantaneous heart rate (HR) (RRI) (p=0.002; p=0.009, respectively), along with a significant reduction in HR (p=0.002; p=0.004, respectively). But, a significant reduction in systolic blood pressure (SBP) (p=0.037) and pulse pressure (PP) (p=0.017) was observed in NSSG, while a significant reduction in diastolic blood pressure (DBP) (p=0.008), mean arterial blood pressure (MAP) (p=0.008) and LF/HF ratio (p=0.041) was observed in NSBG. Conclusion Results of the study suggest that 15 min of both NSB and NSS might be effective in reducing HR and improving HRV. However, NSS is particularly effective in reducing SBP and PP, while NSB is particularly effective in reducing DBP and MAP along with improving sympathovagal balance in healthy volunteers.

Reversal of muscle fatigue during 16 h of heavy intermittent cycle exercise

2004 ◽  
Vol 97 (6) ◽  
pp. 2166-2175 ◽  
Author(s):  
H. J. Green ◽  
T. A. Duhamel ◽  
S. Ferth ◽  
G. P. Holloway ◽  
M. M. Thomas ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Muscle Fatigue ◽  
Intermittent Exercise ◽  
Low Frequency ◽  
Quadriceps Muscle ◽  
Stimulation Frequency ◽  
Peak Oxygen Consumption ◽  
Force Frequency ◽  
Reduction In Force ◽  
Before And After

This study examined the effects of extended sessions of heavy intermittent exercise on quadriceps muscle fatigue and weakness. Twelve untrained volunteers (10 men and 2 women), with a peak oxygen consumption of 44.3 ± 2.3 ml·kg−1·min−1, exercised at ∼91% peak oxygen consumption for 6 min once per hour for 16 h. Muscle isometric properties assessed before and after selected repetitions (R1, R2, R4, R7, R12, and R15) were used to quantitate fatigue (before vs. after repetitions) and weakness (before vs. before repetitions). Muscle fatigue at R1 was indicated by reductions ( P < 0.05) in peak twitch force (135 ± 13 vs. 106 ± 11 N) and by a reduction ( P < 0.05) in the force-frequency response, which ranged between ∼53% at 10 Hz (113 ± 12 vs. 52.6 ± 7.4 N) and ∼17% at 50 Hz (324 ± 27 vs. 270 ± 30 N). No recovery of force, regardless of stimulation frequency, was observed during the 54 min between R1 and R2. At R2 and for all subsequent repetitions, no reduction in force, regardless of stimulation frequency, was generally found after the exercise. The only exception was for R2, where, at 20 Hz, force was reduced ( P < 0.05) by 18%. At R15, force before repetitions for high frequencies (i.e., 100 Hz) returned to R1 (333 ± 29 vs. 324 ± 27 N), whereas force at low frequency (i.e., 10 Hz) was only partially ( P < 0.05) recovered (113 ± 12 vs. 70 ± 6.6 N). It is concluded that multiple sessions of heavy exercise can reverse the fatigue noted early and reduce or eliminate weakness depending on the frequency of stimulation.

Near-maximal voluntary hyperpnea and ventilatory muscle function

1984 ◽  
Vol 57 (6) ◽  
pp. 1742-1748 ◽  
Author(s):  
T. R. Bai ◽  
B. J. Rabinovitch ◽  
R. L. Pardy
Keyword(s):  
Muscle Function ◽  
Low Frequency ◽  
Normal Subjects ◽  
Pressure Time ◽  
Before And After ◽  
Expiratory Muscles ◽  
Four Levels ◽  
Frequency Relationship ◽  
Low Frequency Power ◽  
Relationship Of

Because of its potential relevance to heavy exercise we studied the ventilatory muscle function of five normal subjects before, during, and after shortterm near-maximal voluntary normocapnic hyperpnea. Measurements of pleural and abdominal pressures and diaphragm electromyogram (EMG) during hyperpnea and of maximum respiratory pressures before and after hyperpnea were made at four levels of ventilation: 76, 79, and 86% maximal voluntary ventilation (MVV) and at MVV. Measurements of pleural and abdominal pressures and diaphragm electromyogram (EMG) during hyperpnea and of maximum respiratory pressures before and after hyperpnea were made. The pressure-stimulation frequency relationship of the diaphragm obtained by unilateral transcutaneous phrenic nerve stimulation was studied in two subjects before and after hyperpnea. Decreases in maximal inspiratory (PImax) and transdiaphragmatic (Pdimax) strength were recorded posthyperpnea at 76 and 79% MVV. Decreases in the pressure-frequency curves of the diaphragm and the ratio of high-to-low frequency power of the diaphragm EMG occurred in association with decreases in Pdimax. Analysis of the pressure-time product (P X dt) for the inspiratory and expiratory muscles individually indicated the increasing contribution of expiratory muscle force to the attainment of higher levels of ventilation. Demonstrable ventilatory muscle fatigue may limit endurance at high levels of ventilation.

scholarly journals The Effect of 12 Hz Extremely Low-Frequency Electromagnetic Fields on Visual Memory of Male Macaque Monkeys

