82 research outputs found
Scientific Discoveries and Technological Inventions: Their Relativistic History Effect
No full textTime … how elusive and slithering, almost feared by the human being, for it disappears through the fingers as when trying to hold water and sand on a beachFil: Arini, Pedro David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática; ArgentinaFil: Bianchi, Jorge.Fil: Valentinuzzi, Max E.
VENTRICULAR FIBRILLATION DETECTION
No full textIn automatic defibrillation, early detection of the arrhythmia constitutes an essential and extremely sensitive task. Its failure means no shock delivery and, hence, no possible reversal leading to the patient’s death. Besides, as Golden Rule, a shock should not be delivered to a collapsed patient not in cardiac arrest and a successfully defibrillated patient should not be defibrillated again. After defining basic evaluating parameters (sensitivity, specificity, receiver operating curve, positive predictivity and accuracy), several algorithms are reviewed comparing them at the end of the chapter in an attempt to help the designer engineer is his/her selection. Acronyms are used along the text for the sake of space knowing the risk of confusion, although frequently their full identification is repeated and realizing that occasionally the same algorithm shares two abbreviations. To make navigation in this chapter easier, find here listed the seven algorithms treated plus other nine mentioned in the discussion, including also two algorithms for QRS complex detection, and calling attention to some overlapping between the two sets, that is: Probability Density Function (PDF), Threshold Crossing Intervals (TCI), Cardiac Frequency (CF), Signal Morphology (SM) or Correlation Waveform Analysis (CWA), Time-Frequency Analysis (TFA), Wavelet Transform (WT), Phase Space Analysis (PSA), in the first group, followed by Threshold Crossing Intervals (TCI), described in section 4.2.2, AutoCorrelation Fischer (ACF95) algorithm, based on Correlation Waveform Analysis (CWA), explained in section 4.2.4, VF Filter algorithm, after Kuo and Dillman (1978); Spectral (SPEC) algorithm based on Fourier Transform analysis, described in section 4.2.5, Complexity (CPLX) algorithm, the Standard Exponential (STE) algorithm, the Modified Exponential Algorithm (MEA), an STE akin, the Signal Comparison Algorithm (SCA), the Wavelet (WVL) Algorithm, also explained in section 4.2.6. Likewise, two QRS complexes detection algorithms are considered: Tompkins (TOMP, see section 4.2.3), and LI algorithm, (see section 4.2.6).Fil: Laciar Leber, Eric. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Valentinuzzi, Maximo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires; Argentina. Universidad Nacional de Tucumán; Argentin
Intracardiac Pressure - Volume Diagrams and Their Links with Thermodynamics
No full textThe main objective of this column is to historically connect the pressure–volume diagram (PVD) of the heat mechanical engines and that of the heart—a natural chemical engine—both types being generators of useful work.Fil: Valentinuzzi, Max E.. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tucumán; ArgentinaFil: Bonomini, Maria Paula. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; ArgentinaFil: Arini, Pedro David. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Ludwig: The Teacher
No full textThis is the third and last article of a series devoted to Carl Friedrich Wilhelm Ludwig's outstanding life (29 December 1816–23 April 1895). The first article portrayed him as a bioengineer [1] and the second as a physiologist [2]. Here, we view him as a teacher, the teacher par excellence, as recognized and commended by Theodor Beer (1866–1919)—a naturalist and physiologist who, incidentally, had a disgraced, sad, and ruined life [3]—making it a dramatic history subject, especially for its several human facets and controversial feelings and beliefs. In his own words: Ludwig war der deutsche Professor par excellence, der deutsche Professor im besten Sinne des Wortes, er war nicht nur tüchtig, sondern auch bedeutend, ein Klassiker in seiner Art.Fil: Valentinuzzi, Max E.. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Beneke, Klaus. Christian-AlbrechtsUniversity; AlemaniaFil: González, Germán Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; Argentin
Laplace's law: Its epistemological context
No full textIn the two preceding notes about Laplace's law, we first recalled what it is and how it is frequently mentioned or applied in physiology, finding that in this particular case, there is an apparent separation between physiology and physics supposedly backing up the subject. Moreover, mistakes are almost a rule while amazingly and fortunately, the overall practical conclusions after very heavy simplifications are correct and well demonstrated by actual experiments and postmortem studies. The second note dealt with the mathematics of the law, and we believe that we practically exhausted all the pathways leading to the final formula, both when the wall thickness is negligible and when it is finite and significant. Now, our hat displays the epistemologist's sign, upsetting perhaps some readers, but without totally leaving out the quantitative view. Hence, the objectives of the note are established as follows: T general objective: To introduce, discuss, and eventually produce answers for the epistemological aspects associated with Laplace's law specific objective: To discern if a mathematical equation has the same reach when obtained from two different physical settings (in our case, a phenomenon found in capillaries and the behavior of hollow stretchable cavities).Fil: Valentinuzzi, Max E.. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; ArgentinaFil: Kohen, Alberto J.. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Zanutto, Bonifacio Silvano. Universidad de Buenos Aires. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Prediction of ventricular fibrillation based on the ST-segment deviation: Allometric model
