A chaotic system with a single unstable node

Energy Technology Data Exchange (ETDEWEB)

Sprott, J.C. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Jafari, Sajad, E-mail: sajadjafari@aut.ac.ir [Biomedical Engineering Department, Amirkabir University of Technology, Tehran 15875-4413 (Iran, Islamic Republic of); Pham, Viet-Thanh [School of Electronics and Telecommunications, Hanoi University of Science and Technology, 01 Dai Co Viet, Hanoi (Viet Nam); Hosseini, Zahra Sadat [Biomedical Engineering Department, Amirkabir University of Technology, Tehran 15875-4413 (Iran, Islamic Republic of)

2015-09-25

This paper describes an unusual example of a three-dimensional dissipative chaotic flow with quadratic nonlinearities in which the only equilibrium is an unstable node. The region of parameter space with bounded solutions is relatively small as is the basin of attraction, which accounts for the difficulty of its discovery. Furthermore, for some values of the parameters, the system has an attracting torus, which is uncommon in three-dimensional systems, and this torus can coexist with a strange attractor or with a limit cycle. The limit cycle and strange attractor exhibit symmetry breaking and attractor merging. All the attractors appear to be hidden in that they cannot be found by starting with initial conditions in the vicinity of the equilibrium, and thus they represent a new type of hidden attractor with important and potentially problematic engineering consequences. - Highlights: • An unusual example of a three-dimensional dissipative chaotic flow is introduced. • In this system the only equilibrium is an unstable node. • For some values of the parameters, the system has an attracting torus. • This torus can coexist with a strange attractor or with a limit cycle. • These properties are uncommon in three-dimensional systems.

Management of hemodynamically unstable pelvic trauma: results of the first Italian consensus conference (cooperative guidelines of the Italian Society of Surgery, the Italian Association of Hospital Surgeons, the Multi-specialist Italian Society of Young Surgeons, the Italian Society of Emergency Surgery and Trauma, the Italian Society of Anesthesia, Analgesia, Resuscitation and Intensive Care, the Italian Society of Orthopaedics and Traumatology, the Italian Society of Emergency Medicine, the Italian Society of Medical Radiology -Section of Vascular and Interventional Radiology- and the World Society of Emergency Surgery)

Science.gov (United States)

2014-01-01

Hemodynamically Unstable Pelvic Trauma is a major problem in blunt traumatic injury. No cosensus has been reached in literature on the optimal treatment of this condition. We present the results of the First Italian Consensus Conference on Pelvic Trauma which took place in Bergamo on April 13 2013. An extensive review of the literature has been undertaken by the Organizing Committee (OC) and forwarded to the Scientific Committee (SC) and the Panel (JP). Members of them were appointed by surgery, critical care, radiology, emergency medicine and orthopedics Italian and International societies: the Italian Society of Surgery, the Italian Association of Hospital Surgeons, the Multi-specialist Italian Society of Young Surgeons, the Italian Society of Emergency Surgery and Trauma, the Italian Society of Anesthesia, Analgesia, Resuscitation and Intensive Care, the Italian Society of Orthopaedics and Traumatology, the Italian Society of Emergency Medicine, the Italian Society of Medical Radiology, Section of Vascular and Interventional Radiology and the World Society of Emergency Surgery. From November 2012 to January 2013 the SC undertook the critical revision and prepared the presentation to the audience and the Panel on the day of the Conference. Then 3 recommendations were presented according to the 3 submitted questions. The Panel voted the recommendations after discussion and amendments with the audience. Later on a email debate took place until December 2013 to reach a unanimous consent. We present results on the 3 following questions: which hemodynamically unstable patient needs an extraperitoneal pelvic packing? Which hemodynamically unstable patient needs an external fixation? Which hemodynamically unstable patient needs emergent angiography? No longer angiography is considered the first therapeutic maneuver in such a patient. Preperitoneal pelvic packing and external fixation, preceded by pelvic binder have a pivotal role in the management of these patients

Systemic and intracardiac hemodynamic disturbance in complicated forms of hepatocirrhosis

International Nuclear Information System (INIS)

Mjasnik, B.N.; Chodzibekov, M.C.; Achmedzanova, S.S.

1990-01-01

On the base of radionuclide investigation of systemic and intracardiac hemodynamics was shown that the rate of kinetic variants of hemocirculation does not depend on the stage of portal hypertension in complicated forms of hepatocirrhosis. Blood redistribution in these patients creates volumentrical overload of cardiac ventricles and pulmonary circulation, that is conditioned of additional tension of cardiac muscle and especially of right ventricle myocardium, which reserve rapidly ran out. Operations which increase blood shunt from portal system to superior vena cava raise preload of myocardium that makes the high risk in appearance of cardiac insufficiency, especially of right ventricle in early post operative period. The received data indicated on necessity to take into account the state of intracardiac hemodynamics in selection of surgical approach in patients with complicated forms of hepatocirrhosis. (orig.) [de

Hemodynamic comparison of mild and severe preeclampsia: concept of stroke systemic vascular resistance index.

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Scardo, J; Kiser, R; Dillon, A; Brost, B; Newman, R

1996-01-01

Our purpose was to compare baseline hemodynamic parameters of mild and severe preeclampsia. Patients admitted to the Medical University Labor and Delivery Unit with the diagnosis of preeclampsia who had not received prior antihypertensive or magnesium sulfate therapy were recruited for noninvasive hemodynamic monitoring with thoracic electrical bioimpedance. After stabilization in the lateral recumbent position, hemodynamic monitoring was begun. Baseline hemodynamic parameters, mean arterial pressure (MAP), heart rate (HR), systemic vascular resistance index (SVRI), cardiac index (CI), and stroke index (SI) were recorded. Stroke systemic vascular resistance index (SSVRI), the resistance imposed by vasculature on each beat of the heart, was calculated for each patient by multiplying SVRI by HR. For statistical analysis, unpaired Student's t-tests (two-tailed) were utilized (P preclampsia appears to be a more intensely vasoconstricted state than mild preeclampsia. Although CI is inversely proportional to SVRI, increased HR in severe preeclampsia prevents this expected decrease in cardiac output.

Porter-Thomas distribution in unstable many-body systems

International Nuclear Information System (INIS)

Volya, Alexander

2011-01-01

We use the continuum shell model approach to explore the resonance width distribution in unstable many-body systems. The single-particle nature of a decay, the few-body character of the interaction Hamiltonian, and the collectivity that emerges in nonstationary systems due to the coupling to the continuum of reaction states are discussed. Correlations between the structures of the parent and daughter nuclear systems in the common Fock space are found to result in deviations of decay width statistics from the Porter-Thomas distribution.

Characterization of the structural collapse undergone by an unstable system of ultrasoft particles

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Prestipino, Santi; Malescio, Gianpietro

2016-09-01

The effective repulsion between macromolecules such as polymer chains or dendrimers is everywhere finite, implying that interaction centers can even coincide. If, in addition, the large-distance attraction is sufficiently strong, then the system is driven unstable. An unstable system lacks a conventional thermodynamics since, in the infinite-size limit, it eventually collapses to a finite-size cluster (for instance, a polymer dispersion undergoes irreversible coagulation when increasing the amount of dissolved salt beyond a certain limit). Using a double-Gaussian (DG) potential for demonstration, we study the phase behavior of a system of ultrasoft particles as a function of the attraction strength η. Above a critical threshold ηc, the DG system is unstable but its collective behavior is far from trivial since two separate regions of the thermodynamic plane can be identified, based on the value taken by the average waiting time for collapse: this is finite and small on one side of the boundary, while presumably infinite in the other region. In order to make sense of this evidence, we consider a stable system of particles interacting through a DG potential augmented with a hard core (stabilized DG, or SDG potential). We provide arguments supporting the view that the boundary line of the unstable DG model is the remnant of the spinodal line of a fluid-fluid phase transition occurring in the SDG model when the hard-core diameter is sent to zero.

Initial and regime situations in the decay of unstable quantum systems

International Nuclear Information System (INIS)

Rimini, A.; Zambotti, G.

1980-01-01

Two different definitions of survival probability in the decay of an unstable quantum system are considered and the equations for them are deduced from the equation for the density operator. The regime situation for the ensemble of unstable systems is studied and the density operator in such a situation is derived. The possible definitions of lifetime are discussed. If the adopted definition makes reference to all time including the early ones, then it is compulsory to specify exactly the state at the initial time. The correct equations for the survival probabilities in such conditions are derived. Two typical examples of decay experiments are considered and the influence of the initial preparation on the mean life is discussed. Numerical examples are given. (author)

Early enteral nutrition in critically ill patients with hemodynamic instability: an evidence-based review and practical advice.

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Yang, Shuofei; Wu, Xingjiang; Yu, Wenkui; Li, Jieshou

2014-02-01

Early enteral nutrition (EEN) in critically ill patients is associated with significant benefit as well as elevated risk of complications. Concomitant use of EEN with vasopressors has been associated with nonocclusive bowel necrosis in critically ill patients with hemodynamic instability. The decision when to initiate enteral nutrition in hemodynamically unstable patients that require vasoactive substances remains a clinical dilemma. This review summarizes the effect of EEN and vasoactive agents on gastrointestinal blood flow and perfusion in critically ill patients, based on current evidence. Animal and clinical data involving simultaneous administration of EEN and vasoactive agents for hemodynamic instability are reviewed, and the factors related to the safety and effectiveness of EEN support in this patient population are analyzed. Moreover, practical recommendations are provided. Additional randomized clinical trials are warranted to provide cutting-edge evidence-based guidance about this issue for practitioners of critical care.

How do classical particle-field systems become unstable? - The last physics problem that Ronald Davidson studied

Science.gov (United States)

Qin, Hong

2016-10-01

Many of the classical particle-field systems in (neutral and nonneutral) plasma physics and accelerator physics become unstable when the system parameters vary. How do these instabilities happen? It turns out, very interestingly, that all conservative systems become unstable by the same mechanism, i.e, the resonance between a positive- and a negative-action modes. And this is the only route that a stable system can become unstable. In this talk, I will use several examples in plasma physics and accelerator physics with finite and infinite degrees of freedom to illustrate the basic physical picture and the rigorous theoretical structure of the process. The features at the transition between stable and unstable regions in the parameter space are the fundamental characteristics of the underlying real Hamiltonian system and complex G-Hamiltonian system. The resonance between a positive- and a negative-action modes at the transition is the Krein collision well-known to mathematicians. Research supported by the U.S. Department of Energy (DE-AC02-09CH11466).

Investigation of unstable periodic space-time states in distributed active system with supercritical current

International Nuclear Information System (INIS)

Koronovskij, A.A.; Rempen, I.S.; Khramov, A.E.

2003-01-01

The set of the unstable periodic space-time states, characterizing the chaotic space-time dynamics of the electron beam with the supercritical current in the Pierce diode is discussed. The Lyapunov indicators of the revealed instable space-time states of the chaotic dynamics of the distributed self-excited system are calculated. It is shown that change in the set of the unstable periodic states in dependence on the Pierce parameter is determined by change in the various orbits stability, which is demonstrated by the values of senior Lyapunov unstable state index [ru

Unstable system with Coulomb interaction distorted near the origin

International Nuclear Information System (INIS)

Kerbikov, B.O.

1981-01-01

An unstable system with Coulomb interaction distorted at small distances is considered. The results are applicable to hadronic atoms analysis. A detailed investigation of the model which can be solved exactly is presented. This model contains the separable short-range potential with the Yamaguchi form factor. Closed expressions for the modified effective range function and the Coulomb-modified scattering length ase obtained [ru

Repeatability of fractional flow reserve despite variations in systemic and coronary hemodynamics

NARCIS (Netherlands)

Johnson, N.P.; Johnson, D.T.; Kirkeeide, R.L.; Berry, C.; de Bruyne, B.; Fearon, W.F.; Oldroyd, K.G.; Pijls, N.H.J.; Gould, K. Lance

2015-01-01

Objectives This study classified and quantified the variation in fractional flow reserve (FFR) due to fluctuations in systemic and coronary hemodynamics during intravenous adenosine infusion. Background Although FFR has become a key invasive tool to guide treatment, questions remain regarding its

Analog Electronic Implementation of Unstable Dissipative Systems of Type I with Multi-Scrolls Displaced Along Space

Science.gov (United States)

Ontañón-García, L. J.; Lozoya-Ponce, R. E.

2017-06-01

Multi-scroll Unstable Dissipative Systems (UDS) in R3 which consist of piecewise linear systems are implemented electronically by means of analog computing. The scrolling behavior of the systems can be designed to oscillate along a specific axis or into space depending on the unstable and stable manifolds. In order for a multi-scroll attractor, this switching system must present at least two unstable hyperbolic focus-saddle equilibria with the same stability index, a negative real eigenvalue and a pair of complex conjugated eigenvalues with positive real part. Then, to displace the scrolls among the axes and space different switching control laws must be designed. By taking into consideration the mathematical expressions of the switching systems, the electronic implementations are carried out by means of operational amplifiers representing the real analog physical solution of the systems, from which the voltage is measured representing the states solution.

Central Hemodynamics and Microcirculation in Critical Conditions

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A. A. Kosovskikh

2013-01-01

Full Text Available Objective: to compare central hemodynamic and microcirculatory changes in critical conditions caused by different factors and to reveal their possible differences for a further differentiated approach to intensive therapy. Subjects and methods. The study covered 16 subjects with severe concomitant injury (mean age 41.96±2.83 years and 19 patients with general purulent peritonitis (mean age 45.34±2.16 years. Their follow-up was 7 days. The central hemodynamics was estimated by transpulmonary thermodilution using a Pulsion PiCCO Plus system (Pulsion Medical Systems, Germany. The microcirculatory bed was evaluated by cutaneous laser Doppler flowmetry using a LAKK-02 capillary blood flow laser analyzer (LAZMA Research-and-Production Association, Russian Federation. Results. The pattern of central hemodynamic and microcirculatory disorders varies with the trigger that has led to a critical condition. Central hemodynamics should be stabilized to ensure the average level of tissue perfusion in victims with severe concomitant injury. In general purulent peritonitis, microcirculatory disorders may persist even if the macrohemodynamic parameters are normal. Conclusion. The macrohemodynamic and microcirculatory differences obtained during the study suggest that a complex of intensive therapy should be differentiated and, if the latter is used, it is necessary not only to be based on the central hemodynamics, but also to take into consideration functional changes in microcirculation. Key words: severe concomitant injury, general purulent peritonitis, micro-circulation, central hemodynamics, type of circulation.

Neonatal Hemodynamics: From Developmental Physiology to Comprehensive Monitoring

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Sabine L. Vrancken

2018-04-01

Full Text Available Maintenance of neonatal circulatory homeostasis is a real challenge, due to the complex physiology during postnatal transition and the inherent immaturity of the cardiovascular system and other relevant organs. It is known that abnormal cardiovascular function during the neonatal period is associated with increased risk of severe morbidity and mortality. Understanding the functional and structural characteristics of the neonatal circulation is, therefore, essential, as therapeutic hemodynamic interventions should be based on the assumed underlying (pathophysiology. The clinical assessment of systemic blood flow (SBF by indirect parameters, such as blood pressure, capillary refill time, heart rate, urine output, and central-peripheral temperature difference is inaccurate. As blood pressure is no surrogate for SBF, information on cardiac output and systemic vascular resistance should be obtained in combination with an evaluation of end organ perfusion. Accurate and reliable hemodynamic monitoring systems are required to detect inadequate tissue perfusion and oxygenation at an early stage before this result in irreversible damage. Also, the hemodynamic response to the initiated treatment should be re-evaluated regularly as changes in cardiovascular function can occur quickly. New insights in the understanding of neonatal cardiovascular physiology are reviewed and several methods for current and future neonatal hemodynamic monitoring are discussed.

Unstable patients with retroperitoneal vascular trauma: an endovascular approach.

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Boufi, Mourad; Bordon, Sébastien; Dona, Bianca; Hartung, Olivier; Sarran, Anthony; Nadeau, Sébastien; Maurin, Charlotte; Alimi, Yves S

2011-04-01

In hemodynamically unstable patients, the management of retroperitoneal vascular trauma is both difficult and challenging. Endovascular techniques have become an alternative to surgery in several trauma centers. Between 2004 and 2006, 16 patients (nine men, mean age: 46 years, range: 19-79 years) with retroperitoneal vascular trauma and hemodynamic instability were treated using an endovascular approach. The mean injury severity score was 30.7 ± 13.1. Mean systolic blood pressure and the shock index were 74 mm Hg and 1.9, respectively. Vasopressor drugs were required in 68.7% of cases (n = 11). Injuries were attributable to road traffic accidents (n = 15) and falls (n = 1). The hemorrhage sites included the internal iliac artery or its branches (n = 12) with bilateral injury in one case, renal artery (n = 2), abdominal aorta (n = 1), and lumbar artery (n = 1). In all, 14 coil embolizations and three stent-grafts were implanted. The technical success rate was 75%, as early re-embolization was necessary in one case and three patients died during the perioperative period. Six patients died during the period of hospitalization (37.5%). No surgical conversion or major morbidity was reported. In comparison with particulates, coil ± stent-graft may provide similar efficacy with regard to survival, and thus may be a valuable solution when particulate embolization is not available or feasible. Copyright © 2011 Annals of Vascular Surgery Inc. Published by Elsevier Inc. All rights reserved.

Modeling and control of an unstable system using probabilistic fuzzy inference system

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Sozhamadevi N.

2015-09-01

Full Text Available A new type Fuzzy Inference System is proposed, a Probabilistic Fuzzy Inference system which model and minimizes the effects of statistical uncertainties. The blend of two different concepts, degree of truth and probability of truth in a unique framework leads to this new concept. This combination is carried out both in Fuzzy sets and Fuzzy rules, which gives rise to Probabilistic Fuzzy Sets and Probabilistic Fuzzy Rules. Introducing these probabilistic elements, a distinctive probabilistic fuzzy inference system is developed and this involves fuzzification, inference and output processing. This integrated approach accounts for all of the uncertainty like rule uncertainties and measurement uncertainties present in the systems and has led to the design which performs optimally after training. In this paper a Probabilistic Fuzzy Inference System is applied for modeling and control of a highly nonlinear, unstable system and also proved its effectiveness.

Effect of volume expansion on systemic hemodynamics and central and arterial blood volume in cirrhosis

DEFF Research Database (Denmark)

Møller, S; Bendtsen, F; Henriksen, Jens Henrik Sahl

1995-01-01

, and arterial pressure were determined before and during a volume expansion induced by infusion of a hyperosmotic galactose solution. RESULTS: During volume expansion, the central and arterial blood volume increased significantly in patients with class A and controls, whereas no significant change was found...... in patients with either class B or class C. Conversely, the noncentral blood volume increased in patients with class B and C. In both patients and controls, the cardiac output increased and the systemic vascular resistance decreased, whereas the mean arterial blood pressure did not change significantly......BACKGROUND & AIMS: Systemic vasodilatation in cirrhosis may lead to hemodynamic alterations with reduced effective blood volume and decreased arterial blood pressure. This study investigates the response of acute volume expansion on hemodynamics and regional blood volumes in patients with cirrhosis...

Intraoperative non-record-keeping usage of anesthesia information management system workstations and associated hemodynamic variability and aberrancies.

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Wax, David B; Lin, Hung-Mo; Reich, David L

2012-12-01

Anesthesia information management system workstations in the anesthesia workspace that allow usage of non-record-keeping applications could lead to distraction from patient care. We evaluated whether non-record-keeping usage of the computer workstation was associated with hemodynamic variability and aberrancies. Auditing data were collected on eight anesthesia information management system workstations and linked to their corresponding electronic anesthesia records to identify which application was active at any given time during the case. For each case, the periods spent using the anesthesia information management system record-keeping module were separated from those spent using non-record-keeping applications. The variability of heart rate and blood pressure were also calculated, as were the incidence of hypotension, hypertension, and tachycardia. Analysis was performed to identify whether non-record-keeping activity was a significant predictor of these hemodynamic outcomes. Data were analyzed for 1,061 cases performed by 171 clinicians. Median (interquartile range) non-record-keeping activity time was 14 (1, 38) min, representing 16 (3, 33)% of a median 80 (39, 143) min of procedure time. Variables associated with greater non-record-keeping activity included attending anesthesiologists working unassisted, longer case duration, lower American Society of Anesthesiologists status, and general anesthesia. Overall, there was no independent association between non-record-keeping workstation use and hemodynamic variability or aberrancies during anesthesia either between cases or within cases. Anesthesia providers spent sizable portions of case time performing non-record-keeping applications on anesthesia information management system workstations. This use, however, was not independently associated with greater hemodynamic variability or aberrancies in patients during maintenance of general anesthesia for predominantly general surgical and gynecologic procedures.

Hemodynamic analysis of sequential graft from right coronary system to left coronary system.

Science.gov (United States)

Wang, Wenxin; Mao, Boyan; Wang, Haoran; Geng, Xueying; Zhao, Xi; Zhang, Huixia; Xie, Jinsheng; Zhao, Zhou; Lian, Bo; Liu, Youjun

2016-12-28

Sequential and single grafting are two surgical procedures of coronary artery bypass grafting. However, it remains unclear if the sequential graft can be used between the right and left coronary artery system. The purpose of this paper is to clarify the possibility of right coronary artery system anastomosis to left coronary system. A patient-specific 3D model was first reconstructed based on coronary computed tomography angiography (CCTA) images. Two different grafts, the normal multi-graft (Model 1) and the novel multi-graft (Model 2), were then implemented on this patient-specific model using virtual surgery techniques. In Model 1, the single graft was anastomosed to right coronary artery (RCA) and the sequential graft was adopted to anastomose left anterior descending (LAD) and left circumflex artery (LCX). While in Model 2, the single graft was anastomosed to LAD and the sequential graft was adopted to anastomose RCA and LCX. A zero-dimensional/three-dimensional (0D/3D) coupling method was used to realize the multi-scale simulation of both the pre-operative and two post-operative models. Flow rates in the coronary artery and grafts were obtained. The hemodynamic parameters were also showed, including wall shear stress (WSS) and oscillatory shear index (OSI). The area of low WSS and OSI in Model 1 was much less than that in Model 2. Model 1 shows optimistic hemodynamic modifications which may enhance the long-term patency of grafts. The anterior segments of sequential graft have better long-term patency than the posterior segments. With rational spatial position of the heart vessels, the last anastomosis of sequential graft should be connected to the main branch.

The Fate of Unstable Circumbinary Planets

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Kohler, Susanna

2016-03-01

What happens to Tattooine-like planets that are instead in unstable orbits around their binary star system? A new study examines whether such planets will crash into a host star, get ejected from the system, or become captured into orbit around one of their hosts.Orbit Around a DuoAt this point we have unambiguously detected multiple circumbinary planets, raising questions about these planets formation and evolution. Current models suggest that it is unlikely that circumbinary planets would be able to form in the perturbed environment close their host stars. Instead, its thought that the planets formed at a distance and then migrated inwards.One danger such planets face when migrating is encountering ranges of radii where their orbits become unstable. Two scientists at the University of Chicago, Adam Sutherland and Daniel Fabrycky, have studied what happens when circumbinary planets migrate into such a region and develop unstable orbits.Producing Rogue PlanetsTime for planets to either be ejected or collide with one of the two stars, as a function of the planets starting distance (in AU) from the binary barycenter. Colors represent different planetary eccentricities. [Sutherland Fabrycky 2016]Sutherland and Fabrycky used N-body simulations to determine the fates of planets orbiting around a star system consisting of two stars a primary like our Sun and a secondary roughly a tenth of its size that are separated by 1 AU.The authors find that the most common fate for a circumbinary planet with an unstable orbit is ejection from the system; over 80% of unstable planets were ejected. This has interesting implications: if the formation of circumbinary planets is common, this mechanism could be filling the Milky Way with a population of free-floating, rogue planets that no longer are associated with their host star.The next most common outcome for unstable planets is collision with one of their host stars (most often the secondary), resulting inaccretion of the planet

Unstable Systems in Relativistic Quantum Field Theory

CERN Document Server

Maiani, Luciano

1998-01-01

We show how the state of an unstable particle can be defined in terms of stable asymptotic states. This general definition is used to discuss and to solve some old problems connected with the short-time and large-time behaviour of the non-decay amplitude.

Cold or hot, stable or unstable collective nuclear motion

International Nuclear Information System (INIS)

Chomaz, Ph.; Lacroix, D.; Jacquot, B.; Colonna, M.; Ayik, S.

1999-01-01

We present a general discussion of the mean field dynamics of finite nuclei prepared under extreme of temperature and pressure. Many features of the dynamics are carefully studied such as the collective expansion, the evaporation process, the different time-scale. We show that under the thermal pressure and the effect of the compression, the system may reach low density regions where it may become unstable. Early development of the instabilities in a dilute nuclear source in investigated using a finite temperature quantal Rpa approach for different systems. The growth rates of the unstable collective modes are determining by solving a dispersion relation. Which is obtained by parameterizing the transition density in terms of its multipole moments. Under typical conditions of a dilute finite system at moderate temperatures the dispersion relation exhibits an ultraviolet cut-off. As a result, only a finite number of multiple modes becomes unstable , and the number of the unstable collective modes increases with the size of the source. Calculations indicate that for an expanding source, unstable modes show a transition from surface to volume character. (author)

Effects of Dietary Nitrates on Systemic and Cerebrovascular Hemodynamics

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Vernon Bond

2013-01-01

Full Text Available Cerebral blood flow dysregulation is often associated with hypertension. We hypothesized that a beetroot juice (BRJ treatment could decrease blood pressure and cerebrovascular resistance (CVR. We subjected 12 healthy females to control and BRJ treatments. Cerebrovascular resistance index (CVRI, systolic blood pressure (SBP, total vascular resistance (TVR, and the heart rate-systolic pressure product (RPP measured at rest and at two exercise workloads were lower after the BRJ treatment. CVRI, SBP, and RPP were lower without a lower TVR at the highest exercise level. These findings suggest improved systemic and cerebral hemodynamics that could translate into a dietary treatment for hypertension.

Occupational exposure in hemodynamic

International Nuclear Information System (INIS)

Silva, Amanda J.; Fernandes, Ivani M.; Silva, Paula P. Nou; Sordi, Gian Maria A.A.; Carneiro, Janete C.G.G.

2011-01-01

This paper has an objective to perform a radiometric survey at a hemodynamic service. Besides, it was intended to evaluate the effective dose of health professionals and to provide data which can contribute with minimization of exposures during the realization of hemodynamic procedure. The radiometric survey was realized in the real environment of work simulating the conditions of a hemodynamic study with a ionization chamber

The nursing perspective on monitoring hemodynamics and oxygen transport.

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Tucker, Dawn; Hazinski, Mary Fran

2011-07-01

Maintenance of adequate systemic oxygen delivery requires careful clinical assessment integrated with hemodynamic measurements and calculations to detect and treat conditions that may compromise oxygen delivery and lead to life-threatening shock, respiratory failure, or cardiac arrest. The bedside nurse constantly performs such assessments and measurements to detect subtle changes and trends in patient condition. The purpose of this editorial is to highlight nursing perspectives about the hemodynamic and oxygen transport monitoring systems summarized in the Pediatric Cardiac Intensive Care Society Evidence- Based Review and Consensus Statement on Monitoring of Hemodynamics and Oxygen Transport Balance. There is no substitute for the observations of a knowledgeable and experienced clinician who understands the patient's condition and potential causes of deterioration and is able to evaluate response to therapy.

The influence of systemic hemodynamics and oxygen transport on cerebral oxygen saturation in neonates after the Norwood procedure.

