DETERMINATION OF THE PARAMETERS OF CANCELLOUS BONE USING LOW FREQUENCY ACOUSTIC MEASUREMENTS

2004 ◽  
Vol 12 (02) ◽  
pp. 99-126 ◽  
Author(s):  
JAMES L. BUCHANAN ◽  
ROBERT P. GILBERT ◽  
KHALDOUN KHASHANAH
Keyword(s):  
Cancellous Bone ◽  
Low Frequency ◽  
Acoustic Measurements ◽  
Biot Model ◽  
Poroelastic Media ◽  
High Degree

The Biot model is widely used to model poroelastic media. Several authors have studied its applicability to cancellous bone. In this article the feasibility of determining the Biot parameters of cancellous bone by acoustic interrogation using frequencies in the 5–15 kHz range is studied. It is found that the porosity of the specimen can be determined with a high degree of accuracy. The degree to which other parameters can be determined accurately depends upon porosity.

scholarly journals DETERMINATION OF THE PARAMETERS OF CANCELLOUS BONE USING HIGH FREQUENCY ACOUSTIC MEASUREMENTS II: INVERSE PROBLEMS

2007 ◽  
Vol 15 (02) ◽  
pp. 199-220 ◽  
Author(s):  
JAMES L. BUCHANAN ◽  
ROBERT P. GILBERT
Keyword(s):  
Cancellous Bone ◽  
High Frequency ◽  
Acoustic Pressure ◽  
Measured Data ◽  
Acoustic Measurements ◽  
Biot Model ◽  
Parameter Recovery ◽  
Recovery Algorithm ◽  
Poroelastic Media

In a precursor to this article the Biot model was used to model poroelastic media. The question this article addresses is whether the sort of experiments described by McKelvie and Palmer, Williams, and Hosokawa and Otani can be used to determine the parameters of the Biot model. A method of computing acoustic pressure in the low 100 kHz range was developed in Buchanan and Gilbert, "Determination of the parameters of cancellous bone using high frequency acoustic measurements," which appeared in Math. Comput. Modelling. In the present work a parameter recovery algorithm which uses parallel processing is developed and tested. It is found that when it is assumed that the agreement between calculated and measured data is about two digits, porosity can be determined to within about 1–2% and permeability, pore size and the bulk moduli to within about 40%, but in most cases less than 20%.

Determination of cancellous bone density using low frequency acoustic measurements

2008 ◽  
Vol 87 (10-11) ◽  
pp. 1213-1225 ◽  
Author(s):  
Robert P. Gilbert ◽  
Philippe Guyenne ◽  
George C. Hsiao
Keyword(s):  
Bone Density ◽  
Cancellous Bone ◽  
Low Frequency ◽  
Acoustic Measurements

scholarly journals High-degree gravity modes in the single sdB star HD 4539

2019 ◽  
Vol 489 (4) ◽  
pp. 4791-4801 ◽  
Author(s):  
R Silvotti ◽  
M Uzundag ◽  
A S Baran ◽  
R H Østensen ◽  
J H Telting ◽  
...  
Keyword(s):  
Large Fraction ◽  
Amplitude Spectrum ◽  
Rotation Period ◽  
Low Frequency ◽  
Surface Layers ◽  
Robust Identification ◽  
Robust Detection ◽  
Orbital Periods ◽  
High Degree

ABSTRACT HD 4539 (alias PG 0044 + 097 or EPIC 220641886) is a bright (V  = 10.2) long-period V1093 Her-type subdwarf B (sdB) pulsating star that was observed by the Kepler spacecraft in its secondary (K2) mission. We use the K2 light curve (78.7 d) to extract 169 pulsation frequencies, 124 with a robust detection. Most of these frequencies are found in the low-frequency region typical of gravity (g-)modes, but some higher frequencies corresponding to pressure (p-)modes are also detected. Therefore HD 4539 is a hybrid pulsator and both the deep and surface layers of the star can potentially be probed through asteroseismology. The lack of any frequency splitting in its amplitude spectrum suggests that HD 4539 has a rotation period longer than the K2 run and/or that it is seen pole-on. From asymptotic period spacing we see many high-degree modes, up to l  = 12, in the spectrum of HD 4539, with amplitudes as low as a few ppm. A large fraction of these modes can be identified and for ∼29 per cent of them we obtain a unique and robust identification corresponding to l ≤ 8. Our study includes also a new determination of the atmospheric parameters of the star. From low-resolution spectroscopy we obtain Teff  = 22 800 ± 160 K, log g  = 5.20 ± 0.02, and log(N(He)/N(H))  = −2.34 ± 0.05. By fitting the SED we obtain Teff  = 23 470$^{+650}_{-210}$ K, R⋆  = 0.26 ± 0.01 R⊙, and M⋆  = 0.40 ± 0.08 M⊙. Moreover, from 11 high-resolution spectra we see the radial velocity variations caused by the stellar pulsations, with amplitudes of ≈150 m s−1 for the main modes, and we can exclude the presence of a companion with a minimum mass higher than a few Jupiter masses for orbital periods below ∼300 d.

