Theoretical study of the excitation, spectral characteristics, and geometrical attenuation of regional seismic phases

Abstract We present a theoretical study of the generation and geometrical attenuation of regional crustal phases. We do this through the computation of seismograms in the epicentral distance range from 60 to 500 km. The geometrical attenuation of Lg waves with epicentral distance is of the form r−0.83. Pg wave amplitudes display a much stronger decay of the form r−1.5. The spectral density of the crustal transfer function for Pg waves is relatively flat for frequencies between 0.1 and 5 Hz while Lg wave spectra strongly fall off beyond 2 to 3 Hz. The excitation of Pg wave is insensitive to the depth of the source within the crust while the Lg amplitude is about 50 per cent higher for a source in the upper and middle crust than in the lower crust. The amplitudes of these two phases drastically decrease when the source is below the Moho. These results illustrate the important role of wave guide played by the crust for the propagation of Lg and Pg. We find that the geometrical attenuation of Pg and Lg waves is independent of source mechanisms. In the case of an explosion, the excitation of Pg is insensitive to the source depth. The Lg wave amplitude is small in comparison to Pg and Rayleigh waves and depends on the closeness of the source to an interface or to the free surface.

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Role of Man in Production and Social Systems Based on Digital Technologies

Sociology and Law ◽

10.35854/2219-6242-2020-1-6-13 ◽

2020 ◽

pp. 6-13

Author(s):

V. K. Potemkin

Keyword(s):

Theoretical Study ◽

Social Systems ◽

Digital Technologies ◽

Changing Role ◽

Consistent Approach ◽

Social Improvement

The article presents the results of a theoretical study of the influence processes of the developed digital technologies and the activities of enterprises and organizations on the changing role of man in labor and their social improvement. The necessity of a balanced and consistent approach to create conditions for the use of digital technologies in practical activities and determining the con- sequences not only in enterprises and organizations, but also in the conscious behavior and social realities of all workers, without exception, is substantiated. The main directions of the development of digital technologies are determined, involving the wide participation of workers in their use in enterprises and organizations.

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Role of baroclinic wave amplitude and transport variation in climate change. Final report

10.2172/582181 ◽

1998 ◽

Author(s):

B.F. Farrell

Keyword(s):

Climate Change ◽

Wave Amplitude ◽

Final Report ◽

Baroclinic Wave

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

Current Diabetes Reviews ◽

10.2174/1573399815666190405171907 ◽

2020 ◽

Vol 16 (2) ◽

pp. 148-155 ◽

Cited By ~ 1

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.

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The Role of La2O3 in Enhancement the Radiation Shielding Efficiency of the Tellurite Glasses: Monte-Carlo Simulation and Theoretical Study

Materials ◽

10.3390/ma14143913 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3913

Author(s):

Aljawhara H. Almuqrin ◽

Mohamed Hanfi ◽

K. G. Mahmoud ◽

M. I. Sayyed ◽

Hanan Al-Ghamdi ◽

...

Keyword(s):

Monte Carlo Simulation ◽

Theoretical Study ◽

Radiation Shielding ◽

Photon Flux ◽

Transmission Factor ◽

Tellurite Glasses ◽

Attenuation Coefficients ◽

Binary Glass ◽

Buildup Factors

The radiation shielding competence was examined for a binary glass system xLa2O3 + (1 − x) TeO2 where x = 5, 7, 10, 15, and 20 mol% using MCNP-5 code. The linear attenuation coefficients (LACs) of the glasses were evaluated, and it was found that LT20 glass has the greatest LAC, while LT5 had the least LAC. The transmission factor (TF) of the glasses was evaluated against thicknesses at various selected energies and was observed to greatly decrease with increasing thickness; for example, at 1.332 MeV, the TF of the LT5 glass decreased from 0.76 to 0.25 as the thickness increased from 1 to 5 cm. The equivalent atomic number (Zeq) of the glasses gradually increased with increasing photon energy above 0.1 MeV, with the maximum values observed at around 1 MeV. The buildup factors were determined to evaluate the accumulation of photon flux, and it was found that the maximum values for both can be seen at around 0.8 MeV. This research concluded that LT20 has the greatest potential in radiation shielding applications out of the investigated glasses due to the glass having the most desirable parameters.

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Role of (H2O)n (n = 2–3) Clusters on the HO2 + O3 Reaction: A Theoretical Study

The Journal of Physical Chemistry B ◽

10.1021/acs.jpcb.5b07691 ◽

2015 ◽

Vol 120 (8) ◽

pp. 1560-1568 ◽

Cited By ~ 17

Author(s):

Luís P. Viegas ◽

António J. C. Varandas

Keyword(s):

Theoretical Study

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Theoretical study on the role of cooperative solvent molecules in the neutral hydrolysis of ketene

Theoretical Chemistry Accounts ◽

10.1007/s00214-010-0738-2 ◽

2010 ◽

Vol 127 (5-6) ◽

pp. 493-506 ◽

Cited By ~ 13

Author(s):

Xiao-Peng Wu ◽

Xi-Guang Wei ◽

Xiao-Ming Sun ◽

Yi Ren ◽

Ning-Bew Wong ◽

...

Keyword(s):

Theoretical Study ◽

Solvent Molecules ◽

Hydrolysis Of

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Observation of gliding tremors from the Gulf of Guinea might help solve over 50 year old mystery

10.5194/egusphere-egu21-3447 ◽

2021 ◽

Author(s):

Charlotte Bruland ◽

Sarah Mader ◽

Céline Hadziioannou

Keyword(s):

Spectral Analysis ◽

Volcanic Activity ◽

Rayleigh Waves ◽

Spectral Characteristics ◽

Gulf Of Guinea ◽

Seismic Amplitude ◽

Long Period ◽

Amplitude Spectra ◽

Using Data ◽

Over Time

In the 1960's a peak in the seismic amplitude spectra around 26 s was discovered and detected on stations worldwide. The source was located in the Gulf of Guinea, with approximate coordinates (0,0), and was believed to be generated continuously. A source with similar spectral characteristics was discovered near the Vanuatu Islands, at nearly the antipodal location of the Gulf of Guinea source. Since it was located close to the volcanoes in Vanuatu, this source is commonly attributed to magmatic processes. The physical cause of the 26 s microseism, however, remains unclear.We investigate the source location and evolution of the 26 s microseim using data from permanent broadband stations in Germany, France and Algeria and temporary arrays in Morocco, Cameroon and Botswana for spectral analysis and 3-C beamforming to get closer to resolving the source mechanism responsible for this enigmatic signal. We find that the signal modulates over time and is not always detectable, but occasionally it becomes so energetic it can be observed on stations worldwide. Such a burst can last for hours or days. The signal is visible on stations globally approximately 30 percent of the time. Our beamforming analysis confirms that the source is located in the Gulf of Guinea, as shown in previous studies, and that the location is temporally stable. Whenever the signal is detectable, both Love and Rayleigh waves are generated. We discover a spectral glide effect associated with the bursts, that so far has not been reported in the literature.&#160;The spectral glides last for about two days and are observed on stations globally. Although at higher frequencies, very long period tremors and gliding tremors are also observed on volcanoes as Redoubt in Alaska and Arenal in Costa Rica, suggesting that the origin of the 26 s tremor is also volcanic. However, there is no reported volcanic activity in the area where the source appears to be located.&#160;

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