Science.gov (United States)

Li, Jia; Zhang, Gencheng; Holtby, Helen; Guerguerian, Anne-Marie; Cai, Sally; Humpl, Tilman; Caldarone, Christopher A; Redington, Andrew N; Van Arsdell, Glen S

2008-01-01

Ischemic brain injury is an important morbidity in neonates after the Norwood procedure. Its relationship to systemic hemodynamic oxygen transport is poorly understood. Sixteen neonates undergoing the Norwood procedure were studied. Continuous cerebral oxygen saturation was measured by near-infrared spectroscopy. Continuous oxygen consumption was measured by respiratory mass spectrometry. Pulmonary and systemic blood flow, systemic vascular resistance, oxygen delivery, and oxygen extraction ratio were derived with measurements of arterial, and superior vena cava and pulmonary venous gases and pressures at 2- to 4-hour intervals during the first 72 hours in the intensive care unit. Mean cerebral oxygen saturation was 66% +/- 12% before the operation, reduced to 51% +/- 13% on arrival in the intensive care unit, and remained low during the first 8 hours; it increased to 56% +/- 9% at 72 hours, still significantly lower than the preoperative level (P blood flow and oxygen delivery (P blood flow (P = .001) and hemoglobin (P = .02) and negatively correlated with systemic vascular resistance (P = .003). It was not correlated with oxygen consumption (P > .05). Cerebral oxygen saturation decreased significantly in neonates during the early postoperative period after the Norwood procedure and was significantly influenced by systemic hemodynamic and metabolic events. As such, hemodynamic interventions to modify systemic oxygen transport may provide further opportunities to reduce the risk of cerebral ischemia and improve neurodevelopmental outcomes.

CMOS Image Sensor and System for Imaging Hemodynamic Changes in Response to Deep Brain Stimulation.

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Zhang, Xiao; Noor, Muhammad S; McCracken, Clinton B; Kiss, Zelma H T; Yadid-Pecht, Orly; Murari, Kartikeya

2016-06-01

Deep brain stimulation (DBS) is a therapeutic intervention used for a variety of neurological and psychiatric disorders, but its mechanism of action is not well understood. It is known that DBS modulates neural activity which changes metabolic demands and thus the cerebral circulation state. However, it is unclear whether there are correlations between electrophysiological, hemodynamic and behavioral changes and whether they have any implications for clinical benefits. In order to investigate these questions, we present a miniaturized system for spectroscopic imaging of brain hemodynamics. The system consists of a 144 ×144, [Formula: see text] pixel pitch, high-sensitivity, analog-output CMOS imager fabricated in a standard 0.35 μm CMOS process, along with a miniaturized imaging system comprising illumination, focusing, analog-to-digital conversion and μSD card based data storage. This enables stand alone operation without a computer, nor electrical or fiberoptic tethers. To achieve high sensitivity, the pixel uses a capacitive transimpedance amplifier (CTIA). The nMOS transistors are in the pixel while pMOS transistors are column-parallel, resulting in a fill factor (FF) of 26%. Running at 60 fps and exposed to 470 nm light, the CMOS imager has a minimum detectable intensity of 2.3 nW/cm(2) , a maximum signal-to-noise ratio (SNR) of 49 dB at 2.45 μW/cm(2) leading to a dynamic range (DR) of 61 dB while consuming 167 μA from a 3.3 V supply. In anesthetized rats, the system was able to detect temporal, spatial and spectral hemodynamic changes in response to DBS.

Management of hemodynamically unstable pelvic fracture in pregnancy: a case report and review of literature

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ZHANG Peng

2012-08-01

Full Text Available 【Abstract】 We present an unusual case of an un-stable pelvic fracture during pregnancy period, who suf-fered fetal death and splenic rupture simultaneously which developed massive delayed hemorrhage in abdomen. When considering potential causes of fetal death, direct trauma to the uterus, placenta, or fetus was not associated with a higher fetal mortality rate, compared with maternal hemorrhage. A cesarean section and splenectomy could res-cue the maternal life from the hemorrhage situation. Suc-cessful treatment of these rare cases is possible with careful pre-, peri-, and post-operative evaluation of the mother and fetus by a multidisciplinary team. Key words: Pelvis fracture; Pregnancy; Splenic rupture; Fetal death

High-resolution simulations of unstable cylindrical gravity currents undergoing wandering and splitting motions in a rotating system

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Dai, Albert; Wu, Ching-Sen

2018-02-01

High-resolution simulations of unstable cylindrical gravity currents when wandering and splitting motions occur in a rotating system are reported. In this study, our attention is focused on the situation of unstable rotating cylindrical gravity currents when the ratio of Coriolis to inertia forces is larger, namely, 0.5 ≤ C ≤ 2.0, in comparison to the stable ones when C ≤ 0.3 as investigated previously by the authors. The simulations reproduce the major features of the unstable rotating cylindrical gravity currents observed in the laboratory, i.e., vortex-wandering or vortex-splitting following the contraction-relaxation motion, and good agreement is found when compared with the experimental results on the outrush radius of the advancing front and on the number of bulges. Furthermore, the simulations provide energy budget information which could not be attained in the laboratory. After the heavy fluid is released, the heavy fluid collapses and a contraction-relaxation motion is at work for approximately 2-3 revolutions of the system. During the contraction-relaxation motion of the heavy fluid, the unstable rotating cylindrical gravity currents behave similar to the stable ones. Towards the end of the contraction-relaxation motion, the dissipation rate in the system reaches a local minimum and a quasi-geostrophic equilibrium state is reached. After the quasi-geostrophic equilibrium state, vortex-wandering or vortex-splitting may occur depending on the ratio of Coriolis to inertia forces. The vortex-splitting process begins with non-axisymmetric bulges and, as the bulges grow, the kinetic energy increases at the expense of decreasing potential energy in the system. The completion of vortex-splitting is accompanied by a local maximum of dissipation rate and a local maximum of kinetic energy in the system. A striking feature of the unstable rotating cylindrical gravity currents is the persistent upwelling and downwelling motions, which are observed for both the

Numerical detection of unstable periodic orbits in continuous-time dynamical systems with chaotic behaviors

Directory of Open Access Journals (Sweden)

Y. Saiki

2007-09-01

Full Text Available An infinite number of unstable periodic orbits (UPOs are embedded in a chaotic system which models some complex phenomenon. Several algorithms which extract UPOs numerically from continuous-time chaotic systems have been proposed. In this article the damped Newton-Raphson-Mees algorithm is reviewed, and some important techniques and remarks concerning the practical numerical computations are exemplified by employing the Lorenz system.

Systemic and regional hemodynamic effects of enalaprilat infusion in experimental normotensive sepsis

Directory of Open Access Journals (Sweden)

L. Rahal

Full Text Available Angiotensin-converting enzyme inhibitors have been shown to improve splanchnic perfusion in distinct shock states. We hypothesized that enalaprilat potentiates the benefits of early fluid resuscitation in severe experimental sepsis, particularly in the splanchnic region. Anesthetized and mechanically ventilated mongrel dogs received an intravenous infusion of live Escherichia coli over a period of 30 min. Thereafter, two interventions were performed: fluid infusion (normal saline, 32 mL/kg over 30 min and enalaprilat infusion (0.02 mg kg-1 min-1 for 60 min in randomized groups. The following groups were studied: controls (fluid infusion, N = 4, E1 (enalaprilat infusion followed by fluid infusion, N = 5 and E2 (fluid infusion followed by enalaprilat infusion, N = 5. All animals were observed for a 120 min after bacterial infusion. Mean arterial pressure, cardiac output (CO, portal vein blood flow (PVBF, systemic and regional oxygen-derived variables, and lactate levels were measured. Rapid and progressive reductions in CO and PVBF were induced by the infusion of live bacteria, while minor changes were observed in mean arterial pressure. Systemic and regional territories showed a significant increase in oxygen extraction and lactate levels. Widening venous-arterial and portal-arterial pCO2 gradients were also detected. Fluid replacement promoted transient benefits in CO and PVBF. Enalaprilat after fluid resuscitation did not affect systemic or regional hemodynamic variables. We conclude that in this model of normotensive sepsis inhibition of angiotensin-converting enzyme did not interfere with the course of systemic or regional hemodynamic and oxygen-derived variables.

Quantifying the abnormal hemodynamics of sickle cell anemia

Science.gov (United States)

Lei, Huan; Karniadakis, George

2012-02-01

Sickle red blood cells (SS-RBC) exhibit heterogeneous morphologies and abnormal hemodynamics in deoxygenated states. A multi-scale model for SS-RBC is developed based on the Dissipative Particle Dynamics (DPD) method. Different cell morphologies (sickle, granular, elongated shapes) typically observed in deoxygenated states are constructed and quantified by the Asphericity and Elliptical shape factors. The hemodynamics of SS-RBC suspensions is studied in both shear and pipe flow systems. The flow resistance obtained from both systems exhibits a larger value than the healthy blood flow due to the abnormal cell properties. Moreover, SS-RBCs exhibit abnormal adhesive interactions with both the vessel endothelium cells and the leukocytes. The effect of the abnormal adhesive interactions on the hemodynamics of sickle blood is investigated using the current model. It is found that both the SS-RBC - endothelium and the SS-RBC - leukocytes interactions, can potentially trigger the vicious ``sickling and entrapment'' cycles, resulting in vaso-occlusion phenomena widely observed in micro-circulation experiments.

[System analytical approach of lung function and hemodynamics].

Science.gov (United States)

Naszlady, Attila; Kiss, Lajos

2009-02-15

The authors critically analyse the traditional views in physiology and complete them with new statements based on computer model simulations of lung function and of hemodynamics. Conclusions are derived for the clinical practice as follows: the four-dimensional function curves are similar in both systems; there is a "waterfall" zone in the pulmonary blood perfusion; the various time constants of pulmonary regions can modify the blood gas values; pulmonary capillary pressure is equal to pulmonary arterial diastole pressure; heart is not a pressure pump, but a flow source; ventricles are loaded by the input impedance of the arterial systems and not by the total vascular (ohmlike) resistance; optimum heart rate in rest depends on the length of the aorta; this law of heart rate, based on the principle of resonance is valid along the mammalian allometric line; tachycardia decreases the input impedance; using positive end expiratory pressure respirators the blood gas of pulmonary artery should be followed; coronary circulation should be assessed in beat per milliliter, the milliliter per minute may be false. These statements are compared to related references.

Prospective evaluation of intraoperative hemodynamics in liver transplantation with whole, partial and DCD grafts

NARCIS (Netherlands)

Sainz-Barriga, M; Reyntjens, K; Costa, M G; Scudeller, L; Rogiers, X; Wouters, P; de Hemptinne, B; Troisi, R I

The interaction of systemic hemodynamics with hepatic flows at the time of liver transplantation (LT) has not been studied in a prospective uniform way for different types of grafts. We prospectively evaluated intraoperative hemodynamics of 103 whole and partial LT. Liver graft hemodynamics were

Predictive value of focused assessment with sonography for trauma (FAST) for laparotomy in unstable polytrauma Egyptians patients.

Science.gov (United States)

Elbaih, Adel Hamed; Abu-Elela, Sameh T

2017-12-01

The emergency physicians face significant clinical uncertainty when multiple trauma patients arrive in the emergency department (ED). The priorities for assessment and treatment of polytrauma patients are established in the primary survey. Focused assessment with sonography for trauma (FAST) is very essential clinical skill during trauma resuscitation. Use of point of care ultrasound among the trauma team working in the primary survey in emergency care settings is lacking in Suez Canal University Hospitals even ultrasound machine not available in ED. This study aims to evaluate the accuracy of FAST in hemodynamically unstable polytraumatized patients and to determine its role as an indication of laparotomy. This study is a cross-sectional study included 150 polytrauma patients with a blunt mechanism admitted in Suez Canal University Hospital. Firstly primary survey by airway check, cervical spine securing with neck collar, maintenance of breathing/circulation and management of life threading conditions if present were conducted accordingly to ATLS (advanced trauma life support) guidelines. The patients were assessed in the primary survey using the FAST as a tool to determine the presence of intra-abdominal collection. A total of 150 patients, and FAST scans were performed in all cases. The sensitivity and specificity were 92.6% and 100%, respectively. The negative predictive value was 92%, while the positive predictive value of FAST was 100%. The accuracy of FAST was 96%. FAST is an important method to detect intra-abdominal fluid in the initial assessment in hemodynamically unstable polytrauma patients with high accuracy. Copyright © 2017 Daping Hospital and the Research Institute of Surgery of the Third Military Medical University. Production and hosting by Elsevier B.V. All rights reserved.

Hemodynamic changes after levothyroxine treatment in subclinical hypothyroidism

DEFF Research Database (Denmark)

Faber, J; Petersen, L; Wiinberg, N

2002-01-01

by LT(4) (p treatment in SH results in changes in hemodynamic parameters of potentially beneficial character. SH and overt hypothyroidism should......In hypothyroidism, lack of thyroid hormones results in reduced cardiac function (cardiac output [CO]), and an increase of systemic vascular resistance (SVR). We speculated whether hemodynamic regulation in subjects with subclinical hypothyroidism (SH) (defined as mildly elevated thyrotropin [TSH......) and T(3) estimates) LT(4) treatment resulted in 6% reduction in supine MAP (p treatment (p

Avoiding unstable regions in the design space of EUV mirror systems comprising high-order aspheric surfaces

NARCIS (Netherlands)

Marinescu, O.; Bociort, F.; Braat, J.

2004-01-01

When Extreme Ultraviolet mirror systems having several high-order aspheric surfaces are optimized, the configurations often enter into highly unstable regions of the parameter space. Small changes of system parameters lead then to large changes in ray paths, and therefore optimization algorithms

Revealing Bell's nonlocality for unstable systems in high energy physics

International Nuclear Information System (INIS)

Hiesmayr, Beatrix C.; Gabriel, Andreas; Huber, Marcus; Di Domenico, Antonio; Curceanu, Catalina; Larsson, Jan-Aake; Moskal, Pawel

2012-01-01

Entanglement and its consequences - in particular the violation of Bell inequalities, which defies our concepts of realism and locality - have been proven to play key roles in Nature by many experiments for various quantum systems. Entanglement can also be found in systems not consisting of ordinary matter and light, i.e. in massive meson-antimeson systems. Bell inequalities have been discussed for these systems, but up to date no direct experimental test to conclusively exclude local realism was found. This mainly stems from the fact that one only has access to a restricted class of observables and that these systems are also decaying. In this Letter we put forward a Bell inequality for unstable systems which can be tested at accelerator facilities with current technology. Herewith, the long awaited proof that such systems at different energy scales can reveal the sophisticated ''dynamical'' nonlocal feature of Nature in a direct experiment gets feasible. Moreover, the role of entanglement and CP violation, an asymmetry between matter and antimatter, is explored, a special feature offered only by these meson-antimeson systems. (orig.)

Ongoing right ventricular hemodynamics in heart failure: clinical value of measurements derived from an implantable monitoring system.

Science.gov (United States)

Adamson, Philip B; Magalski, Anthony; Braunschweig, Frieder; Böhm, Michael; Reynolds, Dwight; Steinhaus, David; Luby, Allyson; Linde, Cecilia; Ryden, Lars; Cremers, Bodo; Takle, Teri; Bennett, Tom

2003-02-19

This study examined the characteristics of continuously measured right ventricular (RV) hemodynamic information derived from an implantable hemodynamic monitor (IHM) in heart failure patients. Hemodynamic monitoring might improve the day-to-day management of patients with chronic heart failure (CHF). Little is known about the characteristics of long-term hemodynamic information in patients with CHF or how such information relates to meaningful clinical events. Thirty-two patients with CHF received a permanent RV IHM system similar to a single-lead pacemaker. Right ventricular systolic and diastolic pressures, heart rate, and pressure derivatives were continuously measured for nine months without using the data for clinical decision-making or management of patients. Data were then made available to clinical providers, and the patients were followed up for 17 months. Pressure characteristics during optimal volume, clinically determined volume-overload exacerbations, and volume depletion events were examined. The effect of IHM on hospitalizations was examined using the patients' historical controls. Long-term RV pressure measurements had either marked variability or minimal time-related changes. During 36 volume-overload events, RV systolic pressures increased by 25 +/- 4% (p < 0.05) and heart rate increased by 11 +/- 2% (p < 0.05). Pressure increases occurred in 9 of 12 events 4 +/- 2 days before the exacerbations requiring hospitalization. Hospitalizations before using IHM data for clinical management averaged 1.08 per patient year and decreased to 0.47 per patient-year (57% reduction, p < 0.01) after hemodynamic data were used. Long-term ambulatory pressure measurements from an IHM may be helpful in guiding day-to-day clinical management, with a potentially favorable impact on CHF hospitalizations.

Hemodynamic, morphometric and autonomic patterns in hypertensive rats - renin-angiotensin system modulation

Directory of Open Access Journals (Sweden)

Fernanda S. Zamo

2010-01-01

Full Text Available BACKGROUND: Spontaneously hypertensive rats develop left ventricular hypertrophy, increased blood pressure and blood pressure variability, which are important determinants of heart damage, like the activation of renin-angiotensin system. AIMS: To investigate the effects of the time-course of hypertension over 1 hemodynamic and autonomic patterns (blood pressure; blood pressure variability; heart rate; 2 left ventricular hypertrophy; and 3 local and systemic Renin-angiotensin system of the spontaneously hypertensive rats. METHODS: Male spontaneously hypertensive rats were randomized into two groups: young (n=13 and adult (n=12. Hemodynamic signals (blood pressure, heart rate, blood pressure variability (BPV and spectral analysis of the autonomic components of blood pressure were analyzed. LEFT ventricular hypertrophy was measured by the ratio of LV mass to body weight (mg/g, by myocyte diameter (μm and by relative fibrosis area (RFA, %. ACE and ACE2 activities were measured by fluorometry (UF/min, and plasma renin activity (PRA was assessed by a radioimmunoassay (ng/mL/h. Cardiac gene expressions of Agt, Ace and Ace2 were quantified by RT-PCR (AU. RESULTS: The time-course of hypertension in spontaneously hypertensive rats increased BPV and reduced the alpha index in adult spontaneously hypertensive rats. Adult rats showed increases in left ventricular hypertrophy and in RFA. Compared to young spontaneously hypertensive rats, adult spontaneously hypertensive rats had lower cardiac ACE and ACE2 activities, and high levels of PRA. No change was observed in gene expression of Renin-angiotensin system components. CONCLUSIONS: The observed autonomic dysfunction and modulation of Renin-angiotensin system activity are contributing factors to end-organ damage in hypertension and could be interacting. Our findings suggest that the management of hypertensive disease must start before blood pressure reaches the highest stable levels and the consequent

[Treatment aspects of unstable angina. Costs and payments for DRG].

Science.gov (United States)

Brunelli, C; Spallarossa, P; Pasdera, A; Bezante, G P; Zorzet, F; Rossettin, P

1998-01-01

Patients with unstable angina fall into a wide prognostic and therapeutic spectrum but, in general, have great access to specialty care and invasive procedures. In the modern era, in which admissions for unstable angina outnumber those for myocardial infarction, and growing economic pressures are placed on health care systems, cardiologists must re-examine clinical strategies for treating unstable angina in the light of health-cost accounting. The aims of the present study were to examine the current management of patients admitted to our cardiology department and to calculate the medical costs. A patient schedule was drawn up to prospectively register the number and type of cardiac processes carried out during hospitalization for all unstable angina patients in the period between March 1st and May 30th, 1995. Time (minutes) actually spent by both physicians and nurses for each cardiac process were carefully recorded in order to calculate the activity budget. The effective economic budget was built for each cardiac process taking into account salaries, consumable supplies, equipment service contracts, depreciation and indirect medical and non medical costs for CCU and ward. Based to the Diagnosis Related Groups (DRG) system, 53 out of 318 patients (16%) were admitted with documented or suspected unstable angina and allocated to discharge into four DRGs: DRG 140-medically treated unstable angina: 18 patients; DRG 124-unstable angina with angiography: 16 patients; DRG 122-unstable angina evolving in myocardial infarction: 6 patients; DRG 112-unstable angina with angioplasty: 13 patients. The mean cost for hospitalized patient with unstable angina was 5,574,958 Italian Liras (DRG 140 = 2,687,719; DRG 124 = 2,800,347; DRG 122 = 6,086,563; DRG 112 = 12,751,454). The difference in costs was essentially related to the procedures involved in medical care, DRGs with expensive cardiac processes having higher costs. Furthermore, these data show a deep discrepancy between

Symptom-Hemodynamic Mismatch and Heart Failure Event Risk

Science.gov (United States)

Lee, Christopher S.; Hiatt, Shirin O.; Denfeld, Quin E.; Mudd, James O.; Chien, Christopher; Gelow, Jill M.

2014-01-01

Background Heart failure (HF) is a heterogeneous condition of both symptoms and hemodynamics. Objective The goal of this study was to identify distinct profiles among integrated data on physical and psychological symptoms and hemodynamics, and quantify differences in 180-day event-risk among observed profiles. Methods A secondary analysis of data collected during two prospective cohort studies by a single group of investigators was performed. Latent class mixture modeling was used to identify distinct symptom-hemodynamic profiles. Cox proportional hazards modeling was used to quantify difference in event-risk (HF emergency visit, hospitalization or death) among profiles. Results The mean age (n=291) was 57±13 years, 38% were female, and 61% had class III/IV HF. Three distinct symptom-hemodynamic profiles were identified. 17.9% of patients had concordant symptoms and hemodynamics (i.e. moderate physical and psychological symptoms matched the comparatively hemodynamic profile), 17.9% had severe symptoms and average hemodynamics, and 64.2% had poor hemodynamics and mild symptoms. Compared to those in the concordant profile, both profiles of symptom-hemodynamic mismatch were associated with a markedly increased event-risk (severe symptoms hazards ratio = 3.38, p=0.033; poor hemodynamics hazards ratio = 3.48, p=0.016). Conclusions A minority of adults with HF have concordant symptoms and hemodynamics. Either profile of symptom-hemodynamic mismatch in HF is associated with a greater risk of healthcare utilization for HF or death. PMID:24988323

Hemodynamic monitoring in the critically ill.

Science.gov (United States)

Voga, G

1995-06-01

Monitoring of vital functions is one of the most important and essential tools in the management of critically ill patients in the ICU. Today it is possible to detect and analyze a great variety of physiological signals by various noninvasive and invasive techniques. An intensivist should be able to select and perform the most appropriate monitoring method for the individual patient considering risk-benefit ratio of the particular monitoring technique and the need for immediate therapy, specific diagnosis, continuous monitoring and evaluation of morphology should be included. Despite rapid development of noninvasive monitoring techniques, invasive hemodynamic monitoring in still one of the most basic ICU procedures. It enables monitoring of pressures, flow and saturation, pressures in the systemic and pulmonary circulation, estimation of cardiac performance and judgment of the adequacy of the cardiocirculatory system. Carefully and correctly obtained information are basis for proper hemodynamic assessment which usually effects the therapeutic decisions.

Central hemodynamic responses during serial exercise tests in heart failure patients using implantable hemodynamic monitors.

Science.gov (United States)

Ohlsson, A; Steinhaus, D; Kjellström, B; Ryden, L; Bennett, T

2003-06-01

Exercise testing is commonly used in patients with congestive heart failure for diagnostic and prognostic purposes. Such testing may be even more valuable if invasive hemodynamics are acquired. However, this will make the test more complex and expensive and only provides information from isolated moments. We studied serial exercise tests in heart failure patients with implanted hemodynamic monitors allowing recording of central hemodynamics. Twenty-one NYHA Class II-III heart failure patients underwent maximal exercise tests and submaximal bike or 6-min hall walk tests to quantify their hemodynamic responses and to study the feasibility of conducting exercise tests in patients with such devices. Patients were followed for 2-3 years with serial exercise tests. During maximal tests (n=70), heart rate increased by 52+/-19 bpm while S(v)O(2) decreased by 35+/-10% saturation units. RV systolic and diastolic pressure increased 29+/-11 and 11+/-6 mmHg, respectively, while pulmonary artery diastolic pressure increased 21+/-8 mmHg. Submaximal bike (n=196) and hall walk tests (n=172) resulted in S(v)O(2) changes of 80 and 91% of the maximal tests, while RV pressures ranged from 72 to 79% of maximal responses. An added potential value of implantable hemodynamic monitors in heart failure patients may be to quantitatively determine the true hemodynamic profile during standard non-invasive clinical exercise tests and to compare that to hemodynamic effects of regular exercise during daily living. It would be of interest to study whether such information could improve the ability to predict changes in a patient's clinical condition and to improve tailoring patient management.

Venous hemodynamic changes in lower limb venous disease

DEFF Research Database (Denmark)

Lee, Byung Boong; Nicolaides, Andrew N; Myers, Kenneth

2016-01-01

). Their aim was to confirm or dispel long-held hemodynamic principles and to provide a comprehensive review of venous hemodynamic concepts underlying the pathophysiology of lower limb venous disorders, their usefulness for investigating patients and the relevant hemodynamic changes associated with various...... forms of treatment. Chapter 1 is devoted to basic hemodynamic concepts and normal venous physiology. Chapter 2 presents the mechanism and magnitude of hemodynamic changes in acute deep vein thrombosis indicating their pathophysiological and clinical significance. Chapter 3 describes the hemodynamic...... changes that occur in different classes of chronic venous disease and their relation to the anatomic extent of disease in the macrocirculation and microcirculation. The next four chapters (Chapters 4-7) describe the hemodynamic changes resulting from treatment by compression using different materials...

Reliability of oscillometric central hemodynamic responses to an orthostatic challenge

OpenAIRE

Stoner, Lee; Bonner, Chantel; Credeur, Daniel; Lambrick, Danielle; Faulkner, James; Wadsworth, Daniel; Williams, Michelle A.

2015-01-01

BackgroundMonitoring central hemodynamic responses to an orthostatic challenge may provide important insight into autonomic nervous system function. Oscillometric pulse wave analysis devices have recently emerged, presenting clinically viable options for investigating central hemodynamic properties. The purpose of the current study was to determine whether oscillometric pulse wave analysis can be used to reliably (between-day) assess central blood pressure and central pressure augmentation (a...

Hypertrophic response to hemodynamic overload: role of load vs. renin-angiotensin system activation

Science.gov (United States)

Koide, M.; Carabello, B. A.; Conrad, C. C.; Buckley, J. M.; DeFreyte, G.; Barnes, M.; Tomanek, R. J.; Wei, C. C.; Dell'Italia, L. J.; Cooper, G. 4th;

Natriuretic peptides and cerebral hemodynamics

DEFF Research Database (Denmark)

Guo, Song; Barringer, Filippa; Zois, Nora Elisabeth

2014-01-01

Natriuretic peptides have emerged as important diagnostic and prognostic tools for cardiovascular disease. Plasma measurement of the bioactive peptides as well as precursor-derived fragments is a sensitive tool in assessing heart failure. In heart failure, the peptides are used as treatment...... in decompensated disease. In contrast, their biological effects on the cerebral hemodynamics are poorly understood. In this mini-review, we summarize the hemodynamic effects of the natriuretic peptides with a focus on the cerebral hemodynamics. In addition, we will discuss its potential implications in diseases...... where alteration of the cerebral hemodynamics plays a role such as migraine and acute brain injury including stroke. We conclude that a possible role of the peptides is feasible as evaluated from animal and in vitro studies, but more research is needed in humans to determine the precise response...

