scholarly journals Electro–magneto-encephalography for a three-shell model: distributed current in arbitrary, spherical and ellipsoidal geometries

2008 ◽  
Vol 6 (34) ◽  
pp. 479-488 ◽  
Author(s):  
A.S Fokas
Keyword(s):  
Shell Model ◽  
A Priori ◽  
Arbitrary Geometry ◽  
The Third ◽  
Complete Determination ◽  
Simultaneous Use ◽  
Neuronal Current ◽  
The Brain ◽  
Three Components

The problem of determining a continuously distributed neuronal current inside the brain under the assumption of a three-shell model is analysed. It is shown that for an arbitrary geometry, electroencephalography (EEG) provides information about one of the three functions specifying the three components of the current, whereas magnetoencephalography (MEG) provides information about a combination of this function and of one of the remaining two functions. Hence, the simultaneous use of EEG and MEG yields information about two of the three functions needed for the reconstruction of the current. In particular, for spherical and ellipsoidal geometries, it is possible to determine the angular parts of these two functions as well as to obtain an explicit constraint satisfied by their radial parts. The complete determination of the radial parts, as well as the determination of the third function, requires some additional a priori assumption about the current. One such assumption involving harmonicity is briefly discussed.

Which Part of the Neuronal Current can be Determined by Electroencephalography?

2020 ◽  
pp. 66-80
Author(s):  
A. S. Fokas ◽  
Parham Hashemzadeh ◽  
Richard M. Leahy
Keyword(s):  
Cerebral Cortex ◽  
Shell Model ◽  
Numerical Procedure ◽  
Scalar Function ◽  
Ellipsoidal Model ◽  
Neuronal Current ◽  
The Brain ◽  
Primary Current

This chapter considers the so-called four-shell model of the brain and assumes that a continuously distributed primary neuronal current is supported either within the cerebral cortex or only on the surface of the cortex, S c, and is normal to this surface. The authors show that in the former case, electroencephalogram recordings are affected only by the value of the irrotational part of the current denoted by the scalar function Ψ‎(τ‎) and by the gradient of Ψ‎(τ‎) on S c. An effective numerical procedure for reconstructing Ψ‎(τ‎) in the particular case of an ellipsoidal model is discussed. If the primary current is supported on S c, and it is normal to it, then it can be reconstructed uniquely.

scholarly journals IV. On the determination of the terms in the disturbing function of the fourth order as regards the eccentricities and inclinations which give rise to secular inequali­ties

1835 ◽  
Vol 125 ◽  
pp. 57-81
Keyword(s):  
Fourth Order ◽  
A Priori ◽  
Disturbing Function ◽  
Left Hand ◽  
The Third ◽  
Hand Column ◽  
The Subject ◽  
Analytical Expressions

Hitherto in the theory of the secular inequalities the terms in the disturbing function of the fourth order as regards the inclinations have been neglected. As the magnitude of these terms depends, in great measure, upon certain numerical co­efficients, it is impossible to form any precise notion à priori with respect to their amount, and as to the error which may arise from neglecting them. I have therefore thought it desirable to ascertain their analytical expressions; and the details of this calculation form the subject of this paper. Some of the secular inequalities which result from these terms are far within the limits of accuracy which Laplace appears to have contemplated in the third volume of the Mécanique Céleste. The method which I have here adopted for developing the disturbing function rests upon principles which I have already explained. Very little trouble is requisite to obtain certain analytical expressions for the terms upon which the secular inequalities depend, or for any others, in the development of the disturbing function; but it is not so easy to put these expressions in the simplest form of which they are susceptible; and this is a point to which I think hitherto sufficient attention has not been paid. It will be found that I have obtained, finally, expressions of very remarkable sim­plicity; to accomplish this, however, I have been obliged to go through tedious pro­cesses of reduction, the details of which are here subjoined, in order that my results may be verified or corrected without difficulty. In order to give an additional example of the great facility with which terms in the disturbing function are arrived at by my method, I have calculated one of those given by Professor Airy, and which is required in the determination of his inequality of Venus; and I have arrived at the result which he has given. The same method, with certain modifications, is applicable to the de­velopment of the disturbing function in terms of the true longitudes. The terms in the disturbing function which give rise to the secular inequalities of the elliptic constants, when the terms of the order of the fourth powers of the eccentricities and inclinations are retained, and higher powers of those quantities are neglected, are as follows: and I propose, as they form, in fact, a system apart, to distinguish them by the indices given in the left-hand column.