2021 ◽  
Author(s):  
Masoomeh Kazemi ◽  
◽  
Hamed Aliyari ◽  
Elaheh Tekieh ◽  
Hassan Tavacoli ◽  
...  
Keyword(s):  
Electromagnetic Fields ◽  
Visual Memory ◽  
Rhesus Macaques ◽  
Low Frequency ◽  
Serum Levels ◽  
Control Group ◽  
Behavioral Tests ◽  
Extremely Low Frequency ◽  
Before And After ◽  
Male Rhesus

Introduction: Today, humans leave in a world surrounded by electromagnetic fields. Numerous studies have been carried out to discover the biological, physiological, and behavioral effects of electromagnetic fields on humans and animals. Given the biological similarities between monkeys and humans, the goal of the present research was to examine Visual Memory (VM), hormonal, genomic, and anatomic changes, and changes of the amygdala function in the male rhesus macaques who exposed to extremely low-frequency magnetic fields (ELF/MF). Materials and methods: Four male Rhesus Macaques (Macaca mulatta) were used. For the behavioral tests the animals were needed to be fasting for 17 hours, and for the behavioral tests such as visual memory, cooperation of the animal was necessary. Using the radiation protocol, two of the monkeys were exposed to 12-Hz electromagnetic fields with a magnitude of 0.7 microtesla (electromagnetic radiation) four hours a day for a month. Before and after the exposure, a visual memory test was conducted using a coated device (visible reward) on a movable stand. Ten mL of blood was obtained from the femoral artery of the monkeys and half of it was used to examine cortisol serum levels using MyBioSource kits (made in the USA). The other half of blood samples were used to extract lymphocytes for assaying expressions of Glucocorticoid Receptor (GR) genes before and after radiation using the PCR method. Anatomic studies of the amygdala were carried out based on pre- and post-radiation Magnetic Resonance Imaging (MRI). Findings: Research results indicated that visual memory in male primates increased significantly at the 12Hz frequency. Hormonal analysis at the 12Hz frequency showed a decrease in cortisol serum levels. However, visual memory and serum cortisol levels did not change considerably in male primates in the control group. There was no considerable amygdala volumetric difference at the 12 Hz frequency. The expression of the GR genes decreased at 12Hz compared to the control group. Conclusion: In short, these results indicated that ELF may have a beneficial value for memory enhancement as indicated by the fact that exposure to the 12 HZ ELF can enhance visual memory. This may be due to a decrease in plasma cortisol, and/or expression of GR genes. Moreover, direct involvement of the amygdala in this regard cannot be recommended.

scholarly journals Towards a third phase of regulation:

2016 ◽  
Author(s):  
Julie Berg ◽  
Jean-Pierre Nouveau
Keyword(s):  
South Africa ◽  
Private Security ◽  
State Regulation ◽  
Good Time ◽  
Security Industry ◽  
Third Phase ◽  
Regulatory Systems ◽  
Before And After ◽  
Two Phases ◽  
Legislative Review

With the legislative review of police oversight currently taking place in South Africa, now is a good time to reflect on the regulation of the private security industry. This article does so by focusing on three challenges to the current private security regulatory systems: the increased pluralisation of policing within public spaces; the operation of hidden sectors within the industry; and the nature of criminal abuses perpetuated by the industry. We do this to demonstrate the need for a re-imagining of what regulation, especially state regulation, of this industry should entail. The aim of the article is not to review the current legislation or to identify gaps and propose means of filling those gaps, but rather to reflect on the underlying premises informing the legislation and propose a shift in thinking. We do this by briefly identifying two phases of state regulation in South Africa, implemented before and after the change to a new democratic dispensation, and suggest that we are now entering a third phase of regulation. We conclude with suggestions as to what this third phase may entail.

scholarly journals Effectiveness of Extremely Low Frequency Electromagnetic Field and Pulsed Low-Level Laser Therapy in Acute Stroke Treatment

2020 ◽  
Vol 7 (3) ◽  
pp. 127-131
Author(s):  
Farzad Ashrafi ◽  
Amir Rezaei ◽  
Arash Azhideh ◽  
Faraj Tabeie ◽  
Latif Gachkar ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Medical Condition ◽  
Low Frequency ◽  
Cognitive Status ◽  
Low Level Laser Therapy ◽  
Stroke Treatment ◽  
Extremely Low Frequency ◽  
Level Laser ◽  
Significant Difference ◽  
Before And After

Introduction: Stroke is one of the most devastating neurologic conditions in the world. Despite all the efforts that have been made for effective treatment, the prevalence of this medical condition is still high. One of the new methods in the treatment of patients is the use of low power laser and pulsed magnetic fields. The previous studies investigated the effectiveness of these methods individually. However, the present study aimed to investigate their effectiveness in combination. Methods: We divided the patients into control (n=26) and experimental (n=26) groups. The primary variables included the Mini-Mental State Examination (MMSE) and the National Institute of Health Stroke Scale (NIHSS). The experimental group received extremely low-frequency electromagnetic field (EMF-ELF) treatment with 1 mT power and laser in rejection with a wavelength of 840 nm for 5 days and 45 min/d. Results: The variable measured during this study, in addition to comparing the results of the intervention between the control and experimental groups, showed a significant difference in all indicators before and after the intervention. The mean and standard deviations of the modified Rankin scale (mRS), functional status (Barthel’s index), and cognitive status (MMSE) (P<0.001) were signed between 2 groups. Conclusion: Laser and magnetic field combination can be effective in the treatment of stroke. Further studies are recommended to ensure a better comparison.

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