Intraoperative brain hemodynamic response assessment with real-time hyperspectral optical imaging (Conference Presentation)

Science.gov (United States)

Laurence, Audrey; Pichette, Julien; Angulo-Rodríguez, Leticia M.; Saint Pierre, Catherine; Lesage, Frédéric; Bouthillier, Alain; Nguyen, Dang Khoa; Leblond, Frédéric

2016-03-01

Following normal neuronal activity, there is an increase in cerebral blood flow and cerebral blood volume to provide oxygenated hemoglobin to active neurons. For abnormal activity such as epileptiform discharges, this hemodynamic response may be inadequate to meet the high metabolic demands. To verify this hypothesis, we developed a novel hyperspectral imaging system able to monitor real-time cortical hemodynamic changes during brain surgery. The imaging system is directly integrated into a surgical microscope, using the white-light source for illumination. A snapshot hyperspectral camera is used for detection (4x4 mosaic filter array detecting 16 wavelengths simultaneously). We present calibration experiments where phantoms made of intralipid and food dyes were imaged. Relative concentrations of three dyes were recovered at a video rate of 30 frames per second. We also present hyperspectral recordings during brain surgery of epileptic patients with concurrent electrocorticography recordings. Relative concentration maps of oxygenated and deoxygenated hemoglobin were extracted from the data, allowing real-time studies of hemodynamic changes with a good spatial resolution. Finally, we present preliminary results on phantoms obtained with an integrated spatial frequency domain imaging system to recover tissue optical properties. This additional module, used together with the hyperspectral imaging system, will allow quantification of hemoglobin concentrations maps. Our hyperspectral imaging system offers a new tool to analyze hemodynamic changes, especially in the case of epileptiform discharges. It also offers an opportunity to study brain connectivity by analyzing correlations between hemodynamic responses of different tissue regions.

Measurement system for an in-vitro characterization of the biomechanics and hemodynamics of arterial bifurcations

International Nuclear Information System (INIS)

Suárez-Bagnasco, D; Balay, G; Negreira, C A; Cymberknop, L; Armentano, R L

2013-01-01

Arterial behaviour in-vivo is influenced, amongst other factors, by the interaction between blood flow and the arterial wall endothelium, and the biomechanical properties of the arterial wall. This interaction plays an important role in pathogenic mechanisms of cardiovascular diseases such as atherosclerosis and arteriosclerosis. To quantify these interactions both from biomechanical and hemodynamical standpoints, a complete characterization and modelling of the arterial wall, blood flow, shear wall and circumferential wall stresses are needed. The development of a new multi-parameter measurement system (distances, pressures, flows, velocity profiles, temperature, viscosity) for an in-vitro characterization of the biomechanics and hemodynamics in arterial bifurcations (specially in carotid bifurcations) is described. This set-up represents an improvement relative to previous set-ups developed by the group FCIEN-FMED and is presently under development. Main subsystems interactions and environment-system interactions were identified and compensated to improve system's performance. Several interesting problems related with signal acquisition using a variety of sensors and some experimental results are shown and briefly discussed. Experimental data allow construction of meshes and parameter estimation of the biomechanical properties of the arterial wall, as well as boundary conditions, all suitable to be employed in CFD and FSI numerical simulation.

Design of feedback control systems for unstable plants with saturating actuators

Science.gov (United States)

Kapasouris, Petros; Athans, Michael; Stein, Gunter

1988-01-01

A new control design methodology is introduced for multi-input/multi-output systems with unstable open loop plants and saturating actuators. A control system is designed using well known linear control theory techniques and then a reference prefilter is introduced so that when the references are sufficiently small, the control system operates linearly as designated. For signals large enough to cause saturations, the control law is modified in such a way to ensure stability and to preserve, to the extent possible, the behavior of the linear control design. Key benefits of this methodology are: the modified feedback system never produces saturating control signals, integrators and/or slow dynamics in the compensator never windup, the directionaL properties of the controls are maintained, and the closed loop system has certain guaranteed stability properties. The advantages of the new design methodology are illustrated in the simulation of an approximation of the AFTI-16 (Advanced Fighter Technology Integration) aircraft multivariable longitudinal dynamics.

Clinical, morphological, and hemodynamic independent characteristic factors for rupture of posterior communicating artery aneurysms.

Science.gov (United States)

Zhang, Ying; Jing, Linkai; Liu, Jian; Li, Chuanhui; Fan, Jixing; Wang, Shengzhang; Li, Haiyun; Yang, Xinjian

2016-08-01

To identify clinical, morphological, and hemodynamic independent characteristic factors that discriminate posterior communicating artery (PCoA) aneurysm rupture status. 173 patients with single PCoA aneurysms (108 ruptured, 65 unruptured) between January 2012 and June 2014 were retrospectively collected. Patient-specific models based on their three-dimensional digital subtraction angiography images were constructed and analyzed by a computational fluid dynamic method. All variables were analyzed by univariate analysis and multivariate logistic regression analysis. Two clinical factors (younger age and atherosclerosis), three morphological factors (higher aspect ratio, bifurcation type, and irregular shape), and six hemodynamic factors (lower mean and minimum wall shear stress, higher oscillatory shear index, a greater portion of area under low wall shear stress, unstable and complex flow pattern) were significantly associated with PCoA aneurysm rupture. Independent factors characterizing the rupture status were identified as age (OR 0.956, p=0.015), irregular shape (OR 6.709, pPCoA aneurysm rupture were younger age, irregular shape, and low minimum wall shear stress. This may be useful for guiding risk assessments and subsequent treatment decisions for PCoA aneurysms. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Low frequency noise in the unstable contact region of Au-to-Au microcontact for microelectromechanical system switches

Science.gov (United States)

Qiu, Haodong; Wang, Hong; Ke, Feixiang

2014-06-01

The noise behavior of Au-to-Au microcontact for microelectromechanical system switches has been experimentally studied in the unstable contact region. The results suggest that the electrical conduction remains nonmetallic at the initial stage during contact formation due to the existence of alien films, and traps in the alien layer located at the contact interface could play an important role in determining the conduction noise. The conduction fluctuation induced by electron trapping-detrapping associated with the hydrocarbon layer is found to be an intrinsic noise source contributing to the low frequency noise in the unstable contact region.

Low frequency noise in the unstable contact region of Au-to-Au microcontact for microelectromechanical system switches

Energy Technology Data Exchange (ETDEWEB)

Qiu, Haodong; Wang, Hong, E-mail: ewanghong@ntu.edu.sg [NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Ke, Feixiang [Temasek Laboratories at Nanyang Technological University, Research Techno Plaza, Singapore 637553 (Singapore)

2014-06-23

The noise behavior of Au-to-Au microcontact for microelectromechanical system switches has been experimentally studied in the unstable contact region. The results suggest that the electrical conduction remains nonmetallic at the initial stage during contact formation due to the existence of alien films, and traps in the alien layer located at the contact interface could play an important role in determining the conduction noise. The conduction fluctuation induced by electron trapping-detrapping associated with the hydrocarbon layer is found to be an intrinsic noise source contributing to the low frequency noise in the unstable contact region.

Low frequency noise in the unstable contact region of Au-to-Au microcontact for microelectromechanical system switches

International Nuclear Information System (INIS)

Qiu, Haodong; Wang, Hong; Ke, Feixiang

2014-01-01

The noise behavior of Au-to-Au microcontact for microelectromechanical system switches has been experimentally studied in the unstable contact region. The results suggest that the electrical conduction remains nonmetallic at the initial stage during contact formation due to the existence of alien films, and traps in the alien layer located at the contact interface could play an important role in determining the conduction noise. The conduction fluctuation induced by electron trapping-detrapping associated with the hydrocarbon layer is found to be an intrinsic noise source contributing to the low frequency noise in the unstable contact region.

Inverse problems in 1D hemodynamics on systemic networks: a sequential approach.

Science.gov (United States)

Lombardi, D

2014-02-01

In this work, a sequential approach based on the unscented Kalman filter is applied to solve inverse problems in 1D hemodynamics, on a systemic network. For instance, the arterial stiffness is estimated by exploiting cross-sectional area and mean speed observations in several locations of the arteries. The results are compared with those ones obtained by estimating the pulse wave velocity and the Moens-Korteweg formula. In the last section, a perspective concerning the identification of the terminal models parameters and peripheral circulation (modeled by a Windkessel circuit) is presented. Copyright © 2013 John Wiley & Sons, Ltd.

The hemodynamic repercussions of the autonomic modulations in ...

African Journals Online (AJOL)

Igor Victorovich Lakhno

2017-01-16

Jan 16, 2017 ... autonomic balance, arterial and venous hemodynamic Doppler indices and CTG variables in case of nor- mal fetal ... score of decelerations. Results: The .... puter electrocardiographic system ''Cardiolab Baby Card” (Scien-.

UNSTABLE PLANETARY SYSTEMS EMERGING OUT OF GAS DISKS

International Nuclear Information System (INIS)

Matsumura, Soko; Thommes, Edward W.; Chatterjee, Sourav; Rasio, Frederic A.

2010-01-01

The discovery of over 400 extrasolar planets allows us to statistically test our understanding of the formation and dynamics of planetary systems via numerical simulations. Traditional N-body simulations of multiple-planet systems without gas disks have successfully reproduced the eccentricity (e) distribution of the observed systems by assuming that the planetary systems are relatively closely packed when the gas disk dissipates, so that they become dynamically unstable within the stellar lifetime. However, such studies cannot explain the small semimajor axes a of extrasolar planetary systems, if planets are formed, as the standard planet formation theory suggests, beyond the ice line. In this paper, we numerically study the evolution of three-planet systems in dissipating gas disks, and constrain the initial conditions that reproduce the observed a and e distributions simultaneously. We adopt initial conditions that are motivated by the standard planet formation theory, and self-consistently simulate the disk evolution and planet migration, by using a hybrid N-body and one-dimensional gas disk code. We also take into account eccentricity damping, and investigate the effect of saturation of corotation resonances on the evolution of planetary systems. We find that the a distribution is largely determined in a gas disk, while the e distribution is determined after the disk dissipation. We also find that there may be an optimum disk mass which leads to the observed a-e distribution. Our simulations generate a larger fraction of planetary systems trapped in mean-motion resonances (MMRs) than the observations, indicating that the disk's perturbation to the planetary orbits may be important to explain the observed rate of MMRs. We also find a much lower occurrence of planets on retrograde orbits than the current observations of close-in planets suggest.

[Hemodynamics, the autonomic nervous system and water metabolism as criteria for developing the general adaptation syndrome in pregnant women].

Science.gov (United States)

Gur'ianov, V A; Shepetovskaia, N L; Pivovarova, G M; Tolmachev, G N; Volodin, A V

2007-01-01

By taking into account the fact that the autonomic nervous and cardiovascular systems (ANS and CVS) are the major links of development of the general adaptation syndrome in pregnancy, which are affected by all the processes involved in the development of the syndrome, the author analyzed the state of these systems in healthy non-pregnant and pregnant women (HNPW and HPW) and in pregnant women with gestosis. HNPW were found to have already a prerequisite for impairing pregnancy adaptive processes as ANS and CVS dysfunction. In HPW, these impairments were more pronounced. In the pregnant women, impaired adaptive processes manifested themselves as excess sympathicotonia in 72% and parasympathicotonia in 23% of cases despite the treatment performed, which was accompanied by hypokinetic hemodynamics in 53 and 50%, respectively. In hyper- and eukinetic hemodynamics, there were no physiologically required decreases in total peripheral vascular resistance while in hypokinetic hemodynamics, there was its pathological increase. Such disorders enhance the significance of abdominal compartment syndrome, aortocaval compression, ischemia-reperfusion, hydrodynamic and membranogenic (capillary leakage) factors of impaired water metabolism, which contributes to adaptation derangement. Based on the findings, the authors have created a developmental modulation algorithm for the general adaptation syndrome by completed pregnancy and surgical delivery.

[Unit of hemodynamics: the production of the knowledge].

Science.gov (United States)

Linch, Graciele Fernanda da Costa; Guido, Laura de Azevedo; Pitthan, Luiza de Oliveira; Umann, Juliane

2009-12-01

This study aimed at doing an integrative review that has as objective to investigate what has been published on nursing in hemodynamic in the following data bases: Scientific Electronic Library Online (SciELO), Medical Literature Analysis and Retrieval System Online (MEDLINE), Latin American and Caribbean Health Sciences (LILACS), and Nursing Database (BDENF); with the descriptors: Enfermagem and Hemodinâmica and Nursing and Hemodynamics. The data indicate that the studies in his majority were developed by nurses, and made a list to the presence of nursing, there were still boarded aspects made a list to the reprocess of catheters and health of the professionals of nursing. Nevertheless, it is noticeable that the publication of works connected with the thematic of hemodynamic is limited. However, they demonstrate the predominance of inquiries and reports making a list to the aspects of the presence of nursing in this sector which may represent the necessities and the problems that permeate the work.

Patient-Specific Modeling of Interventricular Hemodynamics in Single Ventricle Physiology

Science.gov (United States)

Vedula, Vijay; Feinstein, Jeffrey; Marsden, Alison

2016-11-01

Single ventricle (SV) congenital heart defects, in which babies are born with only functional ventricle, lead to significant morbidity and mortality with over 30% of patients developing heart failure prior to adulthood. Newborns with SV physiology typically undergo three palliative surgeries, in which the SV becomes the systemic pumping chamber. Depending on which ventricle performs the systemic function, patients are classified as having either a single left ventricle (SLV) or a single right ventricle (SRV), with SRV patients at higher risk of failure. As the native right ventricles are not designed to meet systemic demands, they undergo remodeling leading to abnormal hemodynamics. The hemodynamic characteristics of SLVs compared with SRVs is not well established. We present a validated computational framework for performing patient-specific modeling of ventricular flows, and apply it across 6 SV patients (3SLV + 3SRV), comparing hemodynamic conditions between the two subgroups. Simulations are performed with a stabilized finite element method coupled with an immersed boundary method for modeling heart valves. We discuss identification of hemodynamic biomarkers of ventricular remodeling for early risk assessment of failure. This research is supported in part by the Stanford Child Health Research Institute and the Stanford NIH-NCATS-CTSA through Grant UL1 TR001085 and due to U.S. National Institute of Health through NIH NHLBI R01 Grants 5R01HL129727-02 and 5R01HL121754-03.

Percutaneous cardiopulmonary support for catheter ablation of unstable ventricular arrhythmias in high-risk patients.

Science.gov (United States)

Carbucicchio, Corrado; Della Bella, Paolo; Fassini, Gaetano; Trevisi, Nicola; Riva, Stefania; Giraldi, Francesco; Baratto, Francesca; Marenzi, Giancarlo; Sisillo, Erminio; Bartorelli, Antonio; Alamanni, Francesco

2009-11-01

In patients with severe cardiomyopathy, recurrent episodes of nontolerated ventricular tachycardia (VT) or electrical storm (ES) frequently cause acute heart failure and cardiac death; the suppression of the arrhythmia is therefore lifesaving, but feasibility of catheter ablation (CA) is precluded by the adverse hemodynamic conditions together with the characteristics of the arrhythmia that interdicts efficacious mapping. The use of the percutaneous cardiopulmonary support (CPS) for circulatory assistance may allow patient's stabilization and enhance efficacy and safety of CA in this emergency setting. 19 patients (19 males; mean age 61 +/- 6 years; chronic ischemic cardiomyopathy, eleven patients; primary dilated cardiomyopathy, six patients; arrhythmogenic right ventricular dysplasia/ cardiomyopathy, two patients) with recurrent nontolerated VT episodes undergoing CPS-assisted CA were retrospectively evaluated. Twelve patients had acute hemodynamic failure refractory to inotropic agents and ventilatory assistance, seven patients had undergone a failing nonconventional CA procedure. 14 patients presented with ES, and in twelve the procedure was undertaken under emergency conditions within 24 h from admission. Patients were ventilated under general anesthesia and assisted by a multidisciplinary team. The CPS system consisted in a Medtronic Bio-Medicus centrifugal pump and in a Maxima Plus oxygenator, a 15-F arterial cannula, and a 17-F venous cannula. Flows between 2 and 3 l/min were activated after induction of 56/62 forms of nontolerated VT, achieving hemodynamic stabilization in all patients. CA was mainly guided by conventional activation mapping and was effective in abolishing 45/56 supported VTs; in 10/19 patients all clinical VTs were suppressed by CA. Mean procedural time was 4 h and 20 min. Complete stabilization was achieved in 13 patients (68%) without VT recurrence during a 7-day in-hospital monitoring. A significant clinical improvement was observed in

Revealing Bell's nonlocality for unstable systems in high energy physics

Energy Technology Data Exchange (ETDEWEB)

Hiesmayr, Beatrix C.; Gabriel, Andreas; Huber, Marcus [University of Vienna, Faculty of Physics, Vienna (Austria); Di Domenico, Antonio [Sapienza Universita di Roma (Italy); INFN Sezione di Roma, Rome (Italy); Curceanu, Catalina [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Larsson, Jan-Aake [Linkoepings Universitet, Institionen foer Systemteknik, Linkoeping (Sweden); Moskal, Pawel [Jagiellonian University, Institute of Physics, Cracow (Poland)

2012-01-15

Entanglement and its consequences - in particular the violation of Bell inequalities, which defies our concepts of realism and locality - have been proven to play key roles in Nature by many experiments for various quantum systems. Entanglement can also be found in systems not consisting of ordinary matter and light, i.e. in massive meson-antimeson systems. Bell inequalities have been discussed for these systems, but up to date no direct experimental test to conclusively exclude local realism was found. This mainly stems from the fact that one only has access to a restricted class of observables and that these systems are also decaying. In this Letter we put forward a Bell inequality for unstable systems which can be tested at accelerator facilities with current technology. Herewith, the long awaited proof that such systems at different energy scales can reveal the sophisticated ''dynamical'' nonlocal feature of Nature in a direct experiment gets feasible. Moreover, the role of entanglement and CP violation, an asymmetry between matter and antimatter, is explored, a special feature offered only by these meson-antimeson systems. (orig.)

[Hemodynamic changes in hypoglycemic shock].

Science.gov (United States)

Gutiérrez, C; Piza, R; Chousleb, A; Hidalgo, M A; Ortigosa, J L

1977-01-01

Severe hypoglycemia may be present in seriously ill patients; if it is not corrected opportunely a series of neuroendocrinal mechanisms take place aimed at correcting metabolic alterations. These mechanisms can produce hemodynamic alterations as well. Nine mongrel dogs were studied with continuous registration of: blood pressure, central venous pressure, cardiac frequency, respiratory frequency, electrocardiogram and first derivative (Dp/Dt). Six dogs received crystalline (fast acting) insuline intravenously (group 1). After hemodynamic changes were registered hypoglycemia was corrected with 50 per cent glucose solution. Complementary insuline doses were administered to three dogs (group 2); in this group hypoglycemia was not corrected. In group 1 during hypoglycemia there was an increase in blood pressure, central venous pressure, cardiac frequency, respiratory frequency and Dp/Dt, and changes in QT and T wave on the EKG; these changes were partially reversible after hypoglycemia was corrected. The above mentioned alterations persisted in group 2, breathing became irregular irregular and respiratory arrest supervened. It can be inferred that the hemodynamic response to hypoglycemia is predominantly adrenergic. The role of catecolamines, glucocorticoides, glucagon, insuline, cyclic AMP in metabolic and hemodynamic alterations consecutive to hypoglycemia are discussed.

Childhood moyamoya disease: hemodynamic MRI

International Nuclear Information System (INIS)

Tzika, A.A.; Robertson, R.L.; Barnes, P.D.; Vajapeyam, S.; Burrows, P.E.; Treves, S.T.; Scott, R.M. I

1997-01-01

Background. Childhood moyamoya disease is a rare progressive cerebrovascular disease. Objective. To evaluate cerebral hemodynamics using dynamic Gd-DTPA-enhanced imaging in children with moyamoya disease. Materials and methods. Eight children (2-11 years of age) with the clinical and angiographic findings typical of moyamoya disease, before and/or after surgical intervention (pial synangiosis), underwent conventional MR imaging (MRI) and hemodynamic MR imaging (HMRI). HMRI used a spoiled gradient-echo with low flip angle (10 deg) and long TE (TR/TE = 24/15 ms) to minimize T 1 effects and emphasize T 2 * weighting. Raw and calculated hemodynamic images were reviewed. Three-dimensional time-of-flight MR angiography (MRA) and perfusion brain single photon emission computed tomography (SPECT) were also performed. Results. Abnormal hemodynamic maps resulting from vascular stenosis or occlusion and basal collaterals were observed in six patient studies. HMRI depicted perfusion dynamics of affected cerebrovascular territories, detected cortical perfusion deficits, and complemented conventional MRI and MRA. HMRI findings were consistent with those of catheter angiography and perfusion SPECT. Conclusion. Our preliminary experience suggests that HMRI may be of value in the preoperative and postoperative evaluation of surgical interventions in moyamoya disease. (orig.). With 4 figs., 3 tabs

Spontaneous hemodynamic oscillations during human sleep and sleep stage transitions characterized with near-infrared spectroscopy.

Directory of Open Access Journals (Sweden)

Tiina Näsi

Full Text Available Understanding the interaction between the nervous system and cerebral vasculature is fundamental to forming a complete picture of the neurophysiology of sleep and its role in maintaining physiological homeostasis. However, the intrinsic hemodynamics of slow-wave sleep (SWS are still poorly known. We carried out 30 all-night sleep measurements with combined near-infrared spectroscopy (NIRS and polysomnography to investigate spontaneous hemodynamic behavior in SWS compared to light (LS and rapid-eye-movement sleep (REM. In particular, we concentrated on slow oscillations (3-150 mHz in oxy- and deoxyhemoglobin concentrations, heart rate, arterial oxygen saturation, and the pulsation amplitude of the photoplethysmographic signal. We also analyzed the behavior of these variables during sleep stage transitions. The results indicate that slow spontaneous cortical and systemic hemodynamic activity is reduced in SWS compared to LS, REM, and wakefulness. This behavior may be explained by neuronal synchronization observed in electrophysiological studies of SWS and a reduction in autonomic nervous system activity. Also, sleep stage transitions are asymmetric, so that the SWS-to-LS and LS-to-REM transitions, which are associated with an increase in the complexity of cortical electrophysiological activity, are characterized by more dramatic hemodynamic changes than the opposite transitions. Thus, it appears that while the onset of SWS and termination of REM occur only as gradual processes over time, the termination of SWS and onset of REM may be triggered more abruptly by a particular physiological event or condition. The results suggest that scalp hemodynamic changes should be considered alongside cortical hemodynamic changes in NIRS sleep studies to assess the interaction between the autonomic and central nervous systems.

A unified double-loop multi-scale control strategy for NMP integrating-unstable systems

International Nuclear Information System (INIS)

Seer, Qiu Han; Nandong, Jobrun

2016-01-01

This paper presents a new control strategy which unifies the direct and indirect multi-scale control schemes via a double-loop control structure. This unified control strategy is proposed for controlling a class of highly nonminimum-phase processes having both integrating and unstable modes. This type of systems is often encountered in fed-batch fermentation processes which are very difficult to stabilize via most of the existing well-established control strategies. A systematic design procedure is provided where its applicability is demonstrated via a numerical example. (paper)

Invasive hemodynamic monitoring in the postoperative period of cardiac surgery

Directory of Open Access Journals (Sweden)

Desanka Dragosavac

1999-08-01

Full Text Available OBJETIVE: To assess the hemodynamic profile of cardiac surgery patients with circulatory instability in the early postoperative period (POP. METHODS: Over a two-year period, 306 patients underwent cardiac surgery. Thirty had hemodynamic instability in the early POP and were monitored with the Swan-Ganz catheter. The following parameters were evaluated: cardiac index (CI, systemic and pulmonary vascular resistance, pulmonary shunt, central venous pressure (CVP, pulmonary capillary wedge pressure (PCWP, oxygen delivery and consumption, use of vasoactive drugs and of circulatory support. RESULTS: Twenty patients had low cardiac index (CI, and 10 had normal or high CI. Systemic vascular resistance was decreased in 11 patients. There was no correlation between oxygen delivery (DO2 and consumption (VO2, p=0.42, and no correlation between CVP and PCWP, p=0.065. Pulmonary vascular resistance was decreased in 15 patients and the pulmonary shunt was increased in 19. Two patients with CI < 2L/min/m² received circulatory support. CONCLUSION: Patients in the POP of cardiac surgery frequently have a mixed shock due to the systemic inflammatory response syndrome (SIRS. Therefore, invasive hemodynamic monitoring is useful in handling blood volume, choice of vasoactive drugs, and indication for circulatory support.

A study of unstable rock failures using finite difference and discrete element methods

Science.gov (United States)

Garvey, Ryan J.

Case histories in mining have long described pillars or faces of rock failing violently with an accompanying rapid ejection of debris and broken material into the working areas of the mine. These unstable failures have resulted in large losses of life and collapses of entire mine panels. Modern mining operations take significant steps to reduce the likelihood of unstable failure, however eliminating their occurrence is difficult in practice. Researchers over several decades have supplemented studies of unstable failures through the application of various numerical methods. The direction of the current research is to extend these methods and to develop improved numerical tools with which to study unstable failures in underground mining layouts. An extensive study is first conducted on the expression of unstable failure in discrete element and finite difference methods. Simulated uniaxial compressive strength tests are run on brittle rock specimens. Stable or unstable loading conditions are applied onto the brittle specimens by a pair of elastic platens with ranging stiffnesses. Determinations of instability are established through stress and strain histories taken for the specimen and the system. Additional numerical tools are then developed for the finite difference method to analyze unstable failure in larger mine models. Instability identifiers are established for assessing the locations and relative magnitudes of unstable failure through measures of rapid dynamic motion. An energy balance is developed which calculates the excess energy released as a result of unstable equilibria in rock systems. These tools are validated through uniaxial and triaxial compressive strength tests and are extended to models of coal pillars and a simplified mining layout. The results of the finite difference simulations reveal that the instability identifiers and excess energy calculations provide a generalized methodology for assessing unstable failures within potentially complex

Unstable periodic orbits and chaotic economic growth

International Nuclear Information System (INIS)

Ishiyama, K.; Saiki, Y.

2005-01-01

We numerically find many unstable periodic solutions embedded in a chaotic attractor in a macroeconomic growth cycle model of two countries with different fiscal policies, and we focus on a special type of the unstable periodic solutions. It is confirmed that chaotic behavior represented by the model is qualitatively and quantitatively related to the unstable periodic solutions. We point out that the structure of a chaotic solution is dissolved into a class of finite unstable periodic solutions picked out among a large number of periodic solutions. In this context it is essential for the unstable periodic solutions to be embedded in the chaotic attractor

Childhood moyamoya disease: hemodynamic MRI

Energy Technology Data Exchange (ETDEWEB)

Tzika, A.A. [Department of Radiology, Children`s Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115 (United States); Robertson, R.L. [Department of Radiology, Children`s Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115 (United States); Barnes, P.D. [Department of Radiology, Children`s Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115 (United States); Vajapeyam, S. [Department of Radiology, Children`s Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115 (United States); Burrows, P.E. [Department of Radiology, Children`s Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115 (United States); Treves, S.T. [Department of Radiology, Children`s Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115 (United States); Scott, R.M. l [Department of Radiology, Children`s Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115 (United States)

1997-09-01

Background. Childhood moyamoya disease is a rare progressive cerebrovascular disease. Objective. To evaluate cerebral hemodynamics using dynamic Gd-DTPA-enhanced imaging in children with moyamoya disease. Materials and methods. Eight children (2-11 years of age) with the clinical and angiographic findings typical of moyamoya disease, before and/or after surgical intervention (pial synangiosis), underwent conventional MR imaging (MRI) and hemodynamic MR imaging (HMRI). HMRI used a spoiled gradient-echo with low flip angle (10 deg) and long TE (TR/TE = 24/15 ms) to minimize T 1 effects and emphasize T 2{sup *} weighting. Raw and calculated hemodynamic images were reviewed. Three-dimensional time-of-flight MR angiography (MRA) and perfusion brain single photon emission computed tomography (SPECT) were also performed. Results. Abnormal hemodynamic maps resulting from vascular stenosis or occlusion and basal collaterals were observed in six patient studies. HMRI depicted perfusion dynamics of affected cerebrovascular territories, detected cortical perfusion deficits, and complemented conventional MRI and MRA. HMRI findings were consistent with those of catheter angiography and perfusion SPECT. Conclusion. Our preliminary experience suggests that HMRI may be of value in the preoperative and postoperative evaluation of surgical interventions in moyamoya disease. (orig.). With 4 figs., 3 tabs.