The Number and the Kantian Research Program in Modern Neuroscience

2021 ◽  
pp. 50-60
Author(s):  
Valentin A. Bazhanov ◽  
Keyword(s):  
Research Program ◽  
A Priori ◽  
Early Age ◽  
Cultural Neuroscience ◽  
Activity Type ◽  
Mathematical Abilities ◽  
The Status ◽  
Systematic Development ◽  
The Brain

The article presents the attempt to consider the Kantian research program in modern neuroscience in its part, which relates to the representation of the “number” and the mechanisms for processing numerical information by neu­ral structures. We claim that Kantian ideas about the a priori nature of certain mathematical categories related to the status of space and time [geometry and arithmetic], which were subjected to doubt as a result of the discovery of non-Euclidean geometries, proved to be highly demanded and reassessed as a result of the intensive progress of modern cognitive and cultural neuroscience. The dis­covery of the subitizing phenomena, “sense of number” and “sense of place” (analogous to the navigation system of the brain) push us to recall the old Kan­tian judgments concerning certain a priori constructions of mathematics. The on­togenetic foundations of such phenomena, their conditionality by the features of the functioning of the brain, reveal not the metaphorical, but the strategic nature of the Kantian research program in modern neuroscience. In the context of these studies, it also turned out that in the case of living systems, one can speak about their proto-arithmetic traits, and in the case of humans, mathematical abilities that are largely independent of the language, and their systematic development from an early age significantly increases the likelihood of successful mathemati­cal activity in future. Attention drawn to the interdependence of the activity of the developing brain, social and cultural contexts, which intersects and expressed in the process of acculturation of the brain and vice versa – neural determination of culture. This kind of interaction support the idea of the possibility of expand­ing original Kantian idea and introducing the idea related to the transcendental­ism of the activity type

Investigations on skeletal growth zones via bone scans as base of determination of optimal time for surgery in mandibular asymmetry

2000 ◽  
Vol 39 (05) ◽  
pp. 121-126 ◽  
Author(s):  
R. Werz ◽  
P. Reuland
Keyword(s):  
Bone Growth ◽  
Region Of Interest ◽  
Tracer Uptake ◽  
Optimal Time ◽  
Mandibular Bone ◽  
The Third ◽  
Mandibular Asymmetry ◽  
Bone Scans ◽  
Epiphyseal Plates

Summary Aim of the study was to find out wether there is a common stop of growth of mandibular bone, so that no individual determination of the optimal time for surgery in patients with asymmetric mandibular bone growth is needed. As there are no epiphyseal plates in the mandibular bone, stop of growth cannot be determined on X-ray films. Methods: Bone scans of 731 patients [687 patients (324 male, 363 female) under 39 y for exact determination of end of growth and 44 (21 male, 23 female) patients over 40 y for evaluation of nongrowth dependant differences in tracer uptake] were reviewed for the study. All the patients were examined 3 hours after injection of 99mTc-DPD. Tracer uptake was measured by region of interest technique in different points of the mandibular bone and in several epiphyseal plates of extremities. Results: Tracer uptake in different epiphyseal plates of the extremities shows strong variation with age and good correlation with reported data of bone growth and closure of the epiphyseal plates. The relative maximum of bone activity is smaller in mandibular bone than in epiphyseal plates, which show well defined peaks, ending at 15-18 years in females and at 18-21 years in males. In contrast, mandibular bone shows no well defined end of growing but a gradually reduction of bone activity which remains higher than bone activity in epiphyseal plates over several years. Conclusion: No well defined end of growth of mandibular bone exists. The optimal age for surgery of asymmetric mandibular bone growth is not before the middle of the third decade of life, bone scans performed earlier for determination of bone growth can be omitted. Bone scans performed at the middle of the third decade of life help to optimize the time of surgical intervention.

THE FACTORS OF CAREER SELF-DETERMINATION OF STUDENTS OF HIGHER EDUCATION INSTITUTIONS

2019 ◽  
Vol 7 (1) ◽  
pp. 9-20
Author(s):  
Inna Yeung
Keyword(s):  
Higher Education ◽  
Higher Education Institutions ◽  
Well Being ◽  
Young Person ◽  
Self Determination ◽  
Full Time ◽  
Actual Problem ◽  
The Third ◽  
The Right

Choice of profession is a social phenomenon that every person has to face in life. Numerous studies convince us that not only the well-being of a person depends on the chosen work, but also his attitude to himself and life in general, therefore, the right and timely professional choice is very important. Research about factors of career self-determination of students of higher education institutions in Ukraine shows that self-determination is an important factor in the socialization of young person, and the factors that determine students' career choices become an actual problem of nowadays. The present study involved full-time and part-time students of Institute of Philology and Mass Communications of Open International University of Human Development "Ukraine" in order to examine the factors of career self-determination of students of higher education institutions (N=189). Diagnostic factors of career self-determination of students studying in the third and fourth year were carried out using the author's questionnaire. Processing of obtained data was carried out using the Excel 2010 program; factorial and comparative analysis were applied. Results of the study showed that initial stage of career self-determination falls down on the third and fourth studying year at the university, when an image of future career and career orientations begin to form. At the same time, the content of career self-determination in this period is contradictory and uncertain, therefore, the implementation of pedagogical support of this process among students is effective.