No full textBased on some reported clinical data, we attempt to apply the allometric law for evaluating the probability of ventricular fibrillation when electrocardiographic ST-segment deviations are determined. The deviation is measured in millimeters at the standard calibration of 1mV = 10mm and the probability in percent. Using the equation VF P = δ + β (ST) in log-log representation, the fitting procedure produced the following overall coefficients: Average β = 1.11, with a maximum = 1.65 and a minimum = 0.78; Average δ = 0.83, with a maximum = 1.39 and a minimum = 0.41. For a 2mm ST-deviation, the full range of predicted ventricular fibrillation probability extended from about 6% at 1 month up to 47% at 4 years after the original cardiac event. These results, at least preliminarily, appear acceptable and still call for full clinical test. The model seems promising if other parameters were taken into account, such as cardiac enzyme concentration, ischemic or infarcted epicardial areas or ejection fraction. It is concluded, considering these results and a few references found in the literature, that the allometric model shows promising features in cardiology.Fil: Arini, Pedro David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; Argentina. Universidad de Buenos Aires. Instituto de Ingeniería Biomédica; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Bonomini, Maria Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; Argentina. Universidad Maimónides; ArgentinaFil: Valentinuzzi, Max E.. Universidad de Buenos Aires. Instituto de Ingeniería Biomédica; Argentina32nd Annual International Conference of the IEEE EMBSArgentinaEl Instituto de Ingenieros Eléctricos y Electrónico
Cardiac Risk Assessment: When and Who?
No full textCardiac fibrillation, both ventricular and atrial, should perhaps be considered as probabilistic phenomena that can be biased according to the pathophysiological condition of the subject. Attempts in this direction have so far been few and vague, and models based on chaos theory, up to now, have been disappointing, even though, at one point in time, the theory sounded appealing, and many papers were produced. In this paper, it has been described the relatively recent historical development of different techniques for cardiac risk assessment, which started with serious quantitative steps in the middle of the 20th century, not more than 50 or 60 years ago, and is part of a much more complex effort aimed at health risk assessment.Fil: Valentinuzzi, Max E.. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; ArgentinaFil: Arini, Pedro David. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Laciar Leber, Eric. Universidad Nacional de San Juan. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bonomini, Maria Paula. Universidad Nacional de San Juan. Facultad de Ingenieria. Departamento de Electronica y Automatica. Gabinete de Tecnologia Medica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Correa, Raul O.. Universidad Nacional de San Juan. Facultad de Ingenieria; Argentin
The brain willis circle and ring electric power systems analogies
No full textBlood flowing to the brain keeps it alive, while electrons flowing to inhabited civilized places keep them active, leading to greater understanding of the world. What, however, of those many human beings still confined to distant hostile regions, unaware of the magic of electricity now over a century old. The word analogy is a synonym of likeness, resemblance, similitude, or affinity and involves two concepts being placed side by side, as in a comparison. The workings of nature and those of human societies are amenable to such analogous comparison?even though the evolution of the natural world obviously spans millions of years, while human societies are much younger, relatively puppies by comparison. This article considers two interesting examples from these two realms that show remarkable similarities (possibly a result of sheer chance), i.e., a circulatory brain anastomosis, the circle of Willis (CW), and modern power transmission-distribution systems in the ring arrangement. Remember that electric networks handle the flow of charges [say, in coulombs per second (C/s) or electric charge per unit time, which is current), whereas hydraulic systems deal with fluid flow [say, in liters per minutes (L/min) or volume/unit time or fluid mass/unit time]. Hence, these systems too are analogous, a well-known fact often mentioned by instructors of electrical engineering courses. Cerebral circulation refers to the movement of blood through the network of blood vessels supplying the brain, the primary governing organ that makes us human beings. The rate of cerebral blood flow in adults is typically 750 mm/min, representing about 15% of cardiac output. The brain is very vulnerable to compromises in its blood supply; consequently, its circulatory system has many safeguards, of which the CW is one. Brain circulatory failure results in cerebrovascular accidents, commonly known as strokes, a health situation of considerable concern.Fil: Valentinuzzi, Maximo. Universidad Nacional de Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Diaz, Ricardo Ruben. Universidad Nacional de Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentin
Neuroendocrinology and its Quantitative Development: A Bioengineering View
No full textAbstract Biomedical engineering is clearly present in modern neuroendocrinology, and indeed has come to embrace it in many respects. First, we briefly review the origins of endocrinology until neuroendocrinology, after a long saga, was established in the 1950's decade with quantified results made possible by the radioimmunoassay technique (RIA), a development contributed by the physical sciences. However, instrumentation was only one face of the quantification process, for mathematical models aiding in the study of negative feedback loops, first rather shyly and now at a growing rate, became means building the edifice of mathematical neuroendocrinology while computer assisted techniques help unravel the associated genetic aspects or the nature itself of endocrine bursts by numerical deconvolution analysis. To end the note, attention is called to the pleiotropic characteristics of neuroendocrinology, which keeps branching off almost endlessly as bioengineering does too.</p
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