Feasibility of Molecular Structure Determination With a High Resolution Electron Microscope

1968 ◽  
Vol 26 ◽  
pp. 338-339
Author(s):  
T. A. Welton
Keyword(s):  
Electron Microscope ◽  
Substrate Surface ◽  
Helical Axis ◽  
Base Plane ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
High Degree ◽  
Degree Of Order ◽  
Purine Pyrimidine

An ultimate design goal for an improved electron microscope, aimed at biological applications, is the determination of the structure of complex bio-molecules. As a prototype of this class of problems, we propose to examine the possibility of reading DNA sequence by an imaginable instrument design. This problem ideally combines absolute importance and relative simplicity, in as much as the problem of enzyme structure seems to be a much more difficult one.The proposed technique involves the deposition on a thin graphite lamina of intact double helical DNA rods. If the structure can be maintained under vacuum conditions, we can then make use of the high degree of order to greatly reduce the work involved in discriminating between the four possible purine-pyrimidine arrangements in each base plane. The phosphorus atoms of the back bone form in projection (the helical axis being necessarily parallel to the substrate surface) two intertwined sinusoids. If these phosphorus atoms have been located up to a certain point on the molecule, we have available excellent information on the orientation of the base plane at that point, and can then locate in projection the key atoms for discrimination of the four alternatives.

scholarly journals Influence of the Share of Renewable Energy Sources on the Level of Energy Security in EECCA Countries

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 903 ◽  
Author(s):  
Ivan Trifonov ◽  
Dmitry Trukhan ◽  
Yury Koshlich ◽  
Valeriy Prasolov ◽  
Beata Ślusarczyk
Keyword(s):  
Renewable Energy ◽  
Energy Security ◽  
Structural Characteristics ◽  
Renewable Energy Sources ◽  
Energy Resource ◽  
Energy Sources ◽  
Structural Content ◽  
High Degree

In this study we aimed to determine the extent to which changes in the share of renewable energy sources, their structural complex, and the level of energy security in Eastern Europe, Caucasus and Central Asia (EECCA) countries in the medium- and long-term are interconnected. The study was performed through modeling and determination of the structural characteristics of energy security in the countries. The methodology of the approach to modeling was based on solving the problem of nonlinear optimization by selecting a certain scenario. For the study, the data of EECCA countries were used. The ability of EECCA countries to benefit from long-term indirect and induced advantages of the transformation period depends on the extent to which their domestic supply chains facilitate the deployment of energy transformation and induced economic activity. This study provides an opportunity to assess the degree of influence of renewable energy sources on the level of energy security of countries in the context of energy resource diversification. The high degree of influence of renewable energy sources on energy security in the EECCA countries has been proven in the implementation of the developed scenarios for its increase. Energy security is growing. At the same time, its level depends not only on an increase in the share of renewable sources but also on the structure of energy resources complex of countries, and the development of various renewable energy sources. Therefore, today the EECCA countries are forced not only to increase the share of renewable energy sources but also to attach strategic importance to the structural content of their energy complex.

Resistance to Outflow of Cerebrospinal Fluid Determined by Bolus Injection Technique and Constant Rate Steady State Infusion in Humans

Neurosurgery ◽  
1985 ◽  
Vol 16 (3) ◽  
pp. 336-340 ◽  
Author(s):  
Michael Kosteljanetz
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Bolus Injection ◽  
Point Of View ◽  
Injection Technique ◽  
Communicating Hydrocephalus ◽  
Constant Rate ◽  
High Degree ◽  
Infusion Technique

Abstract Two methods for the determination of resistance to the outflow of cerebrospinal fluid, the bolus injection technique and the constant rate steady state infusion technique, were compared. Thirty-two patients with a variety of intracranial diseases (usually communicating hydrocephalus) were studied. There was a high degree of correlation between the resistance values obtained with the two methods, but values based on the bolus injection technique were systematically and statistically significantly lower than those obtained with the constant rate infusion test. From a practical point of view. both methods were found to be applicable in a clinical setting.

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