ADRENOCORTICAL FUNCTION IN PATIENTS WITH ACUTE SEVERE BRAIN AND PITUITARY LESION

1962 ◽  
Vol 40 (2) ◽  
pp. 254-262 ◽  
Author(s):  
H. H. Bassøe ◽  
R. Emberland ◽  
E. Glück ◽  
K. F. Støa
Keyword(s):  
Pituitary Gland ◽  
Adrenal Cortex ◽  
Artificial Ventilation ◽  
Practical Significance ◽  
Adrenocortical Function ◽  
The Third ◽  
Low Levels ◽  
Pituitary Lesion ◽  
Steroid Excretion ◽  
The Brain

ABSTRACT The steroid excretion and the plasma corticosteroids were investigated in three patients with necrosis of the brain and of the pituitary gland. The patients were kept alive by artificial ventilation. In two of the patients the neutral 17-ketosteroids and the 17-hydrocorticosteroids fell to extremely low levels. At the same time, the number of eosinophil cells showed a tendency to increase. Corticotrophin administered intravenously twice to the third patient had a stimulating effect on the adrenal cortex. The theoretical and practical significance of these findings is discussed.

Comparative assessment of informational content of the equations of F.P. Hadlock and the computer program of V.N. Demidov in determination of term of gestation and fetal weight in the III trimester of gestation

2017 ◽  
Author(s):  
E.A. Derkach , O.I. Guseva
Keyword(s):  
Computer Program ◽  
High Precision ◽  
Gestational Age ◽  
Computer Programs ◽  
Comparative Assessment ◽  
Fetal Weight ◽  
Informational Content ◽  
Third Trimester ◽  
The Third

Objectives: to compare the accuracy of equations F.P. Hadlock and computer programs by V.N. Demidov in determining gestational age and fetal weight in the third trimester of gestation. Materials: 328 patients in terms 36–42 weeks of gestation are examined. Ultrasonography was performed in 0–5 days prior to childbirth. Results: it is established that the average mistake in determination of term of pregnancy when using the equation of F.P. Hadlock made 12,5 days, the computer program of V.N. Demidov – 4,4 days (distinction 2,8 times). The mistake within 4 days, when using the equation of F.P. Hadlock has met on average in 23,1 % of observations, the computer program of V.N. Demidov — 65,9 % (difference in 2,9 times). The mistake more than 10 days, took place respectively in 51,7 and 8,2 % (distinction by 6,3 times). At a comparative assessment of size of a mistake in determination of fetal mass it is established that when using the equation of F.P. Hadlock it has averaged 281,0 g, at application of the computer program of V.N. Demidov — 182,5 g (distinction of 54 %). The small mistake in the mass of a fetus which isn't exceeding 200 g at application of the equation of F.P. Hadlock has met in 48,1 % of cases and the computer program of V.N. Demidov — 64,0 % (distinction of 33,1 %). The mistake exceeding 500 g has been stated in 18 % (F.P. Hadlock) and 4,3 % (V.N. Demidov) respectively (distinction 4,2 times). Conclusions: the computer program of V.N. Demidov has high precision in determination of term of a gestation and mass of a fetus in the III pregnancy.

Simultaneous Determination of Imatinib and N-Desmethyl Imatinib in Rat Plasma and Tissues Using LC-MS/MS

2019 ◽  
Vol 15 (2) ◽  
pp. 121-129
Author(s):  
Zhi Rao ◽  
Bo-xia Li ◽  
Yong-Wen Jin ◽  
Wen-Kou ◽  
Yan-rong Ma ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Oral Administration ◽  
Parent Drug ◽  
Gradient Elution ◽  
Biological Tissues ◽  
Rat Plasma ◽  
Running Water ◽  
Liver And Kidney ◽  
The Brain

Background: Imatinib (IM) is a chemotherapy medication metabolized by CYP3A4 to Ndesmethyl imatinib (NDI), which shows similar pharmacologic activity to the parent drug. Although methods for determination of IM and/or NDI have been developed extensively, only few observations have been addressed to simultaneously determine IM and NDI in biological tissues such as liver, kidney, heart, brain and bone marrow. Methods: A validated LC-MS/MS method was developed for the quantitative determination of imatinib (IM) and N-desmethyl imatinib (NDI) from rat plasma, bone marrow, brain, heart, liver and kidney. The plasma samples were prepared by protein precipitation, and then the separation of the analytes was achieved using an Agilent Zorbax Eclipse Plus C18 column (4.6 × 100 mm, 3.5 µm) with gradient elution running water (A) and methanol (B). Mass spectrometric detection was achieved by a triplequadrupole mass spectrometer equipped with an electrospray source interface in positive ionization mode. Results: This method was used to investigate the pharmacokinetics and the tissue distributions in rats following oral administration of 25 mg/kg of IM. The pharmacokinetic profiles suggested that IM and NDI are disappeared faster in rats than human, and the tissue distribution results showed that IM and NDI had good tissue penetration and distribution, except for the brain. This is the first report about the large penetrations of IM and NDI in rat bone marrow. Conclusion: The method demonstrated good sensitivity, accuracy, precision and recovery in assays of IM and NDI in rats. The described assay was successfully applied for the evaluation of pharmacokinetics and distribution in the brain, heart, liver, kidney and bone marrow of IM and NDI after a single oral administration of IM to rats.

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