Acute hemodynamic response to vasodilators in primary pulmonary hypertension.

Directory of Open Access Journals (Sweden)

Kulkarni H

1996-01-01

Full Text Available Acute hemodynamic effects of high flow oxygen (O2 inhalation, sublingual isosorbide dinitrate (ISDN, intravenous aminophylline (AMN and sublingual nifedipine (NIF were studied in 32 patients with primary pulmonary hypertension (PPH. In 30 out of 32 patients the basal ratio of pulmonary to systemic vascular resistance (Rp/Rs was > 0.5 (mean = 0.77 +/- 0.20. Oxygen caused significant decrease in the mean resistance ratio to 0.68 +/- 0.20 (p = 0.005. ISDN, AMN and NIF caused increase in the resistance ratio to 0.79 +/- 0.26; 0.78 +/- 0.26; and 0.80 +/- 0.23 respectively. O2, ISDN, AMN and NIF caused a fall of Rp/Rs in 21 (65.6%, 10 (31.2%, 10(31.2% and 9(28.1% patients respectively. Thus, of the four drugs tested high flow O2 inhalation resulted in fall of Rp/Rs in two thirds of patients whereas ISDN, AMN and NIF caused a mean rise in Rp/Rs. One third of patients did respond acutely to the latter three drugs. Acute hemodynamic studies are useful before prescribing vasodilators in patients with PPH since more of the commonly used drugs like ISDN, AMN, NIF could have detrimental hemodynamic responses in some patients. However, great caution should be exercised before performing hemodynamic study as the procedure has definite mortality and morbidity.

Dynamical formation of a hairy black hole in a cavity from the decay of unstable solitons

International Nuclear Information System (INIS)

Sanchis-Gual, Nicolas; Font, José A; Carlos Degollado, Juan; Herdeiro, Carlos; Radu, Eugen

2017-01-01

Recent numerical relativity simulations within the Einstein–Maxwell–(charged-)Klein–Gordon (EMcKG) system have shown that the non-linear evolution of a superradiantly unstable Reissner–Nordström black hole (BH) enclosed in a cavity, leads to the formation of a BH with scalar hair. Perturbative evidence for the stability of such hairy BHs has been independently established, confirming they are the true endpoints of superradiant instability. The same EMcKG system admits also charged scalar soliton-type solutions, which can be either stable or unstable. Using numerical relativity techniques, we provide evidence that the time evolution of some of these unstable solitons leads, again, to the formation of a hairy BH. In some other cases, unstable solitons evolve into a (bald) Reissner–Nordström BH. These results establish that the system admits two distinct channels to form hairy BHs at the threshold of superradiance: growing hair from an unstable (bald) BH, or growing a horizon from an unstable (horizonless) soliton. Some parallelism with the case of asymptotically flat boson stars and Kerr BHs with scalar hair is drawn. (paper)

Dynamical formation of a hairy black hole in a cavity from the decay of unstable solitons

Science.gov (United States)

Sanchis-Gual, Nicolas; Degollado, Juan Carlos; Font, José A.; Herdeiro, Carlos; Radu, Eugen

2017-08-01

Recent numerical relativity simulations within the Einstein-Maxwell-(charged-)Klein-Gordon (EMcKG) system have shown that the non-linear evolution of a superradiantly unstable Reissner-Nordström black hole (BH) enclosed in a cavity, leads to the formation of a BH with scalar hair. Perturbative evidence for the stability of such hairy BHs has been independently established, confirming they are the true endpoints of superradiant instability. The same EMcKG system admits also charged scalar soliton-type solutions, which can be either stable or unstable. Using numerical relativity techniques, we provide evidence that the time evolution of some of these unstable solitons leads, again, to the formation of a hairy BH. In some other cases, unstable solitons evolve into a (bald) Reissner-Nordström BH. These results establish that the system admits two distinct channels to form hairy BHs at the threshold of superradiance: growing hair from an unstable (bald) BH, or growing a horizon from an unstable (horizonless) soliton. Some parallelism with the case of asymptotically flat boson stars and Kerr BHs with scalar hair is drawn.

Unstable oscillatory Pierce modes of neutralized electron beams

International Nuclear Information System (INIS)

Cary, J.R.; Lemons, D.S.

1982-01-01

Oscillatory modes of the Pierce system have been calculated. These modes are found to have growth rates comparable to the previously investigated purely growing modes. When these modes are included, it is found that the Pierce system is unstable for most values of ω/sub p/ L/V 0 >π

Occupational exposure in hemodynamic; Exposicao ocupacional em hemodinamica

Energy Technology Data Exchange (ETDEWEB)

Silva, Amanda J.; Fernandes, Ivani M.; Silva, Paula P. Nou; Sordi, Gian Maria A.A.; Carneiro, Janete C.G.G., E-mail: ajsilva@ipen.b, E-mail: imfernandes@ipen.b, E-mail: ppsilva@ipen.b, E-mail: gmsordi@ipen.b, E-mail: janetegc@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2011-10-26

This paper has an objective to perform a radiometric survey at a hemodynamic service. Besides, it was intended to evaluate the effective dose of health professionals and to provide data which can contribute with minimization of exposures during the realization of hemodynamic procedure. The radiometric survey was realized in the real environment of work simulating the conditions of a hemodynamic study with a ionization chamber

Joint state and parameter estimation for a class of cascade systems: Application to a hemodynamic model

KAUST Repository

Zayane, Chadia

2014-06-01

In this paper, we address a special case of state and parameter estimation, where the system can be put on a cascade form allowing to estimate the state components and the set of unknown parameters separately. Inspired by the nonlinear Balloon hemodynamic model for functional Magnetic Resonance Imaging problem, we propose a hierarchical approach. The system is divided into two subsystems in cascade. The state and input are first estimated from a noisy measured signal using an adaptive observer. The obtained input is then used to estimate the parameters of a linear system using the modulating functions method. Some numerical results are presented to illustrate the efficiency of the proposed method.

Ionizing radiation occupational exposure in the hemodynamics services

International Nuclear Information System (INIS)

Gronchi, Claudia Carla

2004-01-01

The purpose of this research is to study the ionizing radiation occupational exposure in the hemodynamic services of two large scale hospitals (Hospital A and Hospital B) of the Sao Paulo city. The research looked into annual doses that 279 professionals of the hemodynamic services were exposed to between 1991 and 2002. The data analyzed was collected from the database of the Instituto de Pesquisas Energeticas e Nucleares (IPEN) for Hospital A, and from the Radiological Protection Department of Hospital B. Besides this, measures of hands and crystalline lens equivalent doses were performed during hemodynamic procedures of the physicians, assistant physicians and nursing assistants with TL dosimeters (CaSO 4 :Dy + Teflon R) produced at IPEN. The safety procedures adopted by the hospitals were verified with the aid of a specific questionnaire for the hemodynamic services. Finally, a profile of the professionals that work in cardiac catheterism laboratories of the hemodynamic services was delineated, considering the variables of individual monitoring time, age and sex. This study allowed for observation of the behavior of the professionals' annual doses of these hemodynamic services in relation to the Comissao Nacional de Energia Nuclear and the Secretaria de Vigilancia Sanitaria limits. It showed that the annual doses of the same specialized occupations would vary from one hospital to another. It further showed the need of individual monitoring of the physicians' unprotected body parts (hands and crystalline lens) during the hemodynamic procedures. (author)

Hemodynamic Effects of Glucagon - A Literature Review

DEFF Research Database (Denmark)

Meidahl Petersen, Kasper; Bøgevig, Søren; Holst, Jens Juul

2018-01-01

Context: Glucagon's effects on hemodynamic parameters - most notably heart rate and cardiac contractility - are overlooked. The glucagon receptor is a central target in novel and anticipated type 2 diabetes therapies and hemodynamic consequences of glucagon signaling have therefore become increas...

A genetic fuzzy system for unstable angina risk assessment.

Science.gov (United States)

Dong, Wei; Huang, Zhengxing; Ji, Lei; Duan, Huilong

2014-02-18

Unstable Angina (UA) is widely accepted as a critical phase of coronary heart disease with patients exhibiting widely varying risks. Early risk assessment of UA is at the center of the management program, which allows physicians to categorize patients according to the clinical characteristics and stratification of risk and different prognosis. Although many prognostic models have been widely used for UA risk assessment in clinical practice, a number of studies have highlighted possible shortcomings. One serious drawback is that existing models lack the ability to deal with the intrinsic uncertainty about the variables utilized. In order to help physicians refine knowledge for the stratification of UA risk with respect to vagueness in information, this paper develops an intelligent system combining genetic algorithm and fuzzy association rule mining. In detail, it models the input information's vagueness through fuzzy sets, and then applies a genetic fuzzy system on the acquired fuzzy sets to extract the fuzzy rule set for the problem of UA risk assessment. The proposed system is evaluated using a real data-set collected from the cardiology department of a Chinese hospital, which consists of 54 patient cases. 9 numerical patient features and 17 categorical patient features that appear in the data-set are selected in the experiments. The proposed system made the same decisions as the physician in 46 (out of a total of 54) tested cases (85.2%). By comparing the results that are obtained through the proposed system with those resulting from the physician's decision, it has been found that the developed model is highly reflective of reality. The proposed system could be used for educational purposes, and with further improvements, could assist and guide young physicians in their daily work.

Hemodynamic Perturbations in Deep Brain Stimulation Surgery: First Detailed Description

Directory of Open Access Journals (Sweden)

Tumul Chowdhury

2017-08-01

Full Text Available Background: Hemodynamic perturbations can be anticipated in deep brain stimulation (DBS surgery and may be attributed to multiple factors. Acute changes in hemodynamics may produce rare but severe complications such as intracranial bleeding, transient ischemic stroke and myocardium infarction. Therefore, this retrospective study attempts to determine the incidence of hemodynamic perturbances (rate and related risk factors in patients undergoing DBS surgery.Materials and Methods: After institutional approval, all patients undergoing DBS surgery for the past 10 years were recruited for this study. Demographic characteristics, procedural characteristics and intraoperative hemodynamic changes were noted. Event rate was calculated and the effect of all the variables on hemodynamic perturbations was analyzed by regression model.Results: Total hemodynamic adverse events during DBS surgery was 10.8 (0–42 and treated in 57% of cases.Conclusion: Among all the perioperative variables, the baseline blood pressure including systolic, diastolic, and mean arterial pressure was found to have highly significant effect on these intraoperative hemodynamic perturbations.

On the representations of Poincare group associated with unstable particles

International Nuclear Information System (INIS)

Exner, RP.

1983-01-01

The problem of relativistically-covariant description of unstable particles is reexamined. We follow the approach which associates a unitary reducible representation of Poincare group with a larger isolated system, and compare it with the one ascribing a non-unitary irreducible representation to the unstable particle alone. It is shown that the problem roots in choice of the subspace Hsub(u) of the state Hilbert space which could be related to the unstable particle. Translational invariance of Hsub(u) is proved to be incompatible with unitarity of the boosts. Further we propose a concrete choice of Hsub(u) and argue that in most cases of the actual experimental arrangements, this subspace is effectively one-dimensional. A correct slow-down for decay of a moving particle is obtained

Effects of tilting on central hemodynamics and homeostatic mechanisms in cirrhosis

DEFF Research Database (Denmark)

Møller, Søren; Nørgaard, Annette; Henriksen, Jens H

2004-01-01

Patients with cirrhosis have a hyperdynamic circulation and an abnormal blood volume distribution with central hypovolemia, an activated sympathetic nervous system (SNS) as well as the renin-angiotensin-aldosterone system (RAAS). As the hyperdynamic circulation in cirrhosis may be present only...... in the supine patient, we studied the humoral and central hemodynamic responses to changes with posture. Twenty-three patients with alcoholic cirrhosis (Child-Turcotte-Pugh classes A/B/C: 2/13/8) and 14 healthy controls were entered. Measurements of central hemodynamics and activation of SNS and RAAS were taken......). Central circulation time increased only in the patients (+30% vs. -1%, P higher in the patients than in the controls (P

Cosmology and unstable nuclei

International Nuclear Information System (INIS)

Schramm, D.N.

1995-01-01

Primordial nucleosynthesis has established itself as one of the three pillars of Big Bang cosmology. Many of the Big Bang Nucleosynthesis reactions involve unstable nuclei. Hence there is a tight relationship hetween the subject of this conference and cosmology. The prime role of unstable nuclei in cosmology is related to lithium synthesis and the lack of cosmological synthesis of Be and B. These nuclei will thus be focused upon. Nucleosynthesis involves comparing calculated abundances with observed abundances. In general, abundance determinations are dominated by systematic rather than statistical errors, and work on bounding systematics is crucial. The quark-hadron inspired inhomogeneous calculations now unanimously agree that only relatively small variations in Ω b are possible vis-a-vis the homogeneous model; hence the robustness of Ω b ∼0.05 is now apparent. (These calculations depend critically on unstable nuclei.) The above argues that the bulk of the baryons in the universe are not producing visible light. A comparison with the ROSAT cluster data is also shown to be consistent with the standard BBN model. Ω b ∼1 seems to be definitely excluded, so if Ω TOTAL =1, as some recent observations may hint, then non-baryonic dark matter is required. The implications of the recently reported halo microlensing events are discussed. In summary, it is argued that the physics of unstable nuclei affects the fundamental dark matter argument. ((orig.))

Postural hemodynamic changes after turning to prone position

Directory of Open Access Journals (Sweden)

Микола Віталійович Лизогуб

2015-03-01

Full Text Available Background of study. Prone position is one of the most complex positions for anesthesiologist as it is accompanied by several physiological changes that can lead to specific complications. Hemodynamic changes are most controversial.Aim of study was to establish hemodynamic changes in non-anaesthetized patients in prone position depending on body mass index.Material and methods. We examined central hemodynamics in 40 patients the day before surgery using thoracic rheography in supine position, in prone position 5 min after turning and in prone position 20 min after turning. Patients were divided into 2 groups according to body mass index (18-25 and 26-35.Results. Patients with normal body weight did not have any hemodynamic changes after turning to prone position. Patients with increased body weight had higher cardiac index. After turning to prone position obese patients’ cardiac output and cardiac index reduced 22% comparing with supine position. After 20 min in prone position these hemodynamic parameters were found to be reduced to the same level.Conclusion. Significant hemodynamic changes after turning from supine to prone position were revealed only in patients with increased body mass index. In these patients cardiac index in prone position was reduced by 22% comparing to supine position

Lagrangian postprocessing of computational hemodynamics.

Science.gov (United States)

Shadden, Shawn C; Arzani, Amirhossein

2015-01-01

Recent advances in imaging, modeling, and computing have rapidly expanded our capabilities to model hemodynamics in the large vessels (heart, arteries, and veins). This data encodes a wealth of information that is often under-utilized. Modeling (and measuring) blood flow in the large vessels typically amounts to solving for the time-varying velocity field in a region of interest. Flow in the heart and larger arteries is often complex, and velocity field data provides a starting point for investigating the hemodynamics. This data can be used to perform Lagrangian particle tracking, and other Lagrangian-based postprocessing. As described herein, Lagrangian methods are necessary to understand inherently transient hemodynamic conditions from the fluid mechanics perspective, and to properly understand the biomechanical factors that lead to acute and gradual changes of vascular function and health. The goal of the present paper is to review Lagrangian methods that have been used in post-processing velocity data of cardiovascular flows.

Hemodynamic and tubular changes induced by contrast media.

Science.gov (United States)

Caiazza, Antonella; Russo, Luigi; Sabbatini, Massimo; Russo, Domenico

2014-01-01

The incidence of acute kidney injury induced by contrast media (CI-AKI) is the third cause of AKI in hospitalized patients. Contrast media cause relevant alterations both in renal hemodynamics and in renal tubular cell function that lead to CI-AKI. The vasoconstriction of intrarenal vasculature is the main hemodynamic change induced by contrast media; the vasoconstriction is accompanied by a cascade of events leading to ischemia and reduction of glomerular filtration rate. Cytotoxicity of contrast media causes apoptosis of tubular cells with consequent formation of casts and worsening of ischemia. There is an interplay between the negative effects of contrast media on renal hemodynamics and on tubular cell function that leads to activation of renin-angiotensin system and increased production of reactive oxygen species (ROS) within the kidney. Production of ROS intensifies cellular hypoxia through endothelial dysfunction and alteration of mechanisms regulating tubular cells transport. The physiochemical characteristics of contrast media play a critical role in the incidence of CI-AKI. Guidelines suggest the use of either isoosmolar or low-osmolar contrast media rather than high-osmolar contrast media particularly in patients at increased risk of CI-AKI. Older age, presence of atherosclerosis, congestive heart failure, chronic renal disease, nephrotoxic drugs, and diuretics may multiply the risk of CI-AKI.

Systemic Hemodynamic Atherothrombotic Syndrome and Resonance Hypothesis of Blood Pressure Variability: Triggering Cardiovascular Events.

Science.gov (United States)

Kario, Kazuomi

2016-07-01

Blood pressure (BP) exhibits different variabilities and surges with different time phases, from the shortest beat-by-beat to longest yearly changes. We hypothesized that the synergistic resonance of these BP variabilites generates an extraordinarily large dynamic surge in BP and triggers cardiovascular events (the resonance hypothesis). The power of pulses is transmitted to the peripheral sites without attenuation by the large arteries, in individuals with stiffened arteries. Thus, the effect of a BP surge on cardiovascular risk would be especially exaggerated in high-risk patients with vascular disease. Based on this concept, our group recently proposed a new theory of systemic hemodynamic atherothromboltic syndrome (SHATS), a vicious cycle of hemodynamic stress and vascular disease that advances organ damage and triggers cardiovascular disease. Clinical phenotypes of SHATS are large-artery atherothombotic diseases such as stroke, coronary artery disease, and aortic and pheripheral artery disease; small-artery diseases, and microcirculation-related disease such as vascular cognitive dysfunction, heart failure, and chronic kidney disease. The careful consideration of BP variability and vascular diseases such as SHATS, and the early detection and management of SHATS, will achieve more effective individualized cardiovascular protection. In the near future, information and communication technology-based 'anticipation medicine' predicted by the changes of individual BP values could be a promising approach to achieving zero cardiovascular events.

Reliability of oscillometric central hemodynamic responses to an orthostatic challenge.

Science.gov (United States)

Stoner, Lee; Bonner, Chantel; Credeur, Daniel; Lambrick, Danielle; Faulkner, James; Wadsworth, Daniel; Williams, Michelle A

2015-08-01

Monitoring central hemodynamic responses to an orthostatic challenge may provide important insight into autonomic nervous system function. Oscillometric pulse wave analysis devices have recently emerged, presenting clinically viable options for investigating central hemodynamic properties. The purpose of the current study was to determine whether oscillometric pulse wave analysis can be used to reliably (between-day) assess central blood pressure and central pressure augmentation (augmentation index) responses to a 5 min orthostatic challenge (modified tilt-table). Twenty healthy adults (26.4 y (SD 5.2), 55% F, 24.7 kg/m(2) (SD 3.8)) were tested on 3 different mornings in the fasted state, separated by a maximum of 7 days. Central hemodynamic variables were assessed on the left arm using an oscillometric device. Repeated measures analysis of variance indicated a significant main effect of the modified tilt-table for all central hemodynamic variables (P response to the tilt, central diastolic pressure increased by 4.5 mmHg (CI: 2.6, 6.4), central systolic blood pressure increased by 2.3 (CI: 4.4, 0.16) mmHg, and augmentation index decreased by an absolute - 5.3%, (CI: -2.7, -7.9%). The intra-class correlation coefficient values for central diastolic pressure (0.83-0.86), central systolic blood pressure (0.80-0.87) and AIx (0.79-0.82) were above the 0.75 criterion in both the supine and tilted positions, indicating excellent between-day reliability. Central hemodynamic responses to an orthostatic challenge can be assessed with acceptable between-day reliability using oscillometric pulse wave analysis. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Analysis of the Behavior of Undamped and Unstable High-Frequency Resonance in DFIG System

DEFF Research Database (Denmark)

Song, Yipeng; Blaabjerg, Frede

2017-01-01

As the wind power generation develops, the Doubly Fed Induction Generator (DFIG) based wind power system may suffer Sub Synchronous Resonance (SSR) and High Frequency Resonance (HFR) in the series and parallel compensated weak network. The principle and frequency of HFR have been discussed using...... the Bode diagram as an analysis tool. However, the HFR can be categorized into two different types: undamped HFR (which exists in steady state) and unstable HFR (which eventually results in complete instability and divergence), both of them are not investigated before. Since both the undamped HFR...

Congenital heart malformations induced by hemodynamic altering surgical interventions

Directory of Open Access Journals (Sweden)

Madeline eMidgett

2014-08-01

Full Text Available Embryonic heart formation results from a dynamic interplay between genetic and environmental factors. Blood flow during early embryonic stages plays a critical role in heart development, as interactions between flow and cardiac tissues generate biomechanical forces that modulate cardiac growth and remodeling. Normal hemodynamic conditions are essential for proper cardiac development, while altered blood flow induced by surgical manipulations in animal models result in heart defects similar to those seen in humans with congenital heart disease. This review compares the altered hemodynamics, changes in tissue properties, and cardiac defects reported after common surgical interventions that alter hemodynamics in the early chick embryo, and shows that interventions produce a wide spectrum of cardiac defects. Vitelline vein ligation and left atrial ligation decrease blood pressure and flow; and outflow tract banding increases blood pressure and flow velocities. These three surgical interventions result in many of the same cardiac defects, which indicate that the altered hemodynamics interfere with common looping, septation and valve formation processes that occur after intervention and that shape the four-chambered heart. While many similar defects develop after the interventions, the varying degrees of hemodynamic load alteration among the three interventions also result in varying incidence and severity of cardiac defects, indicating that the hemodynamic modulation of cardiac developmental processes is strongly dependent on hemodynamic load.

A data analysis method for identifying deterministic components of stable and unstable time-delayed systems with colored noise

Energy Technology Data Exchange (ETDEWEB)

Patanarapeelert, K. [Faculty of Science, Department of Mathematics, Mahidol University, Rama VI Road, Bangkok 10400 (Thailand); Frank, T.D. [Institute for Theoretical Physics, University of Muenster, Wilhelm-Klemm-Str. 9, 48149 Muenster (Germany)]. E-mail: tdfrank@uni-muenster.de; Friedrich, R. [Institute for Theoretical Physics, University of Muenster, Wilhelm-Klemm-Str. 9, 48149 Muenster (Germany); Beek, P.J. [Faculty of Human Movement Sciences and Institute for Fundamental and Clinical Human Movement Sciences, Vrije Universiteit, Van der Boechorststraat 9, 1081 BT Amsterdam (Netherlands); Tang, I.M. [Faculty of Science, Department of Physics, Mahidol University, Rama VI Road, Bangkok 10400 (Thailand)

2006-12-18

A method is proposed to identify deterministic components of stable and unstable time-delayed systems subjected to noise sources with finite correlation times (colored noise). Both neutral and retarded delay systems are considered. For vanishing correlation times it is shown how to determine their noise amplitudes by minimizing appropriately defined Kullback measures. The method is illustrated by applying it to simulated data from stochastic time-delayed systems representing delay-induced bifurcations, postural sway and ship rolling.

The fate of unstable gauge flux compactifications

Energy Technology Data Exchange (ETDEWEB)

Burgess, C P [McMaster Univ., Hamilton, ON (Canada). Dept. of Physics and Astronomy; [Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada); Parameswaran, S L [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Zavala, I [Bonn Univ. (Germany). Bethe Center for Theoretical Physics and Physikalisches Inst.

2008-12-15

Fluxes are widely used to stabilise extra dimensions, but the supporting monopolelike configurations are often unstable, particularly if they arise as gauge flux within a non-abelian gauge sector. We here seek the endpoint geometries to which this instability leads, focussing on the simplest concrete examples: sphere-monopole compactifications in six dimensions. Without gravity most monopoles in non-abelian gauge groups are unstable, decaying into the unique stable monopole in the same topological class. We show that the same is true in Einstein-YM systems, with the new twist that the decay leads to a shrinkage in the size of the extra dimensions and curves the non-compact directions: in D dimensions a Mink{sub D-2} x S{sub 2} geometry supported by an unstable monopole relaxes to AdS{sub D-2} x S{sub 2}, with the endpoint sphere smaller than the initial one. For supergravity the situation is more complicated because the dilaton obstructs such a simple evolution. The endpoint instead acquires a dilaton gradient, thereby breaking some of the spacetime symmetries. For 6D supergravity we argue that it is the 4D symmetries that break, and examine several candidates for the endpoint geometry. By using the trick of dimensional oxidation it is possible to recast the supergravity system as a higher-dimensional Einstein-YM monopole, allowing understanding of this system to guide us to the corresponding endpoint. The result is a Kasner-like geometry conformal to Mink{sub 4} times S{sub 2}, with nontrivial conformal factor and dilaton breaking the maximal 4D symmetry and generating a singularity. Yet the resulting configuration has a lower potential energy than did the initial one, and is perturbatively stable, making it a sensible candidate endpoint for the evolution. (orig.)

The fate of unstable gauge flux compactifications

International Nuclear Information System (INIS)

Burgess, C.P.; Parameswaran, S.L.; Zavala, I.

2008-12-01

Fluxes are widely used to stabilise extra dimensions, but the supporting monopolelike configurations are often unstable, particularly if they arise as gauge flux within a non-abelian gauge sector. We here seek the endpoint geometries to which this instability leads, focussing on the simplest concrete examples: sphere-monopole compactifications in six dimensions. Without gravity most monopoles in non-abelian gauge groups are unstable, decaying into the unique stable monopole in the same topological class. We show that the same is true in Einstein-YM systems, with the new twist that the decay leads to a shrinkage in the size of the extra dimensions and curves the non-compact directions: in D dimensions a Mink D-2 x S 2 geometry supported by an unstable monopole relaxes to AdS D-2 x S 2 , with the endpoint sphere smaller than the initial one. For supergravity the situation is more complicated because the dilaton obstructs such a simple evolution. The endpoint instead acquires a dilaton gradient, thereby breaking some of the spacetime symmetries. For 6D supergravity we argue that it is the 4D symmetries that break, and examine several candidates for the endpoint geometry. By using the trick of dimensional oxidation it is possible to recast the supergravity system as a higher-dimensional Einstein-YM monopole, allowing understanding of this system to guide us to the corresponding endpoint. The result is a Kasner-like geometry conformal to Mink 4 times S 2 , with nontrivial conformal factor and dilaton breaking the maximal 4D symmetry and generating a singularity. Yet the resulting configuration has a lower potential energy than did the initial one, and is perturbatively stable, making it a sensible candidate endpoint for the evolution. (orig.)

Two dimensional unstable scar statistics.

Energy Technology Data Exchange (ETDEWEB)

Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Kotulski, Joseph Daniel; Lee, Kelvin S. H. (ITT Industries/AES Los Angeles, CA)

2006-12-01

This report examines the localization of time harmonic high frequency modal fields in two dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This paper examines the enhancements for these unstable orbits when the opposing mirrors are both convex and concave. In the latter case the construction includes the treatment of interior foci.

Case report: an unstable wide QRS complexes tachycardia after ablation of a poster-septal accessory pathway: What is the mechanism?

Science.gov (United States)

Wang, Huan; Che, Xiaoru

2018-03-01

Differentiation of wide QRS complex tachycardia required repeated electrophysiological stimuli and mapping. However, instability of tachycardia would increase the difficulty in differential diagnosis. In this paper, we reported a wide QRS tachycardia following ablation of an atrioventricular reentrant tachycardia participated by a poster-septal accessory pathway. Limited differentiation strategy was performed because the wide QRS tachycardia was self-limited and with unstable hemodynamics. We analyzed the mechanism of the wide QRS tachycardia by only 4 beats ventricular overpacing. On the basis of the last ventricular pacing, an atypical atrioventricular nodal reentrant tachycardia was confirmed. After slow-pathway modification, the wide QRS tachycardia was eliminated. It was an atypical atrial-ventricular node reentrant tachycardia with right bundle branch block. Reasonable analysis based on electrophysiological electrophysiologic knowledge was the basis of successful diagnosis and treatment.

Characterization of acid-base properties of unstable drugs using a continuous-flow system with UV-vis spectrophotometric detection.

Science.gov (United States)

Argemí, Anna; Saurina, Javier

2007-08-15

In this paper, we propose a continuous-flow system for the study of the acid-base characteristics of unstable drugs. 5-Azacytidine has been selected as a first model of unstable compound, which progressively decomposes in aqueous solutions. Besides, other compounds undergoing hydrolysis and oxidation side reactions have been also analyzed to explore the performance of the method. In comparison with conventional batch titrations, the drug decomposition can be minimized by the continuous renewal of the analyte solution. The composition of the buffer mixture is varied on-line during the process from successive changes in the flow rates of acid and basic stock solutions. As a result, the pH value of the test solution is varied in a controlled manner in the range of 1-13. Multivariate curve resolution based on alternating least squares has been used to extract relevant information concerning the acid-base properties of analytes. Results from the continuous-flow system have been compared with those obtained, using batch spectrophotometric titrations, and in the case of fast degradations, the performance of the proposed procedure has been superior.

Hemodynamic effects of various support modes of continuous flow LVADs on the cardiovascular system: A numerical study

Science.gov (United States)

Song, Zhiming; Gu, Kaiyun; Gao, Bin; Wan, Feng; Chang, Yu; Zeng, Yi

2014-01-01

Background The aim of this study was to determine the hemodynamic effects of various support modes of continuous flow left ventricular assist devices (CF-LVADs) on the cardiovascular system using a numerical cardiovascular system model. Material/Methods Three support modes were selected for controlling the CF-LVAD: constant flow mode, constant speed mode, and constant pressure head mode of CF-LVAD. The CF-LVAD is established between the left ventricular apex and the ascending aorta, and was incorporated into the numerical model. Various parameters were evaluated, including the blood assist index (BAI), the left ventricular external work (LVEW), the energy of blood flow (EBF), pulsatility index (PI), and surplus hemodynamic energy (SHE). Results The results show that the constant flow mode, when compared to the constant speed mode and the constant pressure head mode, increases LVEW by 31% and 14%, and EBF by 21% and 15%, respectively, indicating that this mode achieved the best ventricular unloading among the 3 support modes. As BAI is increased, PI and SHE are gradually decreased, whereas PI of the constant pressure head reaches the maximum value. Conclusions The study demonstrates that the continuous flow control mode of the CF-LVAD may achieve the highest ventricular unloading. In contrast, the constant rotational speed mode permits the optimal blood perfusion. Finally, the constant pressure head strategy, permitting optimal pulsatility, should optimize the vascular function. PMID:24793178

Unstable Resonator Retrofitted Handheld Laser Designator

Science.gov (United States)

1978-06-01

retrofitted with a negative-branch unstable resona- tor laser and hybrid pump cavity in place of the conventional plane-mirror/ porro prism resonator and...directed by prism B to an expanding telescope, shared with the viewing system of the designator. The actual, unfolded resonator length is approxi...was performed based on using a plane- parallel cavity consisting of a 47% reflectivity output coupler, porro - prism reflector, and the same LiNb03

Hemodynamic characterization of chronic bile duct-ligated rats: effect of pentobarbital sodium

International Nuclear Information System (INIS)

Lee, S.S.; Girod, C.; Braillon, A.; Hadengue, A.; Lebrec, D.

1986-01-01

Systemic and splanchnic hemodynamics of the chronic bile duct-ligated rat were characterized by radioactive microspheres. Conscious and pentobarbital sodium-anesthetized, bile duct-ligated and sham-operated rats had cardiac output and regional organ blood flows determined. The conscious bile duct-ligated rat compared with the sham-operated showed a hyperdynamic circulation with an increased cardiac output and portal tributary blood flow. Pentobarbital sodium anesthesia induced marked hemodynamic changes in both sham-operated and bile duct-ligated rats. The latter group was especially sensitive to its effects; thus, comparison of cardiac output and portal tributary blood flow between anesthetized bile duct-ligated and sham-operated rats showed no significant differences. The authors conclude that the rat with cirrhosis due to chronic bile duct ligation is an excellent model for hemodynamic investigations but should be studied in the conscious state, since pentobarbital sodium anesthesia eliminated the hyperdynamic circulation

Natriuretic peptides in unstable coronary artery disease.

Science.gov (United States)

Jernberg, Tomas; James, Stefan; Lindahl, Bertil; Johnston, Nina; Stridsberg, Mats; Venge, Per; Wallentin, Lars

2004-09-01

Patients with unstable coronary artery disease (CAD), i.e., unstable angina or non-ST-elevation myocardial infarction, vary widely in clinical presentation, prognosis and response to treatment. To select appropriate therapy, early risk stratification has become increasingly important. This review focuses on the emerging role of natriuretic peptides in the early assessment of patients with unstable CAD. We conclude that levels of brain natriuretic peptide (BNP) and N-terminal pro-brain natriuretic peptide (NT-proBNP) are strongly associated to mortality and the risk of future congestive heart failure, and carry important prognostic information independent from previously known risk factors in unstable CAD. There are some data indicating that these markers can also be helpful in the selection of appropriate therapy in these patients but further studies are needed. Before a routine use of BNP or NT-proBNP in unstable CAD can be recommended, the cost-effectiveness of adding these new markers to the currently routine markers and their impact on selection of treatment needs further evaluation. Copyright 2004 Elsevier Ltd

One-dimensional unstable eigenfunction and manifold computations in delay differential equations

International Nuclear Information System (INIS)

Green, Kirk; Krauskopf, Bernd; Engelborghs, Koen

2004-01-01

In this paper we present a new numerical technique for computing the unstable eigenfunctions of a saddle periodic orbit in a delay differential equation. This is used to obtain the necessary starting data for an established algorithm for computing one-dimensional (1D) unstable manifolds of an associated saddle fixed point of a suitable Poincare map. To illustrate our method, we investigate an intermittent transition to chaos in a delay system describing a semiconductor laser subject to phase-conjugate feedback

Flights between a neighborhoods of unstable libration points of Sun-Earth system

Science.gov (United States)

Surkova, Valerya; Shmyrov, Vasily

2018-05-01

In this paper we study the problem of constructing impulse flights between neighborhoods of unstable collinear libration points of the Sun-Earth system [1]. Such maneuvering in near-Earth space may prove to be in demand in modern space navigation. For example, such a maneuvering was done by the space vehicle GENESIS. Three test points are chosen for the implementation of the impulse control, in order to move to a neighborhood of the libration point L2. It is shown that the earlier on the exit from the vicinity of the libration point L1 impulse control was realized, the sooner the neighborhood L2 was achieved. Separated from this problem, the problem of optimal control in the neighborhood of L2 was considered and a form of stabilizing control is presented.

Plasma ADAMTS-13 protein is not associated with portal hypertension or hemodynamic changes in patients with cirrhosis

DEFF Research Database (Denmark)

Wiese, Signe; Timm, Annette; Nielsen, Lars B

2016-01-01

BACKGROUND: Activated hepatic stellate cells synthesize the matrix metalloprotease ADAMTS13, which may be involved in the development of liver cirrhosis and portal hypertension. Plasma ADAMTS13 activity has been reported as both increased and decreased in cirrhosis, but ADAMTS13 protein has...... in cirrhosis. However, ADAMTS13 was unrelated to portal hypertension and systemic hemodynamics. In conclusion, ADAMTS13 does not appear to be associated to disease severity or the hemodynamic derangement in patients with cirrhosis....... not previously been examined. AIM: To evaluate ADAMTS13 protein in the hepatic circulation and the relation to disease severity, portal pressure, and systemic hemodynamics in cirrhotic patients. METHODS: Sixty-one cirrhotic patients (Child class: A=22; B=21; C=18) and nine healthy controls underwent a liver vein...

Neuromuscular adjustments of gait associated with unstable conditions

Science.gov (United States)

Ivanenko, Y. P.; d'Avella, A.; Serrao, M.; Ranavolo, A.; Draicchio, F.; Cappellini, G.; Casali, C.; Lacquaniti, F.

2015-01-01

A compact description of coordinated muscle activity is provided by the factorization of electromyographic (EMG) signals. With the use of this approach, it has consistently been shown that multimuscle activity during human locomotion can be accounted for by four to five modules, each one comprised of a basic pattern timed at a different phase of gait cycle and the weighting coefficients of synergistic muscle activations. These modules are flexible, in so far as the timing of patterns and the amplitude of weightings can change as a function of gait speed and mode. Here we consider the adjustments of the locomotor modules related to unstable walking conditions. We compared three different conditions, i.e., locomotion of healthy subjects on slippery ground (SL) and on narrow beam (NB) and of cerebellar ataxic (CA) patients on normal ground. Motor modules were computed from the EMG signals of 12 muscles of the right lower limb using non-negative matrix factorization. The unstable gait of SL, NB, and CA showed significant changes compared with controls in the stride length, stride width, range of angular motion, and trunk oscillations. In most subjects of all three unstable conditions, >70% of the overall variation of EMG waveforms was accounted for by four modules that were characterized by a widening of muscle activity patterns. This suggests that the nervous system adopts the strategy of prolonging the duration of basic muscle activity patterns to cope with unstable conditions resulting from either slippery ground, reduced support surface, or pathology. PMID:26378199

Abnormal hemodynamic response to forepaw stimulation in rat brain after cocaine injection

Science.gov (United States)

Chen, Wei; Park, Kicheon; Choi, Jeonghun; Pan, Yingtian; Du, Congwu

2015-03-01

Simultaneous measurement of hemodynamics is of great importance to evaluate the brain functional changes induced by brain diseases such as drug addiction. Previously, we developed a multimodal-imaging platform (OFI) which combined laser speckle contrast imaging with multi-wavelength imaging to simultaneously characterize the changes in cerebral blood flow (CBF), oxygenated- and deoxygenated- hemoglobin (HbO and HbR) from animal brain. Recently, we upgraded our OFI system that enables detection of hemodynamic changes in response to forepaw electrical stimulation to study potential brain activity changes elicited by cocaine. The improvement includes 1) high sensitivity to detect the cortical response to single forepaw electrical stimulation; 2) high temporal resolution (i.e., 16Hz/channel) to resolve dynamic variations in drug-delivery study; 3) high spatial resolution to separate the stimulation-evoked hemodynamic changes in vascular compartments from those in tissue. The system was validated by imaging the hemodynamic responses to the forepaw-stimulations in the somatosensory cortex of cocaine-treated rats. The stimulations and acquisitions were conducted every 2min over 40min, i.e., from 10min before (baseline) to 30min after cocaine challenge. Our results show that the HbO response decreased first (at ~4min) followed by the decrease of HbR response (at ~6min) after cocaine, and both did not fully recovered for over 30min. Interestingly, while CBF decreased at 4min, it partially recovered at 18min after cocaine administration. The results indicate the heterogeneity of cocaine's effects on vasculature and tissue metabolism, demonstrating the unique capability of optical imaging for brain functional studies.

Echocardiographic Evaluation of Hemodynamics in Neonates and Children

Directory of Open Access Journals (Sweden)

Yogen Singh

2017-09-01

Full Text Available Hemodynamic instability and inadequate cardiac performance are common in critically ill children. The clinical assessment of hemodynamic status is reliant upon physical examination supported by the clinical signs such as heart rate, blood pressure, capillary refill time, and measurement of the urine output and serum lactate. Unfortunately, all of these parameters are surrogate markers of cardiovascular well-being and they provide limited direct information regarding the adequacy of blood flow and tissue perfusion. A bedside point-of-care echocardiography can provide real-time hemodynamic information by assessing cardiac function, loading conditions (preload and afterload and cardiac output. The echocardiography has the ability to provide longitudinal functional assessment in real time, which makes it an ideal tool for monitoring hemodynamic assessment in neonates and children. It is indispensable in the management of patients with shock, pulmonary hypertension, and patent ductus arteriosus. The echocardiography is the gold standard diagnostic tool to assess hemodynamic stability in patients with pericardial effusion, cardiac tamponade, and cardiac abnormalities such as congenital heart defects or valvar disorders. The information from echocardiography can be used to provide targeted treatment in intensive care settings such as need of fluid resuscitation versus inotropic support, choosing appropriate inotrope or vasopressor, and in providing specific interventions such as selective pulmonary vasodilators in pulmonary hypertension. The physiological information gathered from echocardiography may help in making timely, accurate, and appropriate diagnosis and providing specific treatment in sick patients. There is no surprise that use of bedside point-of-care echocardiography is rapidly gaining interest among neonatologists and intensivists, and it is now being used in clinical decision making for patients with hemodynamic instability. Like any

Diagnosis of Unstable Angina Pectoris Has Declined Markedly with the Advent of More Sensitive Troponin Assays

DEFF Research Database (Denmark)

D'Souza, Maria; Sarkisian, Laura; Saaby, Lotte

2015-01-01

]) was established in cases of a rise and/or fall of cardiac troponin I together with cardiac ischemic features. Patients with unstable chest discomfort and cardiac troponin I values below the decision limit of myocardial infarction were diagnosed as having unstable angina pectoris. The definition of acute coronary...... syndrome included unstable angina pectoris, NSTEMI, and STEMI. Mortality data were obtained from the Danish Civil Personal Registration System. RESULTS: Of 3762 consecutive patients, 516 had acute coronary syndrome. Unstable angina pectoris was present in 7%, NSTEMI in 67%, and STEMI in 26%. The NSTEMI...... patients were older, more frequently women, and had more comorbidities than patients with unstable angina pectoris and STEMI. At median follow-up of 3.2 years 195 patients had died: 14% of unstable angina pectoris, 45% of NSTEMI, and 25% of STEMI patients. Age-adjusted log-rank statistics revealed...

Hemodynamic disturbances in cerebral ischemia; Correlation between positron emission tomographic and angiographic findings

Energy Technology Data Exchange (ETDEWEB)

Tenjin, Hiroshi; Ueda, Satoshi; Mizukawa, Norihiko; Imahori, Yoshio; Hino, Akihiko; Ohmori, Yoshio [Kyoto Prefectural Univ. of Medicine (Japan); Nakahashi, Hisamitsu

1993-04-01

Proper treatment of ischemic stroke requires better understanding of cerebral hemodynamic changes. The hemodynamic changes associated with ischemia were measured using positron emission tomography and related to angiographic findings in the subacute and chronic stages of 17 ischemia patients who showed symptoms of main trunk stenosis of the internal carotid artery system. The hemodynamic factors, cerebral blood flow, cerebral blood volume, cerebral metabolic rate for oxygen, oxygen extraction fraction, and flow/volume ratio, were measured in regions of interest determined from the angiographic stenosis (over 50%) and compared in each stage. The cerebral blood flow and flow/volume ratio in the territory downstream of the main trunk stenosis and cerebral metabolic rate for oxygen in the whole cortex were decreased in the subacute stage. In the chronic stage, cerebral blood flow and flow/volume ratio decreased mainly in borderzone areas. (author).

Generating Unstable Resonances for Extraction Schemes Based on Transverse Splitting

CERN Document Server

Giovannozzi, M; Turchetti, G

2009-01-01

A few years ago, a novel multi-turn extraction scheme was proposed, based on particle trapping inside stable resonances. Numerical simulations and experimental tests have confirmed the feasibility of such a scheme for low order resonances. While the third-order resonance is generically unstable and those higher than fourth-order are generically stable, the fourth-order resonance can be either stable or unstable depending on the specifics of the system under consideration. By means of the Normal Form a general approach to control the stability of the fourth-order resonance has been derived. This approach is based on the control of the amplitude detuning and the general form for a lattice with an arbitrary number of sextupole and octupole families is derived in this paper. Numerical simulations have confirmed the analytical results and have shown that, when crossing the unstable fourth-order resonance, the region around the centre of the phase space is depleted and particles are trapped in only the four stable ...

Measurements of coherent hemodynamics to enrich the physiological information provided by near-infrared spectroscopy (NIRS) and functional MRI

Science.gov (United States)

Sassaroli, Angelo; Tgavalekos, Kristen; Pham, Thao; Krishnamurthy, Nishanth; Fantini, Sergio

2018-02-01

Hemodynamic-based neuroimaging techniques such as functional magnetic resonance imaging (fMRI) and near-infrared spectroscopy (NIRS) sense hemoglobin concentration in cerebral tissue. The local concentration of hemoglobin, which is differentiated into oxy- and deoxy-hemoglobin by NIRS, features spontaneous oscillations over time scales of 10-100 s in response to a number of local and systemic physiological processes. If one of such processes becomes the dominant source of cerebral hemodynamics, there is a high coherence between this process and the associated hemodynamics. In this work, we report a method to identify such conditions of coherent hemodynamics, which may be exploited to study and quantify microvasculature and microcirculation properties. We discuss how a critical value of significant coherence may depend on the specific data collection scheme (for example, the total acquisition time) and the nature of the hemodynamic data (in particular, oxy- and deoxy-hemoglobin concentrations measured with NIRS show an intrinsic level of correlation that must be taken into account). A frequency-resolved study of coherent hemodynamics is the basis for the new technique of coherent hemodynamics spectroscopy (CHS), which aims to provide measures of cerebral blood flow and cerebral autoregulation. While these concepts apply in principle to both fMRI and NIRS data, in this article we focus on NIRS data.

Availability of a remote online hemodynamic monitoring system during treatment in a private dental office for medically high-risk patients

Directory of Open Access Journals (Sweden)

Shinya Yamazaki

2008-09-01

Full Text Available Shinya Yamazaki, Hiroyoshi Kawaai, Shigeo Sasaki, Kazuhiro Shimamura, Hiroshi Segawa, Takahiro SaitoSpecial Care Department in Dentistry, Ohu University Dental Hospital, Koriyama city, Fukushima prefecture, JapanAbstract: The importance of systemic management to prevent accidents is increasing in dentistry because co-morbid illnesses in an aging society and invasive surgical procedures are increasing. In this prefecture, a new medical system called the remote online hemodynamic monitoring system (ROHMs was started in 2001. Eight private dental offices participated in this trial. When dental practitioners feel the risk of a dental procedure, they can contact via ROHMs to this hospital. Then, the hemodynamic data (blood pressure, heart rate, ECG, SpO2, and RPP of the patient in the clinic can be transmitted here via the internet, and the images and the voice can be transmitted as well. The availability of this system was assessed in 66 patients (98 cases. The most frequent complications were hypertension, heart disease, and diabetes mellitus. Systemic management included monitoring during the dental procedure (71.4%, checking vital signs after an interview (15.3%, and monitoring under sedation (13.3%. There were 35.7% of all cases where an unscheduled procedure was necessary for the systemic management. Based on a questionnaire, the majority of the patients felt relieved and safe. This system creates a situation where a specialist is almost present during the procedure. This system will provide significant assistance for future medical cooperation for risk management.Keywords: online, high-risk patient, dental treatment, medical cooperation, medical accident, risk management

[Correlation between the width of lingual vein and the changes of hemodynamics of portal system in patients with primary liver cancer].

Science.gov (United States)

Yue, Xiao-Qiang; Gao, Jing-Dong; Zhai, Xiao-Feng; Liu, Qing; Jiang, Dong; Ling, Chang-Quan

2006-09-01

To explore the correlation between the width of lingual varix and changes of hemodynamics of portal system in patients with primary liver cancer so as to supply the data for the forecast of portal hypertension by observing lingual varix. The diameter of lingual vein (Dlv) was measured by vernier caliper as dependent variable, and the diameters and indexes of hemodynamics of portal vessels were measured by Doppler as independent variables, then a multipe stepwise analysis was performed. The diameters of portal vein (Dpv) and splenic vein (Dsv) entered the formula Dlv (mm) = 0.185 + 0.311 Dsv (mm) + 0.236 Dpv (mm) when the entry and removal values were alpha(in)=0.10 and alpha(out)=0.15, respectively. The width of lingual vein is closely correlated with the diameters of portal vein and splenic vein in patients with primary liver cancer.

A Novel Stretch Sensor to Measure Venous Hemodynamics

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Syrpailyne Wankhar

2018-07-01

Full Text Available Chronic venous insufficiency is a debilitating condition causing varicose veins and venous ulcers. The pathophysiology includes reflux and venous obstruction. The diagnosis is often made by clinical examination and confirmed by Venous Doppler studies. Plethysmography helps to quantitatively examine the reflux and diagnose the burden of deep venous pathology to better understand venous hemodynamics, which is not elicited by venous duplex examination alone. However, most of these tests are qualitative, expensive, and not easily available. In this paper, we demonstrate the potential use of a novel stretch sensor in the assessment of venous hemodynamics during different maneuvers by measuring the change in calf circumference. We designed the stretch sensor by using semiconductor strain gauges pasted onto a small metal bar to form a load cell. The elastic and Velcro material attached to the load cell form a belt. It converts the change in limb circumference to a proportional tension (force of distension when placed around the calf muscle. We recorded the change in limb circumference from arrays of stretch sensors by using an in-house data acquisition system. We calculated the venous volume (VV, venous filling index (VFI, ejection fraction (EF and residual venous volume (RVV on two normal subjects and on two patients to assess venous hemodynamics. The values (VV > 60 ml, VFI 60%, RVV 2ml/s, EF 35% in patients were comparable to those reported in the literature.

Cerebral hemodynamics and systemic endothelial function are already impaired in well-controlled type 2 diabetic patients, with short-term disease.

Directory of Open Access Journals (Sweden)

Paola Palazzo

Full Text Available Impaired cerebral vasomotor reactivity (VMR and flow-mediated dilation (FMD were found in selected subgroups of type 2 diabetes mellitus (T2DM patients with long-term disease. Our study aimed to evaluate cerebral hemodynamics, systemic endothelial function and sympatho-vagal balance in a selected population of well-controlled T2DM patients with short-term disease and without cardiac autonomic neuropathy (CAN.Twenty-six T2DM patients with short-term (4.40±4.80 years and well-controlled (HbA1C = 6.71±1.29% disease, without any complications, treated with diet and/or metformin, were consecutively recruited. Eighteen controls, comparable by sex and age, were enrolled also.FMD and shear rate FMD were found to be reduced in T2DM subjects with short-term disease (8.5% SD 3.5 and 2.5 SD 1.3, respectively compared to controls (15.4% SD 4.1 and 3.5 SD 1.4; p.05.In well-controlled T2DM patients with short-term disease cerebral hemodynamics and systemic endothelial function are altered while autonomic balance appeared to be preserved.

Hemodynamics Modeling and Simulation of Anterior Communicating Artery Aneurysms

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Jianjun Li

2014-07-01

Full Text Available It is a general agreement that hemodynamics plays very important role in the initiation, growth, and rupture of cerebral aneurysms and hemodynamics in the anterior communicating artery aneurysms is considered the most complex in all cerebral aneurysms and it is difficult to find some reasonable relationship between the hemodynamics parameters and the rupture risk. In this paper, the 3D geometries of four anterior communicating artery aneurysms were generated from the CTA data and the computational models with bilateral feeding arteries for the four aneurysms were constructed. The blood flow was simulated by computational fluid dynamics software and the hemodynamics parameters such as velocity, wall shear stress, and oscillatory shear index were calculated. The following results were observed: one of the four models only needs the left feeding artery; the max normalized wall shear stress locates at the aneurysmal neck of the largest aneurysm; the max oscillatory shear index locates at the aneurysmal sac of the largest aneurysm. The conclusion was drawn that the anterior communicating artery aneurysm has higher rupture risk from the hemodynamics viewpoint if the max wall shear stress locates at the neck and the max oscillatory shear index locates at the dome.

Intracranial Vascular Disease Evaluation With Combined Vessel Wall Imaging And Patient Specific Hemodynamics

Science.gov (United States)

Samson, Kurt; Mossa-Basha, Mahmud; Yuan, Chun; Canton, Maria De Gador; Aliseda, Alberto

2017-11-01

Intracranial vascular pathologies are evaluated with angiography, conventional digital subtraction angiography or non-invasive (MRI, CT). Current techniques present limitations on the resolution with which the vessel wall characteristics can be measured, presenting a major challenge to differential diagnostic of cerebral vasculopathies. A new combined approach is presented that incorporates patient-specific image-based CFD models with intracranial vessel-wall MRI (VWMRI). Comparisons of the VWMRI measurements, evaluated for the presence of wall enhancement and thin-walled regions, against CFD metrics such as wall shear stress (WSS), and oscillatory shear index (OSI) are used to understand how the new imaging technique developed can predict the influence of hemodynamics on the deterioration of the aneurysmal wall, leading to rupture. Additionally, histology of each resected aneurysm, evaluated for inflammatory infiltration and wall thickness features, is used to validate the analysis from VWMRI and CFD. This data presents a solid foundation on which to build a new framework for combined VWMRI-CFD to predict unstable wall changes in unruptured intracranial aneurysms, and support clinical monitoring and intervention decisions.

Quantum electrodynamics with unstable vacuum

Energy Technology Data Exchange (ETDEWEB)

Fradkin, E.S. (P.N. Lebedev Physical Inst., USSR Academy of Sciences, Moscow (USSR)); Gitman, D.M. (Moscow Inst. of Radio Engineering Electronics and Automation (USSR)); Shvartsman, Sh.M. (Tomsk State Pedagogical Inst. (USSR))

1991-01-01

Intense external fields destabilize vacuum inducing the creation of particle pairs. In this book the formalism of quantum electrodynamics (QED), using a special perturbation theory with matrix propagators, is systematically analyzed for such systems. The developed approach is, however, general for any quantum field with unstable vacuum. The authors propose solutions for real pair-creating fields. They discuss the general form for the causal function and many other Green's functions, as well as methods for finding them. Analogies to the optical theorem and rules for computing total probabilities are given, as are solutions for non-Abelian theories. (orig.).

Numerical reproduction of hemodynamics change by acupuncture on Taichong (LR-3 based on the lumped-parameter approximation model of the systemic arteries

Directory of Open Access Journals (Sweden)

Atsushi Shirai

2015-09-01

Conclusion: The present model has a potential to emulate hemodynamic change by acupuncture therapy by incorporating physiological correlation of stimulation of an acupoint and regulation of parameters that affect the hemodynamics.

Electromagnetic Radiation Originating from Unstable Electron Oscillations

DEFF Research Database (Denmark)

Juul Rasmussen, Jens; Pécseli, Hans

1975-01-01

Electromagnetic oscillations in the range 300 – 700 MHz were observed from an unmagnetized argon discharge with an unstable electron velocity distribution function.......Electromagnetic oscillations in the range 300 – 700 MHz were observed from an unmagnetized argon discharge with an unstable electron velocity distribution function....

Pole mass, width, and propagators of unstable fermions

International Nuclear Information System (INIS)

Kniehl, B.A.; Sirlin, A.

2008-01-01

The concepts of pole mass and width are extended to unstable fermions in the general framework of parity-nonconserving gauge theories, such as the Standard Model. In contrast with the conventional on-shell definitions, these concepts are gauge independent and avoid severe unphysical singularities, properties of great importance since most fundamental fermions in nature are unstable particles. General expressions for the unrenormalized and renormalized dressed propagators of unstable fermions and their field-renormalization constants are presented. (orig.)

Imaging unstable plaque

International Nuclear Information System (INIS)

SRIRANJAN, Rouchelle S.; TARKIN, Jason M.; RUDD, James H.; EVANS, Nicholas R.; CHOWDHURY, Mohammed M.

2016-01-01

Recent advances in imaging technology have enabled us to utilise a range of diagnostic approaches to better characterise high-risk atherosclerotic plaque. The aim of this article is to review current and emerging techniques used to detect and quantify unstable plaque in the context of large and small arterial systems and will focus on both invasive and non-invasive imaging techniques. While the diagnosis of clinically relevant atherosclerosis still relies heavily on anatomical assessment of arterial luminal stenosis, evolving multimodal cross-sectional imaging techniques that encompass novel molecular probes can provide added information with regard to plaque composition and overall disease burden. Novel molecular probes currently being developed to track precursors of plaque rupture such as inflammation, micro-calcification, hypoxia and neoangiogenesis are likely to have translational applications beyond diagnostics and have the potential to play a part in quantifying early responses to therapeutic interventions and more accurate cardiovascular risk stratification.

Correlation between electrical and hemodynamic responses during visual stimulation with graded contrasts

Science.gov (United States)

Si, Juanning; Zhang, Xin; Li, Yuejun; Zhang, Yujin; Zuo, Nianming; Jiang, Tianzi

2016-09-01

Brain functional activity involves complex cellular, metabolic, and vascular chain reactions, making it difficult to comprehend. Electroencephalography (EEG) and functional near infrared spectroscopy (fNIRS) have been combined into a multimodal neuroimaging method that captures both electrophysiological and hemodynamic information to explore the spatiotemporal characteristics of brain activity. Because of the significance of visually evoked functional activity in clinical applications, numerous studies have explored the amplitude of the visual evoked potential (VEP) to clarify its relationship with the hemodynamic response. However, relatively few studies have investigated the influence of latency, which has been frequently used to diagnose visual diseases, on the hemodynamic response. Moreover, because the latency and the amplitude of VEPs have different roles in coding visual information, investigating the relationship between latency and the hemodynamic response should be helpful. In this study, checkerboard reversal tasks with graded contrasts were used to evoke visual functional activity. Both EEG and fNIRS were employed to investigate the relationship between neuronal electrophysiological activities and the hemodynamic responses. The VEP amplitudes were linearly correlated with the hemodynamic response, but the VEP latency showed a negative linear correlation with the hemodynamic response.

Unstable Titan-generated Rayleigh-Taylor Lakes Impact Ice

Science.gov (United States)

Umurhan, O. M.; Korycansky, D. G.; Zahnle, K. J.

2014-12-01

The evolution of surface morphology on Titan, Triton, and other worlds is strongly influenced by the interplay of various fluid dynamical processes. Specifically, overturning instabilities can easily arise due to the special circumstances of landform evolution that probably occurred on these worlds. On Titan, large impacts that formed basins like Menrva crater (and possibly Hotei Regio) would have generated impact-melt ice lakes unstably arranged over less dense ice. Cantaloupe terrains, for example as seen on Triton, may be the result of condensation of volatiles (methane, nitrogen) leading to unstably stratified layers of different compositions and densities. In each of these cases, Rayleigh-Taylor instabilities leading to large scale diapirism may be at play. In addition to the dynamics of these instabilities, other physical effects (e.g. heat diffusion, freezing/melting, porosity, temperature dependent viscosity) likely play an important role in the evolution of these features. In this ongoing study, we examine the properties of unstably stratified fluids in which the lower less-dense ice has a temperature dependent viscosity. Surprisingly, we find that there exists an optimal disturbance length scale corresponding to the fastest growth of the Rayleigh-Taylor instability. For unstably stratified layers of water (low viscosity heavy liquid lying above an ice whose viscosity increases with depth) the fastest growing mode corresponds to 40-60 km scales with overturn times of approximately 100 days. We present a detailed numerical stability analysis in a corresponding Boussinessq model (in the creeping flow limit) incorporating thermal conduction and latent heat release and we examine the stability properties surveying a variety of parameters. We have also developed a two-dimensional numerical code (a hybrid spectral/compact-differencing scheme) to model the evolution of such systems for which we shall present preliminary numerical results depicting the outcome of

Generating unstable resonances for extraction schemes based on transverse splitting

Directory of Open Access Journals (Sweden)

M. Giovannozzi

2009-02-01

Full Text Available A few years ago, a novel multiturn extraction scheme was proposed, based on particle trapping inside stable resonances. Numerical simulations and experimental tests have confirmed the feasibility of such a scheme for low order resonances. While the third-order resonance is generically unstable and those higher than fourth order are generically stable, the fourth-order resonance can be either stable or unstable depending on the specifics of the system under consideration. By means of the normal form, a general approach to control the stability of the fourth-order resonance has been derived. This approach is based on the control of the amplitude detuning and the general form for a lattice with an arbitrary number of sextupole and octupole families is derived in this paper. Numerical simulations have confirmed the analytical results and have shown that, when crossing the unstable fourth-order resonance, the region around the center of the phase space is depleted and particles are trapped in only the four stable islands. A four-turn extraction could be designed using this technique.

Reliability of unstable periodic orbit based control strategies in biological systems

Energy Technology Data Exchange (ETDEWEB)

Mishra, Nagender; Singh, Harinder P. [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Hasse, Maria [Institut für Höchstleistungsrechnen, Universität Stuttgart, D-70569 Stuttgart (Germany); Biswal, B. [Cluster Innovation Center, University of Delhi, Delhi 110007 (India); Sri Venkateswara College, University of Delhi, Delhi 110021 (India)

2015-04-15

Presence of recurrent and statistically significant unstable periodic orbits (UPOs) in time series obtained from biological systems is now routinely used as evidence for low dimensional chaos. Extracting accurate dynamical information from the detected UPO trajectories is vital for successful control strategies that either aim to stabilize the system near the fixed point or steer the system away from the periodic orbits. A hybrid UPO detection method from return maps that combines topological recurrence criterion, matrix fit algorithm, and stringent criterion for fixed point location gives accurate and statistically significant UPOs even in the presence of significant noise. Geometry of the return map, frequency of UPOs visiting the same trajectory, length of the data set, strength of the noise, and degree of nonstationarity affect the efficacy of the proposed method. Results suggest that establishing determinism from unambiguous UPO detection is often possible in short data sets with significant noise, but derived dynamical properties are rarely accurate and adequate for controlling the dynamics around these UPOs. A repeat chaos control experiment on epileptic hippocampal slices through more stringent control strategy and adaptive UPO tracking is reinterpreted in this context through simulation of similar control experiments on an analogous but stochastic computer model of epileptic brain slices. Reproduction of equivalent results suggests that far more stringent criteria are needed for linking apparent success of control in such experiments with possible determinism in the underlying dynamics.

Reliability of unstable periodic orbit based control strategies in biological systems

International Nuclear Information System (INIS)

Mishra, Nagender; Singh, Harinder P.; Hasse, Maria; Biswal, B.

2015-01-01

Presence of recurrent and statistically significant unstable periodic orbits (UPOs) in time series obtained from biological systems is now routinely used as evidence for low dimensional chaos. Extracting accurate dynamical information from the detected UPO trajectories is vital for successful control strategies that either aim to stabilize the system near the fixed point or steer the system away from the periodic orbits. A hybrid UPO detection method from return maps that combines topological recurrence criterion, matrix fit algorithm, and stringent criterion for fixed point location gives accurate and statistically significant UPOs even in the presence of significant noise. Geometry of the return map, frequency of UPOs visiting the same trajectory, length of the data set, strength of the noise, and degree of nonstationarity affect the efficacy of the proposed method. Results suggest that establishing determinism from unambiguous UPO detection is often possible in short data sets with significant noise, but derived dynamical properties are rarely accurate and adequate for controlling the dynamics around these UPOs. A repeat chaos control experiment on epileptic hippocampal slices through more stringent control strategy and adaptive UPO tracking is reinterpreted in this context through simulation of similar control experiments on an analogous but stochastic computer model of epileptic brain slices. Reproduction of equivalent results suggests that far more stringent criteria are needed for linking apparent success of control in such experiments with possible determinism in the underlying dynamics

Immunologic, hemodynamic, and adrenal incompetence in cirrhosis

DEFF Research Database (Denmark)

Risør, Louise Madeleine; Bendtsen, Flemming; Møller, Søren

2015-01-01

dysfunction, but is not responsive to volume expansion. Recent research indicates that development of hepatic nephropathy represents a continuous spectrum of functional and structural dysfunction and may be precipitated by the inherent immunologic, adrenal, and hemodynamic incompetence in cirrhosis. New...... research explores several new markers of renal dysfunction that may replace serum creatinine in the future and give new insight on the hepatic nephropathy. Our understanding of the pathophysiological mechanisms causing the immunologic, adrenal, and hemodynamic incompetence, and the impact on renal...

Obesity and renal hemodynamics

NARCIS (Netherlands)

Bosma, R. J.; Krikken, J. A.; van der Heide, J. J. Homan; de Jong, P. E.; Navis, G. J.

2006-01-01

Obesity is a risk factor for renal damage in native kidney disease and in renal transplant recipients. Obesity is associated with several renal risk factors such as hypertension and diabetes that may convey renal risk, but obesity is also associated with an unfavorable renal hemodynamic profile

Results of operative fixation of unstable ankle fractures in geriatric patients.

Science.gov (United States)

Pagliaro, A J; Michelson, J D; Mizel, M S

2001-05-01

It is widely accepted that operative fixation of unstable ankle fractures yields predictably good outcomes in the general population. The current literature, however reports less acceptable results in the geriatric population age 65 years and older. The current study analyzes the outcome of the surgical treatment of unstable ankle fractures in patients at least 65 years old. Twenty three patient over 65 years old were surgically treated after sustaining 21 (91%) closed and 2 (9%) open grade II unstable ankle fractures. Fractures were classified according to the Danis-Weber and Lauge-Hansen schemes. Fracture type was predominantly Weber B (21/23, 91%), or supination external rotation stage IV (21/23, 91%). Fracture union rate was 100%. There were three significant complications including a lateral wound dehiscence with delayed fibular union in an open fracture dislocation, and two below knee amputations, neither of which was directly related to the fracture treatment. There were three minor complications; one superficial wound infection and two cases of prolonged incision drainage, all of which resolved without further surgical intervention. Complications were associated with open fractures and preexisting systemic disease. These results indicate that open reduction and internal fixation of unstable ankle fractures in geriatric patients is an efficacious treatment regime that with results that are comparable to the general population.

Restrictions in the realisation of multipass unstable resonators

International Nuclear Information System (INIS)

Strakhov, S Yu

2009-01-01

Main restrictions in the realisation of multipass unstable resonators caused by intracavity losses and large-scale aberrations are considered. The influence of intracavity losses on the laser radiation power and divergence is analysed based on the numerical simulation of an unstable resonator. The efficiency criterion for the unstable multipass resonator is proposed, which is proportional to the radiation brightness and takes into account the influence of the misalignment, thermal deformation and the main parameters of the active medium and resonator on the parameters of laser radiation. (resonators)

Percutaneous pedicle screw for unstable spine fractures in polytraumatized patients: A report of two cases

Directory of Open Access Journals (Sweden)

Boon Beng Tan

2012-01-01

Full Text Available Unstable spine fractures commonly occur in the setting of a polytraumatized patient. The aim of management is to balance the need for early operative stabilization and prevent additional trauma due to the surgery. Recent published literature has demonstrated the benefits of early stabilization of an unstable spine fracture particularly in patients with higher injury severity score (ISS. We report two cases of polytrauma with unstable spine fractures stabilized with a minimally invasive percutaneous pedicle screw instrumentation system as a form of damage control surgery. The patients had good recovery from the polytrauma injuries. These two cases illustrate the role of minimally invasive stabilization, its limitations and technical pitfalls in the management of unstable spine fractures in the polytrauma setting as a form of damage control surgery.

Hemodynamics in Korean Hemorrhagic Fever

International Nuclear Information System (INIS)

Han, Ji Young; Lee, Jung Sang; Koh, Chang Soon; Lee, Mun Ho

1974-01-01

The author in an attempt to evaluate hemodynamic changes in the clinical stages of Korean hemorrhagic fever measured plasma volume, cardiac output and effective renal plasma flow utilizing radioisoto as during various phases of the disease. Cardiac output was measured by radiocardiography with external monitoring method using RIHSA. Effective renal plasma flow was obtained from blood clearance curve drawn by external monitoring after radiohippuran injection according to the method described by Razzak et al. The study was carried out in thirty-eight cases of Korean hemorrhagic fever and the following conclusions were obtained. 1) Plasma volume was increased in the patients during the oliguric and hypertensive-diuretic phases, while it was normal in the patients during the normotensive-diuretic phase. 2) Cardiac index was increased in the patients during the oliguric phase and was slightly increased in the patients at the hypertensive diuretic phase. It was normal in the other phases. 3) Total peripheral resistance was increased in the hypertensive patients during diuretic phase, while it was normal in the rest of phases. 4) Effective renal plasma flow was significantly reduced in the patients during the oliguric and diuretic phases as well as at one month after the oliguric onset. There was no significant difference between the oliguric and the early diuretic phases. Renal plasma flow in the group of patients at one month after the oliguric onset was about 45% of the normal, however, it returned to normal level at six months after the onset. 5) Clinical syndrome of relative hypervolemia was observed in some patients during the oliguric phase or hypertensive diuretic phase. Characteristic hemodynamic findings were high cardiac output and normal to relatively increased peripheral resistance these cases. Relatively increased circulating blood volumes due to decreased effective vascular space was suggested for the mechanism of relative hypervolemia. 6) Cardiac

Unstable slope management program.

Science.gov (United States)

2009-08-01

This Rapid Response Project gathered information on existing unstable slope management programs, with a : focus on asset management practices in the United States and overseas. On the basis of this study, the research : team summarized and recommende...

Automatd assessment of the state of central hemodynamics using a radiocardioanalyser RCA 3-01

International Nuclear Information System (INIS)

Sivachenko, T.P.; Zozulya, A.A.; Sribnaya, A.F.; Ratmanskij, A.Yu.; Tishchenko, F.M.; Kurenya, A.G.; Krupka, I.N.; Kulagin, S.N.; Protsenko, A.S.

1987-01-01

The authors presented the results of a clinical use of a new radiocardioanalyzer RCA 3-01 (manufactured in the USSR) providing for automated measurements and computations of indices of the central hemodynamics during studies using a method of dilution of radioactive nuclides. The main technical potentialities of the device designed on the basis of microprocessor technology, were described. The authors also provided the results of automated computation of the circulating blood volume and the main hemodynamic indices in a group of patients. Values of the hemodynamic indices were shown to correspond to actual ones and comparable to control ones and clinical evidence. The comparison of automated processing with a manual method of calculation indicated a significant coincidence of index values. The clinical use of the radiocardioanalyzer RGA 3-01 for automated assessment of the indices of the cardiovascular system was shown to hold promise among various groups of patients

Unstable oscillators based hyperchaotic circuit

DEFF Research Database (Denmark)

Murali, K.; Tamasevicius, A.; G. Mykolaitis, A.

1999-01-01

A simple 4th order hyperchaotic circuit with unstable oscillators is described. The circuit contains two negative impedance converters, two inductors, two capacitors, a linear resistor and a diode. The Lyapunov exponents are presented to confirm hyperchaotic nature of the oscillations in the circ...... in the circuit. The performance of the circuit is investigated by means of numerical integration of appropriate differential equations, PSPICE simulations, and hardware experiment.......A simple 4th order hyperchaotic circuit with unstable oscillators is described. The circuit contains two negative impedance converters, two inductors, two capacitors, a linear resistor and a diode. The Lyapunov exponents are presented to confirm hyperchaotic nature of the oscillations...

Advanced hemodynamic monitoring in intensive care medicine : A German web-based survey study.

Science.gov (United States)

Saugel, B; Reese, P C; Wagner, J Y; Buerke, M; Huber, W; Kluge, S; Prondzinsky, R

2018-04-01

Advanced hemodynamic monitoring is recommended in patients with complex circulatory shock. To evaluate the current attitudes and beliefs among German intensivists, regarding advanced hemodynamic monitoring, the actual hemodynamic management in clinical practice, and the barriers to using it. Web-based survey among members of the German Society of Medical Intensive Care and Emergency Medicine. Of 284 respondents, 249 (87%) agreed that further hemodynamic assessment is needed to determine the type of circulatory shock if no clear clinical diagnosis can be made. In all, 281 (99%) agreed that echocardiography is helpful for this purpose (transpulmonary thermodilution: 225 [79%]; pulmonary artery catheterization: 126 [45%]). More than 70% of respondents agreed that blood flow variables (cardiac output, stroke volume) should be measured in patients with hemodynamic instability. The parameters most respondents agreed should be assessed in a patient with hemodynamic instability were mean arterial pressure, cardiac output, and serum lactate. Echocardiography is available in 99% of ICUs (transpulmonary thermodilution: 91%; pulmonary artery catheter: 63%). The respondents stated that, in clinical practice, invasive arterial pressure measurements and serum lactate measurements are performed in more than 90% of patients with hemodynamic instability (cardiac output monitoring in about 50%; transpulmonary thermodilution in about 40%). The respondents did not feel strong barriers to the use of advanced hemodynamic monitoring in clinical practice. This survey study shows that German intensivists deem advanced hemodynamic assessment necessary for the differential diagnosis of circulatory shock and to guide therapy with fluids, vasopressors, and inotropes in ICU patients.

Hemodynamic response during aneurysm clipping surgery among experienced neurosurgeons.

Science.gov (United States)

Bunevicius, Adomas; Bilskiene, Diana; Macas, Andrius; Tamasauskas, Arimantas

2016-02-01

Neurosurgery is a challenging field associated with high levels of mental stress. The goal of this study was to investigate the hemodynamic response of experienced neurosurgeons during aneurysm clipping surgery and to evaluate whether neurosurgeons' hemodynamic responses are associated with patients' clinical statuses. Four vascular neurosurgeons (all male; mean age 51 ± 10 years; post-residency experience ≥7 years) were studied during 42 aneurysm clipping procedures. Blood pressure (BP) and heart rate (HR) were assessed at rest and during seven phases of surgery: before the skin incision, after craniotomy, after dural opening, after aneurysm neck dissection, after aneurysm clipping, after dural closure and after skin closure. HR and BP were significantly greater during surgery relative to the rest situation (p ≤ 0.03). There was a statistically significant increase in neurosurgeons' HR (F [6, 41] = 10.88, p neurosurgeon experience, the difference in BP as a function of aneurysm rupture was not significant (p > 0.08). Aneurysm location, intraoperative aneurysm rupture, admission WFNS score, admission Glasgow Coma Scale scores and Fisher grade were not associated with neurosurgeons' intraoperative HR and BP (all p > 0.07). Aneurysm clipping surgery is associated with significant hemodynamic system activation among experienced neurosurgeons. The greatest HR and BP were after aneurysm neck dissection and clipping. Aneurysm location and patient clinical status were not associated with intraoperative changes of neurosurgeons' HR and BP.

Dynamic cerebral autoregulation measured with coherent hemodynamics spectroscopy (CHS)

Science.gov (United States)

Kainerstorfer, Jana M.; Sassaroli, Angelo; Tgavalekos, Kristen T.; Fantini, Sergio

2015-03-01

Coherent Hemodynamics Spectroscopy (CHS) is a novel technique for non-invasive measurements of local microcirculation quantities such as the capillary blood transit times and dynamic autoregulation. The basis of CHS is to measure, for instance with near-infrared spectroscopy (NIRS), peripheral coherent hemodynamic changes that are induced by controlled perturbations in the systemic mean arterial pressure (MAP). In this study, the MAP perturbation was induced by the fast release of two pneumatic cuffs placed around the subject's thighs after they were kept inflated (at 200 mmHg) for two minutes. The resulting transient changes in cerebral oxy- (O) and deoxy- (D) hemoglobin concentrations measured with NIRS on the prefrontal cortex are then described by a novel hemodynamic model, from which quantifiable parameters such as the capillary blood transit time and a cutoff frequency for cerebral autoregulation are obtained. We present results on eleven healthy volunteers in a protocol involving measurements during normal breathing and during hyperventilation, which is known to cause a hypocapnia-induced increase in cerebral autoregulation. The measured capillary transit time was unaffected by hyperventilation (normal breathing: 1.1±0.1 s; hyperventilation: 1.1±0.1 s), whereas the cutoff frequency of autoregulation, which increases for higher autoregulation efficiency, was indeed found to be significantly greater during hyperventilation (normal breathing: 0.017±0.002 Hz; hyperventilation: 0.034±0.005 Hz). These results provide a validation of local cerebral autoregulation measurements with the new technique of CHS.

Unstable drift eigenmode in slab geometry

International Nuclear Information System (INIS)

Tsotsonis, S.; Hirose, A.

1986-01-01

The unstable Pearlstein-Berk mode of drift waves in plane, sheared slab geometry has later been shown to be stable when electron Landau resonance is rigorously treated. Based on the variational method previously developed the authors have found that in addition to the absolutely stable Pearlstein-Berk mode, there exists an absolutely unstable eigenfunction characterized by ω ≤ ω/sub chemical bonde/, and weak ''radial'' dependence. Also, the growth rate, only weakly depends on the magnetic shear and ion/electron temperature ratio

Concurrent OCT imaging of stimulus evoked retinal neural activation and hemodynamic responses

Science.gov (United States)

Son, Taeyoon; Wang, Benquan; Lu, Yiming; Chen, Yanjun; Cao, Dingcai; Yao, Xincheng

2017-02-01

It is well established that major retinal diseases involve distortions of the retinal neural physiology and blood vascular structures. However, the details of distortions in retinal neurovascular coupling associated with major eye diseases are not well understood. In this study, a multi-modal optical coherence tomography (OCT) imaging system was developed to enable concurrent imaging of retinal neural activity and vascular hemodynamics. Flicker light stimulation was applied to mouse retinas to evoke retinal neural responses and hemodynamic changes. The OCT images were acquired continuously during the pre-stimulation, light-stimulation, and post-stimulation phases. Stimulus-evoked intrinsic optical signals (IOSs) and hemodynamic changes were observed over time in blood-free and blood regions, respectively. Rapid IOSs change occurred almost immediately after stimulation. Both positive and negative signals were observed in adjacent retinal areas. The hemodynamic changes showed time delays after stimulation. The signal magnitudes induced by light stimulation were observed in blood regions and did not show significant changes in blood-free regions. These differences may arise from different mechanisms in blood vessels and neural tissues in response to light stimulation. These characteristics agreed well with our previous observations in mouse retinas. Further development of the multimodal OCT may provide a new imaging method for studying how retinal structures and metabolic and neural functions are affected by age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), and other diseases, which promises novel noninvasive biomarkers for early disease detection and reliable treatment evaluations of eye diseases.

Unstable low-mass planetary systems as drivers of white dwarf pollution

Science.gov (United States)

Mustill, Alexander J.; Villaver, Eva; Veras, Dimitri; Gänsicke, Boris T.; Bonsor, Amy

2018-05-01

At least 25 {per cent} of white dwarfs show atmospheric pollution by metals, sometimes accompanied by detectable circumstellar dust/gas discs or (in the case of WD 1145+017) transiting disintegrating asteroids. Delivery of planetesimals to the white dwarf by orbiting planets is a leading candidate to explain these phenomena. Here, we study systems of planets and planetesimals undergoing planet-planet scattering triggered by the star's post-main-sequence mass loss, and test whether this can maintain high rates of delivery over the several Gyr that they are observed. We find that low-mass planets (Earth to Neptune mass) are efficient deliverers of material and can maintain the delivery for Gyr. Unstable low-mass planetary systems reproduce the observed delayed onset of significant accretion, as well as the slow decay in accretion rates at late times. Higher-mass planets are less efficient, and the delivery only lasts a relatively brief time before the planetesimal populations are cleared. The orbital inclinations of bodies as they cross the white dwarf's Roche limit are roughly isotropic, implying that significant collisional interactions of asteroids, debris streams and discs can be expected. If planet-planet scattering is indeed responsible for the pollution of white dwarfs, many such objects, and their main-sequence progenitors, can be expected to host (currently undetectable) super-Earth planets on orbits of several au and beyond.

Invasive hemodynamic characterization of heart failure with preserved ejection fraction

DEFF Research Database (Denmark)

Andersen, Mads Jønsson; Borlaug, Barry A

2014-01-01

Recent hemodynamic studies have advanced our understanding of heart failure with preserved ejection fraction (HFpEF). Despite improved pathophysiologic insight, clinical trials have failed to identify an effective treatment for HFpEF. Invasive hemodynamic assessment can diagnose or exclude HFp...

Hemodynamic study of cervical carotid arteries using DSA

International Nuclear Information System (INIS)

Kumashiro, Masayuki; Araki, Osamu; Matsunaga, Morio; Shigeyasu, Makio

1986-01-01

Although intravenous digital subtraction angiography (IVDSA) has been widely utilized as a means of morphological examination for the detection of intracranial or extracranial vascular lesions, it has thus for contributed little to quantitative assessment in hemodynamics. In the present study, a fundamental analysis of the hemodynamics on the cervical carotid artery was performed with a relative perfusion efficiency (Rath et al., 1979). This was not related to the measurement of time, such as the mean transit time, but was based on Sapirstein's principle. After the intravenous administration of the contrast material, dynamic DSA was performed using our equipment, Shimadzu DAR-100. After setting the region of interest in common carotid arteries on DSA images by means of a microdensitometer (Sakura PDS-15) combined with a computer (NEC ACOS-460), time-density curves were obtained on both sides. Thereafter, the RPE was calculated as a ratio of two integrals from the zero time to the earlier peak time of the time-density curves with respect to the time. The flow model with the hydro-dynamic system was used to detect the relationship between the RPEs and the ratios of the actual flows in the system. The results of this experiment showed a high correlation between the RPEs and the flows (r = 0.85, p < 0.001). In normal subjects (n = 28), the mean of the RPEs was 1.07 ± 0.27 (S.D.). The RPEs showed significantly lower values in the 5 patients with severe stenosis of the internal carotid artery (0.76 ± 0.15, p < 0.02), as well as even more significantly lower values in the 9 patients with a complete occlusion of the internal carotid artery (0.64 ± 0.19, p < 0.001). The RPE measurement with IVDSA has been shown to be useful for recognizing the cervical hemodynamic changes in patients with occlusive cervicovascular disease. (author)

Monitoring Detrusor Oxygenation and Hemodynamics Noninvasively during Dysfunctional Voiding

Science.gov (United States)

Macnab, Andrew J.; Stothers, Lynn S.; Shadgan, Babak

2012-01-01

The current literature indicates that lower urinary tract symptoms (LUTSs) related to benign prostatic hyperplasia (BPH) have a heterogeneous pathophysiology. Pressure flow studies (UDSs) remain the gold standard evaluation methodology for such patients. However, as the function of the detrusor muscle depends on its vasculature and perfusion, the underlying causes of LUTS likely include abnormalities of detrusor oxygenation and hemodynamics, and available treatment options include agents thought to act on the detrusor smooth muscle and/or vasculature. Hence, near infrared spectroscopy (NIRS), an established optical methodology for monitoring changes in tissue oxygenation and hemodynamics, has relevance as a means of expanding knowledge related to the pathophysiology of BPH and potential treatment options. This methodological report describes how to conduct simultaneous NIRS monitoring of detrusor oxygenation and hemodynamics during UDS, outlines the clinical implications and practical applications of NIRS, explains the principles of physiologic interpretation of NIRS voiding data, and proposes an exploratory hypothesis that the pathophysiological causes underlying LUTS include detrusor dysfunction due to an abnormal hemodynamic response or the onset of oxygen debt during voiding. PMID:23019422

Monitoring Detrusor Oxygenation and Hemodynamics Noninvasively during Dysfunctional Voiding

Directory of Open Access Journals (Sweden)

Andrew J. Macnab

2012-01-01

Full Text Available The current literature indicates that lower urinary tract symptoms (LUTSs related to benign prostatic hyperplasia (BPH have a heterogeneous pathophysiology. Pressure flow studies (UDSs remain the gold standard evaluation methodology for such patients. However, as the function of the detrusor muscle depends on its vasculature and perfusion, the underlying causes of LUTS likely include abnormalities of detrusor oxygenation and hemodynamics, and available treatment options include agents thought to act on the detrusor smooth muscle and/or vasculature. Hence, near infrared spectroscopy (NIRS, an established optical methodology for monitoring changes in tissue oxygenation and hemodynamics, has relevance as a means of expanding knowledge related to the pathophysiology of BPH and potential treatment options. This methodological report describes how to conduct simultaneous NIRS monitoring of detrusor oxygenation and hemodynamics during UDS, outlines the clinical implications and practical applications of NIRS, explains the principles of physiologic interpretation of NIRS voiding data, and proposes an exploratory hypothesis that the pathophysiological causes underlying LUTS include detrusor dysfunction due to an abnormal hemodynamic response or the onset of oxygen debt during voiding.

White-collar workers' hemodynamic responses during working hours.

Science.gov (United States)

Liu, Xinxin; Iwakiri, Kazuyuki; Sotoyama, Midori

2017-08-08

In the present study, two investigations were conducted at a communication center, to examine white-collar workers' hemodynamic responses during working hours. In investigation I, hemodynamic responses were measured on a working day; and in investigation II, cardiovascular responses were verified on both working and non-working days. In investigation I, blood pressure, cardiac output, heart rate, stroke volume, and total peripheral resistance were measured in 15 workers during working hours (from 9:00 am to 18:00 pm) on one working day. Another 40 workers from the same workplace participated in investigation II, in which blood pressure and heart rate were measured between the time workers arose in the morning until they went to bed on 5 working days and 2 non-working days. The results showed that blood pressure increased and remained at the same level during working hours. The underlying hemodynamics of maintaining blood pressure, however, changed between the morning and the afternoon on working days. Cardiac responses increased in the afternoon, suggesting that cardiac burdens increase in the afternoon on working days. The present study suggested that taking underlying hemodynamic response into consideration is important for managing the work-related cardiovascular burden of white-collar workers.

Permanent education that approaches radiation protection in hemodynamic service

International Nuclear Information System (INIS)

Flor, Rita de Cassia; Anjos, Djeniffer Valdirene dos

2011-01-01

In the hemodynamic services that apply ionizing radiation yet exist the necessity of capacitation of workers for actuation in those areas. So, this qualitative study performed in a hemodynamic service at Sao Jose, Santa Catarina, Brazil, had the objective to analyse how are developed the permanent education programs and the real necessity of workers. The results have shown that the workers are longing for their qualification and formation, as generally they are admitted with not any qualification for those services. So, the workers that realize the on duty hemodynamic service praxis must do it in a conscious manner and the E P is a way for to adopt good practice in radiological protection

Unstable volatility

DEFF Research Database (Denmark)

Casas, Isabel; Gijbels, Irène

2012-01-01

The objective of this paper is to introduce the break-preserving local linear (BPLL) estimator for the estimation of unstable volatility functions for independent and asymptotically independent processes. Breaks in the structure of the conditional mean and/or the volatility functions are common...... in Finance. Nonparametric estimators are well suited for these events due to the flexibility of their functional form and their good asymptotic properties. However, the local polynomial kernel estimators are not consistent at points where the volatility function has a break. The estimator presented...

Development of BOLD signal hemodynamic responses in the human brain

NARCIS (Netherlands)

Arichi, T.; Varela, M.; Melendez-Calderon, A.; Allievi, A.; Merchant, N.; Tusor, N.; Counsell, S.J.; Burdet, E.; Beckmann, Christian; Edwards, A.D.

2012-01-01

In the rodent brain the hemodynamic response to a brief external stimulus changes significantly during development. Analogous changes in human infants would complicate the determination and use of the hemodynamic response function (HRF) for functional magnetic resonance imaging (fMRI) in developing

Echographic and hemodynamic parameters in patients with hepatic cirrhosis and portal hypertension

International Nuclear Information System (INIS)

Rikhsieva, L.Eh.; Akhmedzhanova, Sh.Sh.; Myasnik, B.N.; Khodzhibekov, M.Kh.

1989-01-01

The efficiency of combined echoradionuclide investigation for the identification of the severity of portal hypertension and the determination of clear-cut criteria for the differentiation of stages of portal hypertension with reference to functional potentials of renal hemodynamics and systemic circulation at large is demonstrated

Nuclear data for unstable isotopes

International Nuclear Information System (INIS)

Sorlin, O.

1992-01-01

Nuclear Physics and Astrophysics are both entrusted with the task of understanding nucleosynthesis and energy production in the stars. At high temperatures and densities present in explosive scenarii such as the early universe, cataclysmic binary stars (nova or accretion stars), and supernovae, the nucleosynthesis proceeds throughout unstable nuclei. In order to produce and to study the most exotic isotopes that are not accessible from stable beam - stable (or radioactive) target experiments, it is necessary to develop facilities that utilize Radioactive Nuclear Beams (RNB). The existing methods for producing unstable nuclei will be described in paragraph 2. A review of the major explosive stellar processes will be made through some selected examples using RNB

Sutudy on exchange flow under the unstably stratified field

OpenAIRE

文沢, 元雄

2005-01-01

This paper deals with the exchange flow under the unstably stratified field. The author developed the effective measurement system as well as the numerical analysis program. The system and the program are applied to the helium-air exchange flow in a rectangular channel with inclination. Following main features of the exchange flow were discussed based on the calculated results.(1) Time required for establishing a quasi-steady state exchange flow.(2) The relationship between the inclination an...

Stable, metastable and unstable solutions of a spin-1 Ising system based on the free energy surfaces

Science.gov (United States)

Keskİin, Mustafa; Özgan, Şükrü

1990-04-01

Stable, metastable and unstable solutions of a spin-1 Ising model with bilinear and biquadratic interactions are found by using the free energy surfaces. The free energy expression is obtained in the lowest approximation of the cluster variation method. All these solutions are shown in the two-dimensional phase space, especially the unstable solutions which in some cases are difficult to illustrate in the two-dimensional phase space, found by Keskin et al. recently.

Biology and hemodynamics of aneurismal vasculopathies

International Nuclear Information System (INIS)

Pereira, Vitor Mendes; Brina, Olivier; Gonzalez, Ana Marcos; Narata, Ana Paula; Ouared, Rafik; Karl-Olof, Lovblad

2013-01-01

Aneurysm vasculopathies represents a group of vascular disorders that share a common morphological diagnosis: a vascular dilation, the aneurysm. They can have a same etiology and a different clinical presentation or morphology, or have different etiology and very similar anatomical geometry. The biology of the aneurysm formation is a complex process that will be a result of an endogenous predisposition and epigenetic factors later on including the intracranial hemodynamics. We describe the biology of saccular aneurysms, its growth and rupture, as well as, current concepts of hemodynamics derived from application of computational flow dynamics on patient specific vascular models. Furthermore, we describe different aneurysm phenotypes and its extremely variability on morphological and etiological presentation

Evaluation of plain radiograph in mitral stenosis related to hemodynamics

International Nuclear Information System (INIS)

Choe, Ku Ok; Suh, Jung Ho; Park, Chang Yun; Choi, Byung So

1973-01-01

Mitral stenosis, the most frequent heart disease in adult, showed relatively characteristic pulmonary findings in plain chest X-ray. In recent years the knowledge of the altered physiology of hemodynamics could offer considerable amount of hemodynamic barrier in plain chest. But the value of several parameters was still controversial. In this study a variety of roentgen signs were related to physiologic data and those were acquired by the cardiac catheterization in total of 67 cases of mitral stenosis. 1. Correlation of DPA/DHT ratio (Diameter of pulmonary arterial segment/ Diameter of hemithorax X 100) to hemodynamic data; The pulmonary arterial segments was dilated by two factors, the one was pulmonary blood flow and the other the blood pressure within it. In mitral stenosis, the cardiac output was decreased to quite uniform level, hence measurement of pulmonary arterial segment might be valuable. The correlation coefficient of DPA/ DHT ratio to hemodynamic data were as follows: 0.54 to mean pulmonary artery pressure, 0.32 to pulmonary capillary wedge pressure, -0.37 to mitral valvular area and 0.07 to pulmonary vascular resistance. No significant difference was noted in between pure mitral stenosis and mitral stenosis associated with other valvular disease. 2. Correlation of diameter of right descending pulmonary artery to hemodynamic data: The measurement was made near the first bifurcation of right descending pulmonary artery at its widest point. Pulmonary vascular pattern was best correlated (r=0.71). Another had rough correlation: 0.05 to mean pulmonary artery pressure, 0.31 to pulmonary capillary wedge pressure, -0.44 to mitral valvular area in correlation coefficient. No pulmonary arterial hypertension was observed in the cases diameter of less than 12 mm, but all except two cases had pulmonary hypertension in which diameter exceeded 16 mm. According to increase of the mean pulmonary arterial pressure, the same increment in pressure increased change

Evaluation of plain radiograph in mitral stenosis related to hemodynamics

Energy Technology Data Exchange (ETDEWEB)

Choe, Ku Ok; Suh, Jung Ho; Park, Chang Yun; Choi, Byung So [Yonsei University College of Medicine, Seoul (Korea, Republic of)

1973-04-15

Mitral stenosis, the most frequent heart disease in adult, showed relatively characteristic pulmonary findings in plain chest X-ray. In recent years the knowledge of the altered physiology of hemodynamics could offer considerable amount of hemodynamic barrier in plain chest. But the value of several parameters was still controversial. In this study a variety of roentgen signs were related to physiologic data and those were acquired by the cardiac catheterization in total of 67 cases of mitral stenosis. 1. Correlation of DPA/DHT ratio (Diameter of pulmonary arterial segment/ Diameter of hemithorax X 100) to hemodynamic data; The pulmonary arterial segments was dilated by two factors, the one was pulmonary blood flow and the other the blood pressure within it. In mitral stenosis, the cardiac output was decreased to quite uniform level, hence measurement of pulmonary arterial segment might be valuable. The correlation coefficient of DPA/ DHT ratio to hemodynamic data were as follows: 0.54 to mean pulmonary artery pressure, 0.32 to pulmonary capillary wedge pressure, -0.37 to mitral valvular area and 0.07 to pulmonary vascular resistance. No significant difference was noted in between pure mitral stenosis and mitral stenosis associated with other valvular disease. 2. Correlation of diameter of right descending pulmonary artery to hemodynamic data: The measurement was made near the first bifurcation of right descending pulmonary artery at its widest point. Pulmonary vascular pattern was best correlated (r=0.71). Another had rough correlation: 0.05 to mean pulmonary artery pressure, 0.31 to pulmonary capillary wedge pressure, -0.44 to mitral valvular area in correlation coefficient. No pulmonary arterial hypertension was observed in the cases diameter of less than 12 mm, but all except two cases had pulmonary hypertension in which diameter exceeded 16 mm. According to increase of the mean pulmonary arterial pressure, the same increment in pressure increased change

Hemodynamic imaging of cerebrovascular disease

Energy Technology Data Exchange (ETDEWEB)

Grond, J. van der; Hendrikse, J.; Osch, M.J.P. van [Dept. of Radiology, University Hospital Utrecht (Netherlands)

2001-11-01

MR can provide data on perfusion, oxygen consumption and oxygen metabolism, which can be of great value in stroke research. This article reviews the possibilities and current status of the MR techniques with respect to intracranial hemodynamic changes. (orig.)

Does the renin-angiotensin system determine the renal and systemic hemodynamic response to sodium in patients with essential hypertension?

NARCIS (Netherlands)

vanPaassen, P; deZeeuw, D; Navis, G; deJong, PE

Many patients with essential hypertension respond to a high dietary sodium intake with a rise in blood pressure. Experimental evidence suggests that the renal hemodynamic response to sodium determines, at least partially, this rise in blood pressure. Our aim was to clarify the role of the

Usefulness of PiCCO in the management of patients with delayed vasospasm after subarachnoid hemorrhage. From a viewpoint of systemic cardiovascular hemodynamics

International Nuclear Information System (INIS)

Takayanagi, Shunsaku; Sakamoto, Masayuki; Kamijoh, Koji

2008-01-01

Before the PiCCO system became available, patients with delayed vasospasm were treated in order to control circulating blood volume from the viewpoint of several systemic factors associated with pressure such as central venous pressure, pulmonary arterial wedged pressure, etc. Since, however, these factors are well-known to not always reflect the circulating blood volume excessive intravenous administration induces over-hydration in patients who are either aged and/or are experiencing symptomatic vasospasm, leading to serious conditions such as pulmonary edema and cardiac failure. The PiCCO system has enabled us to treat patients with symptomatic vasospasm by more precisely estimating circulating hemodynamics. Taking into account the data obtained from the PiCCO system, we discuss its advantages and disadvantages. Out of patients who underwent acute surgery from June 2006 to May 2007, a total of 18 patients with Fisher 3 in CT grading of SAH who were thought to be likely to suffer from cardiac failure or pulmonary edema were selected. The average age was 63.2. The number of patients of preoperative Hunt and Kosnik Grade II, III, IV and V was 3, 10, 3 and 2, respectively. Angiographic vasospasm was revealed in 10 patients, 7 of whom were symptomatic. The in- and out-put control in these 18 patients was executed using the PiCCO system. None showed clinical symptoms associated with cardiac failure or pulmonary edema. We conclude that the PiCCO system is very useful to control the systemic hemodynamics in the treatment of patients with delayed vasospasm. (author)

New approach to intracardiac hemodynamic measurements in small animals

DEFF Research Database (Denmark)

Eskesen, Kristian; Olsen, Niels T; Dimaano, Veronica L

2012-01-01

Invasive measurements of intracardiac hemodynamics in animal models have allowed important advances in the understanding of cardiac disease. Currently they are performed either through a carotid arteriotomy or via a thoracotomy and apical insertion. Both of these techniques have disadvantages...... and are not conducive to repeated measurements. Therefore, the purpose of this study was to develop a new technique for measuring intracardiac hemodynamics....

Neural-net based unstable machine identification using individual energy functions. [Transient disturbances in power systems

Energy Technology Data Exchange (ETDEWEB)

Djukanovic, M [Institut Nikola Tesla, Belgrade (Yugoslavia); Sobajic, D J; Pao, Yohhan [Case Western Reserve Univ., Cleveland, OH (United States)

1991-10-01

The identification of the mode of instability plays an essential role in generating principal energy boundary hypersurfaces. We present a new method for unstable machine identification based on the use of supervised learning neural-net technology, and the adaptive pattern recognition concept. It is shown that using individual energy functions as pattern features, appropriately trained neural-nets can retrieve the reliable characterization of the transient process including critical clearing time parameter, mode of instability and energy margins. Generalization capabilities of the neural-net processing allow for these assessments to be made independently of load levels. The results obtained from computer simulations are presented using the New England power system, as an example. (author).

Study on unstable fracture characteristics of light water reactor piping

International Nuclear Information System (INIS)

Kurihara, Ryoichi

1998-08-01

Many testing studies have been conducted to validate the applicability of the leak before break (LBB) concept for the light water reactor piping in the world. It is especially important among them to clarify the condition that an inside surface crack of the piping wall does not cause an unstable fracture but ends in a stable fracture propagating only in the pipe thickness direction, even if the excessive loading works to the pipe. Pipe unstable fracture tests performed in Japan Atomic Energy Research Institute had been planned under such background, and clarified the condition for the cracked pipe to cause the unstable fracture under monotonous increase loading or cyclic loading by using test pipes with the inside circumferential surface crack. This paper examines the pipe unstable fracture by dividing it into two parts. One is the static unstable fracture that breaks the pipe with the inside circumferential surface crack by increasing load monotonously. Another is the dynamic unstable fracture that breaks the pipe by the cyclic loading. (author). 79 refs

The effect of nonlinearity on unstable zones of Mathieu equation

Indian Academy of Sciences (India)

2017-02-09

Feb 9, 2017 ... Abstract. Mathieu equation is a well-known ordinary differential equation in which the excitation term appears as the non-constant coefficient. The mathematical modelling of many dynamic systems leads to Mathieu equation. The determination of the locus of unstable zone is important for the control of ...

Lyapunov vectors and assimilation in the unstable subspace: theory and applications

International Nuclear Information System (INIS)

Palatella, Luigi; Carrassi, Alberto; Trevisan, Anna

2013-01-01

Based on a limited number of noisy observations, estimation algorithms provide a complete description of the state of a system at current time. Estimation algorithms that go under the name of assimilation in the unstable subspace (AUS) exploit the nonlinear stability properties of the forecasting model in their formulation. Errors that grow due to sensitivity to initial conditions are efficiently removed by confining the analysis solution in the unstable and neutral subspace of the system, the subspace spanned by Lyapunov vectors with positive and zero exponents, while the observational noise does not disturb the system along the stable directions. The formulation of the AUS approach in the context of four-dimensional variational assimilation (4DVar-AUS) and the extended Kalman filter (EKF-AUS) and its application to chaotic models is reviewed. In both instances, the AUS algorithms are at least as efficient but simpler to implement and computationally less demanding than their original counterparts. As predicted by the theory when error dynamics is linear, the optimal subspace dimension for 4DVar-AUS is given by the number of positive and null Lyapunov exponents, while the EKF-AUS algorithm, using the same unstable and neutral subspace, recovers the solution of the full EKF algorithm, but dealing with error covariance matrices of a much smaller dimension and significantly reducing the computational burden. Examples of the application to a simplified model of the atmospheric circulation and to the optimal velocity model for traffic dynamics are given. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Lyapunov analysis: from dynamical systems theory to applications’. (paper)

Output Error Method for Tiltrotor Unstable in Hover

Directory of Open Access Journals (Sweden)

Lichota Piotr

2017-03-01

Full Text Available This article investigates unstable tiltrotor in hover system identification from flight test data. The aircraft dynamics was described by a linear model defined in Body-Fixed-Coordinate System. Output Error Method was selected in order to obtain stability and control derivatives in lateral motion. For estimating model parameters both time and frequency domain formulations were applied. To improve the system identification performed in the time domain, a stabilization matrix was included for evaluating the states. In the end, estimates obtained from various Output Error Method formulations were compared in terms of parameters accuracy and time histories. Evaluations were performed in MATLAB R2009b environment.

Hemodynamics in patients with hypertensive intracerebral hemorrhage

International Nuclear Information System (INIS)

Kitahara, Tetsuhiro

1997-01-01

Cerebral hemodynamics in 15 patients with hypertensive intracerebral hemorrhage (HICH) were evaluated by measuring cerebral blood flow (CBF) and cerebrovascular reserve capacity, using stable xenon-enhanced computed tomography. Their hematomas were removed by stereotactic aqua stream aspiration. The hemispheric and thalamic CBFs of patients with HICH were lower than those of hypertensive patients without hematomas. However, the hemispheric CBF increased according to how much of the hematoma was removed surgically. Thus, hemodynamics in patients with HICH can be improved by surgical hematoma removal, although some adjunct therapies are necessary in order to prevent secondary edema and the delayed neuronal death. (author)

In vivo measurement of hemodynamic information in stenosed rat blood vessels using X-ray PIV.

Science.gov (United States)

Park, Hanwook; Park, Jun Hong; Lee, Sang Joon

2016-11-28

Measurements of the hemodynamic information of blood flows, especially wall shear stress (WSS), in animal models with circulatory vascular diseases (CVDs) are important to understand the pathological mechanism of CVDs. In this study, X-ray particle image velocimetry (PIV) with high spatial resolution was applied to obtain velocity field information in stenosed blood vessels with high WSS. 3D clips fabricated with a 3D printer were applied to the abdominal aorta of a rat cadaver to induce artificial stenosis in the real blood vessel of an animal model. The velocity and WSS information of blood flows in the stenosed vessel were obtained and compared at various stenosis severities. In vivo measurement was also conducted by fastening a stenotic clip on a live rat model through surgical intervention to reduce the flow rate to match the limited temporal resolution of the present X-ray PIV system. Further improvement of the temporal resolution of the system might be able to provide in vivo measurements of hemodynamic information from animal disease models under physiological conditions. The present results would be helpful for understanding the relation between hemodynamic characteristics and the pathological mechanism in animal CVD models.

[Meta-analyses on measurement precision of non-invasive hemodynamic monitoring technologies in adults].

Science.gov (United States)

Pestel, G; Fukui, K; Higashi, M; Schmidtmann, I; Werner, C

2018-06-01

An ideal non-invasive monitoring system should provide accurate and reproducible measurements of clinically relevant variables that enables clinicians to guide therapy accordingly. The monitor should be rapid, easy to use, readily available at the bedside, operator-independent, cost-effective and should have a minimal risk and side effect profile for patients. An example is the introduction of pulse oximetry, which has become established for non-invasive monitoring of oxygenation worldwide. A corresponding non-invasive monitoring of hemodynamics and perfusion could optimize the anesthesiological treatment to the needs in individual cases. In recent years several non-invasive technologies to monitor hemodynamics in the perioperative setting have been introduced: suprasternal Doppler ultrasound, modified windkessel function, pulse wave transit time, radial artery tonometry, thoracic bioimpedance, endotracheal bioimpedance, bioreactance, and partial CO 2 rebreathing have been tested for monitoring cardiac output or stroke volume. The photoelectric finger blood volume clamp technique and respiratory variation of the plethysmography curve have been assessed for monitoring fluid responsiveness. In this manuscript meta-analyses of non-invasive monitoring technologies were performed when non-invasive monitoring technology and reference technology were comparable. The primary evaluation criterion for all studies screened was a Bland-Altman analysis. Experimental and pediatric studies were excluded, as were all studies without a non-invasive monitoring technique or studies without evaluation of cardiac output/stroke volume or fluid responsiveness. Most studies found an acceptable bias with wide limits of agreement. Thus, most non-invasive hemodynamic monitoring technologies cannot be considered to be equivalent to the respective reference method. Studies testing the impact of non-invasive hemodynamic monitoring technologies as a trend evaluation on outcome, as well as

Computational simulation of passive leg-raising effects on hemodynamics during cardiopulmonary resuscitation.

Science.gov (United States)

Shin, Dong Ah; Park, Jiheum; Lee, Jung Chan; Shin, Sang Do; Kim, Hee Chan

2017-03-01

The passive leg-raising (PLR) maneuver has been used for patients with circulatory failure to improve hemodynamic responsiveness by increasing cardiac output, which should also be beneficial and may exert synergetic effects during cardiopulmonary resuscitation (CPR). However, the impact of the PLR maneuver on CPR remains unclear due to difficulties in monitoring cardiac output in real-time during CPR and a lack of clinical evidence. We developed a computational model that couples hemodynamic behavior during standard CPR and the PLR maneuver, and simulated the model by applying different angles of leg raising from 0° to 90° and compression rates from 80/min to 160/min. The simulation results showed that the PLR maneuver during CPR significantly improves cardiac output (CO), systemic perfusion pressure (SPP) and coronary perfusion pressure (CPP) by ∼40-65% particularly under the recommended range of compression rates between 100/min and 120/min with 45° of leg raise, compared to standard CPR. However, such effects start to wane with further leg lifts, indicating the existence of an optimal angle of leg raise for each person to achieve the best hemodynamic responses. We developed a CPR-PLR model and demonstrated the effects of PLR on hemodynamics by investigating changes in CO, SPP, and CPP under different compression rates and angles of leg raising. Our computational model will facilitate study of PLR effects during CPR and the development of an advanced model combined with circulatory disorders, which will be a valuable asset for further studies. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Management of acute unstable acromioclavicular joint injuries.

Science.gov (United States)

Cisneros, Luis Natera; Reiriz, Juan Sarasquete

2016-12-01

Surgical management of acute unstable acromioclavicular joint injuries should be focused on realigning the torn ends of the ligaments to allow for healing potential. The most widely utilized treatment methods incorporate the use of metal hardware, which can alter the biomechanics of the acromioclavicular joint. This leads to a second surgical procedure for hardware removal once the ligaments have healed. Patients with unstable acromioclavicular joint injuries managed with arthroscopy-assisted procedures have shown good and excellent clinical outcomes, without the need for a second operation. These procedures incorporate a coracoclavicular suspension device aimed to function as an internal brace, narrowing the coracoclavicular space thus allowing for healing of the torn coracoclavicular ligaments. The lesser morbidity of a minimally invasive approach and the possibility to diagnose and treat concomitant intraarticular injuries; no obligatory implant removal, and the possibility of having a straight visualization of the inferior aspect of the base of the coracoid (convenient when placing coracoclavicular fixation systems) are the main advantages of the arthroscopic approach over classic open procedures. This article consists on a narrative review of the literature in regard to the management of acute acromioclavicular joint instability.

Unstable fracture of nuclear pressure vessel

International Nuclear Information System (INIS)

Urata, Kazuyoshi

1978-01-01

Unstable fracture of nuclear pressure vessel shell for light water reactors up to 1,000 MWe class is discussed in accordance with ASME Code Sec. XI. The depth of surface crack required to protect against the unstable fracture is calculated on the basis of reactor operating conditions including loss of coolant accidents. Calculated surface crack depth a is equal to tαexp(2.19(a/l)) where l is crack length and t is weld thickness. α is crack depth required to protect against the unstable fracture in terms of the ratio of crack deth to weld thickness for surface crack have infinite length. Using this α, the safety factor included for allowable defect described in Sec. XI and the effects of thickness is discussed. It is derived that allowable defect described in Sec. XI include the safety factor of two on the crack depth for crack initiation at postulated accident and the safety factor of ten for crack depth calculated from point of view of crack arrest at normal conditions. (auth.)

Post-Treatment Hemodynamics of a Basilar Aneurysm and Bifurcation

Energy Technology Data Exchange (ETDEWEB)

Ortega, J; Hartman, J; Rodriguez, J; Maitland, D

2008-01-16

Aneurysm re-growth and rupture can sometimes unexpectedly occur following treatment procedures that were initially considered to be successful at the time of treatment and post-operative angiography. In some cases, this can be attributed to surgical clip slippage or endovascular coil compaction. However, there are other cases in which the treatment devices function properly. In these instances, the subsequent complications are due to other factors, perhaps one of which is the post-treatment hemodynamic stress. To investigate whether or not a treatment procedure can subject the parent artery to harmful hemodynamic stresses, computational fluid dynamics simulations are performed on a patient-specific basilar aneurysm and bifurcation before and after a virtual endovascular treatment. The simulations demonstrate that the treatment procedure produces a substantial increase in the wall shear stress. Analysis of the post-treatment flow field indicates that the increase in wall shear stress is due to the impingement of the basilar artery flow upon the aneurysm filling material and to the close proximity of a vortex tube to the artery wall. Calculation of the time-averaged wall shear stress shows that there is a region of the artery exposed to a level of wall shear stress that can cause severe damage to endothelial cells. The results of this study demonstrate that it is possible for a treatment procedure, which successfully excludes the aneurysm from the vascular system and leaves no aneurysm neck remnant, to elevate the hemodynamic stresses to levels that are injurious to the immediately adjacent vessel wall.

Unstable ductile fracture conditions in upper shelf region

International Nuclear Information System (INIS)

Nakano, Yoshifumi; Kubo, Takahiro

1985-01-01

The phenomenon of unstability of ductile fracture in the upper shelf region of a forged steel for nuclear reactor pressure vessels A508 Cl. 3 was studied with a large compliance apparatus, whose spring constants were 100, 170 and 230 kgf/mm, at the test temperatures of 100, 200 and 300 0 C and at the loading rates of 2, 20 and 200 mm/min in the crosshead speed. The main results obtained are as follows: (1) The fracture modes of the specimens consisted of (a) stable fracture, (b) unstable fracture which leads to a complete fracture rapidly and (c) quasiunstable fracture which does not lead to a complete fracture though a rapid extension of ductile crack takes place. (2) Side groove, high temperature or small spring constant made a ductile crack more unstable. (3) High temperature or large spring constant made the occurrence of quasiunstable fracture easier. (4) Quasiunstable ductile fracture took place before the maximum load, that is, at the J integral value of about 10 kgf/mm. The initiation of a microscopic ductile crack, therefore, seems to lead to quasiunstable fracture. (5) The concept that unstable ductile fracture takes place when Tsub(app) exceeds Tsub(mat) seems applicable only to the case in which unstable ductile fracture takes place after the maximum load has been exceeded. (author)

Radiation protection in hemodynamics work process: the look of the multidisciplinary team

International Nuclear Information System (INIS)

Borges, Laurete Medeiros; Klauberg, Daniela; Huhn, Andrea; Melo, Juliana Almeida Coelho de

2014-01-01

The study was conducted in a hemodynamics service of a public hospital in Florianopolis, SC, Brazil. Qualitative research with the participation of 13 professionals from a multidisciplinary team: doctors, technicians, technologists in radiology and nurses. The research material was extracted from the observations, semi-structured interviews and documentary analysis. The responses were grouped into three categories relating to: training of hemodynamic professionals and the perception of radiological protection in the work process; occupational exposure and safety of the professionals of Hemodynamics; and continuing education in hemodynamic service. Professionals are daily exposed to ionizing radiation, and for being long procedures, lead to high levels of exposure in workers. In hemodynamic services the risk of biological effects are cumulative, because radiodiagnostic procedures include issuing the higher doses of ionizing radiation in which the personnel exposure is critical. The workforce in the service researched mostly consists of technical professionals who reported little knowledge of radiation protection and ionizing radiation and that this issue was not addressed during their training. However, despite mention little knowledge about radiological protection, participants demonstrated understand the biological effects, especially with regard to pathologies caused by frequent exposure without protection to ionizing radiation. These professionals said they have no knowledge of the proper use of radiological protection equipment and the dosimeter, and that the institution does not provide all individual protective equipment required for the procedures performed in the hemodynamic service. Permanent education in hemodynamic service is very important part in the work process, though, cited by participants as little effectiveness in the institution, even when the professionals show interest in the area. Knowledge of the team providing hemodynamic service calls

Estimation Methods for Infinite-Dimensional Systems Applied to the Hemodynamic Response in the Brain

KAUST Repository

Belkhatir, Zehor

2018-05-01

Infinite-Dimensional Systems (IDSs) which have been made possible by recent advances in mathematical and computational tools can be used to model complex real phenomena. However, due to physical, economic, or stringent non-invasive constraints on real systems, the underlying characteristics for mathematical models in general (and IDSs in particular) are often missing or subject to uncertainty. Therefore, developing efficient estimation techniques to extract missing pieces of information from available measurements is essential. The human brain is an example of IDSs with severe constraints on information collection from controlled experiments and invasive sensors. Investigating the intriguing modeling potential of the brain is, in fact, the main motivation for this work. Here, we will characterize the hemodynamic behavior of the brain using functional magnetic resonance imaging data. In this regard, we propose efficient estimation methods for two classes of IDSs, namely Partial Differential Equations (PDEs) and Fractional Differential Equations (FDEs). This work is divided into two parts. The first part addresses the joint estimation problem of the state, parameters, and input for a coupled second-order hyperbolic PDE and an infinite-dimensional ordinary differential equation using sampled-in-space measurements. Two estimation techniques are proposed: a Kalman-based algorithm that relies on a reduced finite-dimensional model of the IDS, and an infinite-dimensional adaptive estimator whose convergence proof is based on the Lyapunov approach. We study and discuss the identifiability of the unknown variables for both cases. The second part contributes to the development of estimation methods for FDEs where major challenges arise in estimating fractional differentiation orders and non-smooth pointwise inputs. First, we propose a fractional high-order sliding mode observer to jointly estimate the pseudo-state and input of commensurate FDEs. Second, we propose a

Hemodynamic pattern in myocardial infarction patients at the common stages of rehabilitation

International Nuclear Information System (INIS)

Perepech, N.B.

1986-01-01

Integrated body rheography, radiocardiography and radionuclide ventriculography were used to investigate hemodynamic changes in 101 myocardial infarction patients during the hospital stage of the disease. Changes in major hemodynamic parameters were demonstrated by the end of the 1st week and when walking was resumed. At the resumed-walking stage, the mechanism of declining stroke and cardiac indices was shown to depend on physical activation rates. Hemodynamic response is mostly conditioned by myocardial insufficiency when walking is resumed rapidly during the 2nd week, and by smaller venous return due to hypovolemia where it is resumed slowly during the 4th week. Expanding motion regimens at slow rates results in persistent hemodynamic disturbances in myocardial infarction patients

Unstable dynamics, nonequilibrium phases, and criticality in networked excitable media

International Nuclear Information System (INIS)

Franciscis, S. de; Torres, J. J.; Marro, J.

2010-01-01

Excitable systems are of great theoretical and practical interest in mathematics, physics, chemistry, and biology. Here, we numerically study models of excitable media, namely, networks whose nodes may occasionally be dormant and the connection weights are allowed to vary with the system activity on a short-time scale, which is a convenient and realistic representation. The resulting global activity is quite sensitive to stimuli and eventually becomes unstable also in the absence of any stimuli. Outstanding consequences of such unstable dynamics are the spontaneous occurrence of various nonequilibrium phases--including associative-memory phases and one in which the global activity wanders irregularly, e.g., chaotically among all or part of the dynamic attractors--and 1/f noise as the system is driven into the phase region corresponding to the most irregular behavior. A net result is resilience which results in an efficient search in the model attractor space that can explain the origin of some observed behavior in neural, genetic, and ill-condensed matter systems. By extensive computer simulation we also address a previously conjectured relation between observed power-law distributions and the possible occurrence of a ''critical state'' during functionality of, e.g., cortical networks, and describe the precise nature of such criticality in the model which may serve to guide future experiments.

Magnetic resonance imaging based noninvasive measurements of brain hemodynamics in neonates

DEFF Research Database (Denmark)

De Vis, Jill B; Alderliesten, Thomas; Hendrikse, Jeroen

2016-01-01

Perinatal disturbances of brain hemodynamics can have a detrimental effect on the brain's parenchyma with consequently adverse neurodevelopmental outcome. Noninvasive, reliable tools to evaluate the neonate's brain hemodynamics are scarce. Advances in magnetic resonance imaging have provided new...

Acute coronary hemodynamic effects of equihypotensive doses of nisoldipine and diltiazem

NARCIS (Netherlands)

H. Suryapranata (Harry); P.W.J.C. Serruys (Patrick); A.L. Soward; J. Planellas; G. Vanhaleweyk; P.G. Hugenholtz (Paul)

1985-01-01

textabstractThe hemodynamic effects of nisoldipine and diltiazem were investigated in two groups of patients undergoing investigation for suspected coronary artery disease. Emphasis was placed on the coronary hemodynamic changes. Approximately equihypotensive doses of these two calcium channel

Rock slope instabilities in Norway: First systematic hazard and risk classification of 22 unstable rock slopes

Science.gov (United States)

Böhme, Martina; Hermanns, Reginald L.; Oppikofer, Thierry; Penna, Ivanna

2016-04-01

Unstable rock slopes that can cause large failures of the rock-avalanche type have been mapped in Norway for almost two decades. Four sites have earlier been characterized as high-risk objects based on expertise of few researchers. This resulted in installing continuous monitoring systems and set-up of an early-warning system for those four sites. Other unstable rock slopes have not been ranked related to their hazard or risk. There are ca. 300 other sites known of which 70 sites were installed for periodic deformation measurements using multiple techniques (Global Navigation Satellite Systems, extensometers, measurement bolts, and others). In 2012 a systematic hazard and risk classification system for unstable rock slopes was established in Norway and the mapping approach adapted to that in 2013. Now, the first 22 sites were classified for hazard, consequences and risk using this classification system. The selection of the first group of sites to be classified was based on an assumed high hazard or risk and importance given to the sites by Norwegian media and the public. Nine of the classified 22 unstable rock slopes are large sites that deform inhomogeneously or are strongly broken up in individual blocks. This suggests that different failure scenarios are possible that need to be analyzed individually. A total of 35 failure scenarios for those nine unstable rock slopes were considered. The hazard analyses were based on 9 geological parameters defined in the classification system. The classification system will be presented based on the Gamanjunni unstable rock slope. This slope has a well developed back scarp that exposes 150 m preceding displacement. The lateral limits of the unstable slope are clearly visible in the morphology and InSAR displacement data. There have been no single structures observed that allow sliding kinematically. The lower extend of the displacing rock mass is clearly defined in InSAR data and by a zone of higher rock fall activity. Yearly

Hemodynamic behavior modeling of a Virtual Surgical Patient based on a Fuzzy Expert System.

Directory of Open Access Journals (Sweden)

Paulo Farias Paiva

2016-07-01

Full Text Available The Virtual Reality (VR allows its users to experience a sense of being immersed in synthetic 3D scenarios generated by computer graphics. The so-called Virtual Environments (VEs based on RV can be applied to medical education, enabling: repetitive training and the development of psychomotor skills in surgical procedures without compromising real patients. Surgical simulators that feature Dynamic Virtual Patients (VPs, that is, reacts physiologically to interventions and medical decisions made during the training. These systems present more realism while it offers the possibility of varying clinical cases. This work has as main objective to discuss important issues of modeling the hemodynamic performance of a VP, specifically to simulate blood pressure values (both sistolic and diastolic variables. The model of a VP is presented as result as well as is presented an architecture for its integration to simulators based on VR.

Geography of resonances and Arnold diffusion in a priori unstable Hamiltonian systems

International Nuclear Information System (INIS)

Delshams, Amadeu; Huguet, Gemma

2009-01-01

In this paper we consider the case of a general C r+2 perturbation, for r large enough, of an a priori unstable Hamiltonian system of 2 + 1/2 degrees of freedom, and we provide explicit conditions on it, which turn out to be C 2 generic and are verifiable in concrete examples, which guarantee the existence of Arnold diffusion. This is a generalization of the result in Delshams et al (2006 Mem. Am. Math. Soc.) where the case of a perturbation with a finite number of harmonics in the angular variables was considered. The method of proof is based on a careful analysis of the geography of resonances created by a generic perturbation and it contains a deep quantitative description of the invariant objects generated by the resonances therein. The scattering map is used as an essential tool to construct transition chains of objects of different topology. The combination of quantitative expressions for both the geography of resonances and the scattering map provides, in a natural way, explicit computable conditions for instability

Hemodynamic causes of exercise intolerance in Fontan patients

DEFF Research Database (Denmark)

Hebert, Anders; Jensen, Annette S; Mikkelsen, Ulla Ramer

2014-01-01

BACKGROUND: Exercise intolerance is frequent among Fontan patients and an important determinant for quality of life. This study investigated the hemodynamic causes of impaired exercise capacity in Fontan patients with particular focus on the influence of stroke volume index (SVI) and heart rate (HR...... patients and controls respectively. CONCLUSION: SVI decreased significantly in Fontan patients near the end of maximal effort exercise. The low SVI at maximal exercise was the most important hemodynamic factor limiting exercise capacity in Fontan patients, whereas chronotropic impairment had a smaller...

Isotope shifts in unstable nuclei

International Nuclear Information System (INIS)

Rebel, H.

1980-05-01

Current experimental investigations of isotope shifts in atomic spectra of unstable nuclei and the resulting information about size and shape of nuclei far off stability are discussed with reference to some representative examples. (orig.)

Structure and clusters of light unstable nuclei

International Nuclear Information System (INIS)

En'yo, Yoshiko

2010-01-01

As it is known, cluster structures are often observed in light nuclei. In the recent evolution of unstable nuclear research (on nuclei having unbalanced number of neutron and proton) further new types of clusters are coming to be revealed. In this report, structures of light unstable nuclei and some of the theoretical models to describe them are reviewed. The following topics are picked up. 1. Cluster structure and theoretical models, 2. Cluster structure of unstable nuclei (low excited state). 3. Cluster structure of neutron excess beryllium isotopes. 4. Cluster gas like state in C isotope. 5. Dineutron structure of He isotopes. Numbers of strange nuclear structures of light nuclei are illustrated. Antisymmetrized molecular dynamics (AMD) is the recently developed theoretical framework which has been successfully used in heavy ion reactions and nuclear structure studies. Successful application of AMD to the isotopes of Be, B and C are illustrated. (S. Funahashi)

Emission temperatures from the decay of particle-unstable complex nuclei

International Nuclear Information System (INIS)

Nayak, T.K.

1990-01-01

Relative populations of particle-unstable states were measured for complex fragments emitted in the reaction 14 N + Ag at E/A = 35 MeV by using a position sensitive high resolution hodoscope. Experimental population probabilities of particle-unstable states were extracted by fitting the coincidence spectra of the decay products by an appropriate R-matrix or Breit-Wigner formalism. According to thermal models, the populations of excited states at freezeout are expected to follow a Boltzmann distribution weighted by the emission temperature of the system. Tests of this freezeout assumption were made by comparing the experimental population to the predictions of statistical calculations. Extensive statistical calculation which include the effect of sequential feeding from heavier particle unstable nuclei were performed to estimate the population probabilities and the ratios of population probabilities indicate emission temperatures of about 3-4 MeV. But a detailed comparison for individual fragments for a calculation with T em = 4 MeV reveals that about half of the measured population probabilities and one third of the ratios of the population probabilities differ significantly from the predictions of statistical calculations. Calculations which include rotational effects could not satisfactorily account for this discrepancy. These results suggest a possible breakdown of the assumption of local thermal equilibrium at freezeout

Analysis of Plasma Homocysteine Levels in Patients with Unstable Angina

Directory of Open Access Journals (Sweden)

José Roberto Tavares

2002-08-01

Full Text Available OBJECTIVE - To determine the prevalence of hyperhomocystinemia in patients with acute ischemic syndrome of the unstable angina type. METHODS - We prospectively studied 46 patients (24 females with unstable angina and 46 control patients (19 males, paired by sex and age, blinded to the laboratory data. Details of diets, smoking habits, medication used, body mass index, and the presence of hypertension and diabetes were recorded, as were plasma lipid and glucose levels, C-reactive protein, and lipoperoxidation in all participants. Patients with renal disease were excluded. Plasma homocysteine was estimated using high-pressure liquid chromatography. RESULTS - Plasma homocysteine levels were significantly higher in the group of patients with unstable angina (12.7±6.7 µmol/L than in the control group (8.7±4.4 µmol/L (p<0.05. Among males, homocystinemia was higher in the group with unstable angina than in the control group, but this difference was not statistically significant (14.1±5.9 µmol/L versus 11.9±4.2 µmol/L. Among females, however, a statistically significant difference was observed between the 2 groups: 11.0±7.4 µmol/L versus 6.4±2.9 µmol/L (p<0.05 in the unstable angina and control groups, respectively. Approximately 24% of the patients had unstable angina at homocysteine levels above 15 µmol/L. CONCLUSION - High homocysteine levels seem to be a relevant prevalent factor in the population with unstable angina, particularly among females.

Hemodynamic deterioration precedes onset of ventricular tachyarrhythmia after Heartmate II implantation.

Science.gov (United States)

Yaksh, Ameeta; Kik, Charles; Knops, Paul; Zwiers, Korinne; van Ettinger, Maarten J B; Manintveld, Olivier C; de Wijs, Marcel C J; van der Kemp, Peter; Bogers, Ad J J C; de Groot, Natasja M S

2016-07-08

Early postoperative ventricular tachyarrhythmia (PoVT) after left ventricular assist device (LVAD) implantation are common and associated with higher mortality-rates. At present, there is no data on initiation of these PoVT and the role of alterations in cardiac hemodynamics. A LVAD was implanted in a patient with end-stage heart failure due to a ischemic cardiomyopathy. Alterations in cardiac rhythm and hemodynamics preceding PoVT-episodes during the first five postoperative days were examined by using continuous recordings of cardiac rhythm and various hemodynamic parameters. All PoVT (N=120) were monomorphic, most often preceded by short-long-short-sequences or regular SR and initiated by ventricular runs. Prior to PoVT, mean arterial pressure decreased; heart rate and ST-segments deviations increased. PoVT are caused by different underlying electrophysiological mechanisms. Yet, they are all monomorphic and preceded by hemodynamic deterioration due to myocardial ischemia.

Intraosseous anesthesia in hemodynamic studies in children with cardiopathy.

Science.gov (United States)

Aliman, Ana Cristina; Piccioni, Marilde de Albuquerque; Piccioni, João Luiz; Oliva, José Luiz; Auler Júnior, José Otávio Costa

2011-01-01

Intraosseous (IO) access has been used with good results in emergency situations, when venous access is not available for fluids and drugs infusion. The objective of this study was to evaluate IO a useful technique for anesthesia and fluids infusion during hemodynamic studies and when peripheral intravascular access is unobtainable. The setting was an university hospital hemodynamics unit, and the subjects were twenty one infants with congenital heart disease enrolled for elective hemodynamic study diagnosis. This study compared the effectiveness of IO access in relation to IV access for infusion of anesthetics agents (ketamine, midazolam, and fentanyl) and fluids during hemodynamic studies. The anesthetic induction time, procedure duration, anesthesia recovery time, adequate hydration, and IV and IO puncture complications were compared between groups. The puncture time was significantly smaller in IO group (3.6 min) that in IV group (9.6 min). The anesthetic onset time (56.3 second) for the IV group was faster than IO group (71.3 second). No significant difference between groups were found in relation to hydration (IV group, 315.5 mL vs IO group, 293.2 mL), and anesthesia recovery time (IO group, 65.2 min vs IV group, 55.0 min). The puncture site was reevaluated after 7 and 15 days without signs of infection or other complications. Results showed superiority for IO infusion when considering the puncture time of the procedure. Due to its easy manipulation and efficiency, hydration and anesthesia by IO access was satisfactory for hemodynamic studies without the necessity of other infusion access. Copyright © 2011 Elsevier Editora Ltda. All rights reserved.

Proton scattering from unstable nuclei

Indian Academy of Sciences (India)

Recent improvements in the intensities and optical qualities of radioactive beams have made ... The quality of the data obtained are illustrated with recent results obtained at the GANIL facility for unstable oxygen, sulfur and argon isotopes.

Hemodynamic Based Coronary Artery Aneurysm Thrombosis Risk Stratification in Kawasaki Disease Patients

Science.gov (United States)

Grande Gutierrez, Noelia; Mathew, M.; McCrindle, B.; Kahn, A.; Burns, J.; Marsden, A.

2017-11-01

Coronary artery aneurysms (CAA) as a result of Kawasaki Disease (KD) put patients at risk for thrombosis and myocardial infarction. Current AHA guidelines recommend CAA diameter >8 mm or Z-score >10 as the criterion for initiating systemic anticoagulation. Our hypothesis is that hemodynamic data derived from computational blood flow simulations is a better predictor of thrombosis than aneurysm diameter alone. Patient-specific coronary models were constructed from CMRI for a cohort of 10 KD patients (5 confirmed thrombosis cases) and simulations with fluid structure interaction were performed using the stabilized finite element Navier-Stokes solver available in SimVascular. We used a closed-loop lumped parameter network (LPN) to model the heart and vascular boundary conditions coupled numerically to the flow solver. An automated parameter estimation method was used to match LPN values to clinical data for each patient. Hemodynamic data analysis resulted in low correlation between Wall Shear Stress (WSS)/ Particle Residence Time (PRT) and CAA diameter but demonstrates the positive correlation between hemodynamics and adverse patient outcomes. Our results suggest that quantifying WSS and PRT should enable identification of regions at higher risk of thrombosis. We propose a quantitative method to non-invasively assess the abnormal flow in CAA following KD that could potentially improve clinical decision-making regarding anticoagulation therapy.

Hemodynamics of a Patient-Specific Aneurysm Model with Proper Orthogonal Decomposition

Science.gov (United States)

Han, Suyue; Chang, Gary Han; Modarres-Sadeghi, Yahya

2017-11-01

Wall shear stress (WSS) and oscillatory shear index (OSI) are two of the most-widely studied hemodynamic quantities in cardiovascular systems that have been shown to have the ability to elicit biological responses of the arterial wall, which could be used to predict the aneurysm development and rupture. In this study, a reduced-order model (ROM) of the hemodynamics of a patient-specific cerebral aneurysm is studied. The snapshot Proper Orthogonal Decomposition (POD) is utilized to construct the reduced-order bases of the flow using a CFD training set with known inflow parameters. It was shown that the area of low WSS and high OSI is correlated to higher POD modes. The resulting ROM can reproduce both WSS and OSI computationally for future parametric studies with significantly less computational cost. Agreement was observed between the WSS and OSI values obtained using direct CFD results and ROM results.

[The effect of combined treatment with the use of magnetotherapy on the systemic hemodynamics of patients with ischemic heart disease and spinal osteochondrosis].

Science.gov (United States)

Dudchenko, M A; Vesel'skiĭ, I Sh; Shtompel', V Iu

1992-05-01

The authors examined 66 patients with ischemic heart disease and concomitant cervico-thoracic osteochondrosis and 22 patients without osteochondrosis. Differences were revealed in values of the systemic hemodynamics with prevalence of the hypokinetic type in patients with combined pathology. Inclusion of magnetotherapy in the treatment complex of patients with ischemic heart disease and osteochondrosis favours clinical improvement, normalization of indices of central and regional blood circulation.

Hemodynamic monitoring in different cortical layers with a single fiber optical system

Science.gov (United States)

Yu, Linhui; Noor, M. Sohail; Kiss, Zelma H. T.; Murari, Kartikeya

2018-02-01

Functional monitoring of highly-localized deep brain structures is of great interest. However, due to light scattering, optical methods have limited depth penetration or can only measure from a large volume. In this research, we demonstrate continuous measurement of hemodynamics in different cortical layers in response to thalamic deep brain stimulation (DBS) using a single fiber optical system. A 200-μm-core-diameter multimode fiber is used to deliver and collect light from tissue. The fiber probe can be stereotaxically implanted into the brain region of interest at any depth to measure the di use reflectance spectra from a tissue volume of 0.02-0.03 mm3 near the fiber tip. Oxygenation is then extracted from the reflectance spectra using an algorithm based on Monte Carlo simulations. Measurements were performed on the surface (cortical layer I) and at 1.5 mm depth (cortical layer VI) of the motor cortex in anesthetized rats with thalamic DBS. Preliminary results revealed the oxygenation changes in response to DBS. Moreover, the baseline as well as the stimulus-evoked change in oxygenation were different at the two depths of cortex.

Treatment options for unstable trochanteric fractures: Screw or helical proxima femoral nail.

Science.gov (United States)

Bajpai, Jeetendra; Maheshwari, Rajesh; Bajpai, Akansha; Saini, Sumit

2015-01-01

To compare treatment outcome of screw proximal femoral nail (PFN) system with that of a helical PFN. The study included 77 patients with closed unstable intertrochanteric fracture classified as AO 31A2&31A3, between June 2008 to August 2011. Inclusion criteria were: all mature skeletons above 50 years of age; closed unstable trochanteric fracture classified as AO 31A2&A3. Exclusion criteria were: immature skeleton, pathological fracture of any cause other than osteoporosis, inability to walk inde- pendently prior to injury. Patients were randomized to 2 treatment groups based on admission sequence. Forty patients were treated with screw PFN and thirty seven were treated with helical PFN. Both groups were similar in respect of time of surgery, blood loss and functional assessment and duration of hospitalization. In screw PFN group 2 patients had superficial wound infection, 1 patient had persistent hip pain and 1 patient had shortening>1 cm buttrochanteric fractures even in Indian patients where the bones are narrow and neck diameter is small. It is an implant of choice for osteoporotic and unstable trochanteric fractures.

Dynamics and statistics of unstable quantum states

International Nuclear Information System (INIS)

Sokolov, V.V.; Zelevinsky, V.G.

1989-01-01

The statistical theory of spectra formulated in terms of random matrices is extended to unstable states. The energies and widths of these states are treated as real and imaginary parts of complex eigenvalues for an effective non-hermitian hamiltonian. Eigenvalue statistics are investigated under simple assumptions. If the coupling through common decay channels is weak we obtain a Wigner distribution for the level spacings and a Porter-Thomas one for the widths, with the only exception for spacings less than widths where level repulsion fades out. Meanwhile in the complex energy plane the repulsion of eigenvalues is quadratic in accordance with the T-noninvariant character of decaying systems. In the opposite case of strong coupling with the continuum, k short-lived states are formed (k is the number of open decay channels). These states accumulate almost the whole total width, the rest of the states becoming long-lived. Such a perestroika corresponds to separation of direct processes (a nuclear analogue of Dicke coherent superradiance). At small channel number, Ericson fluctuations of the cross sections are found to be suppressed. The one-channel case is considered in detail. The joint distribution of energies and widths is obtained. The average cross sections and density of unstable states are calculated. (orig.)

Direct cortical hemodynamic mapping of somatotopy of pig nostril sensation by functional near-infrared cortical imaging (fNCI).

Science.gov (United States)

Uga, Minako; Saito, Toshiyuki; Sano, Toshifumi; Yokota, Hidenori; Oguro, Keiji; Rizki, Edmi Edison; Mizutani, Tsutomu; Katura, Takusige; Dan, Ippeita; Watanabe, Eiju

2014-05-01

Functional near-infrared spectroscopy (fNIRS) is a neuroimaging technique for the noninvasive monitoring of human brain activation states utilizing the coupling between neural activity and regional cerebral hemodynamics. Illuminators and detectors, together constituting optodes, are placed on the scalp, but due to the presence of head tissues, an inter-optode distance of more than 2.5cm is necessary to detect cortical signals. Although direct cortical monitoring with fNIRS has been pursued, a high-resolution visualization of hemodynamic changes associated with sensory, motor and cognitive neural responses directly from the cortical surface has yet to be realized. To acquire robust information on the hemodynamics of the cortex, devoid of signal complications in transcranial measurement, we devised a functional near-infrared cortical imaging (fNCI) technique. Here we demonstrate the first direct functional measurement of temporal and spatial patterns of cortical hemodynamics using the fNCI technique. For fNCI, inter-optode distance was set at 5mm, and light leakage from illuminators was prevented by a special optode holder made of a light-shielding rubber sheet. fNCI successfully detected the somatotopy of pig nostril sensation, as assessed in comparison with concurrent and sequential somatosensory-evoked potential (SEP) measurements on the same stimulation sites. Accordingly, the fNCI system realized a direct cortical hemodynamic measurement with a spatial resolution comparable to that of SEP mapping on the rostral region of the pig brain. This study provides an important initial step toward realizing functional cortical hemodynamic monitoring during neurosurgery of human brains. Copyright © 2014. Published by Elsevier Inc.

Comprehensive cognitive and cerebral hemodynamic evaluation after cranioplasty

Directory of Open Access Journals (Sweden)

Coelho F

2014-05-01

Full Text Available Fernanda Coelho,1 Arthur Maynart Oliveira,2 Wellingson Silva Paiva,2 Fabio Rios Freire,1 Vanessa Tome Calado,1 Robson Luis Amorim,2 Iuri Santana Neville,2 Almir Ferreira de Andrade,2 Edson Bor-Seng-Shu,3 Renato Anghinah,1 Manoel Jacobsen Teixeira21Neurorehabilitation Group, Division of Neurology, 2Division of Neurosurgery, 3Neurosonology and Cerebral Hemodynamics Group, University of São Paulo Medical School, São Paulo, BrazilAbstract: Decompressive craniectomy is an established procedure to lower intracranial pressure and can save patients' lives. However, this procedure is associated with delayed cognitive decline and cerebral hemodynamics complications. Studies show the benefits of cranioplasty beyond cosmetic aspects, including brain protection, and functional and cerebrovascular aspects, but a detailed description of the concrete changes following this procedure are lacking. In this paper, the authors report a patient with trephine syndrome who underwent cranioplasty; comprehensive cognitive and cerebral hemodynamic evaluations were performed prior to and following the cranioplasty. The discussion was based on a critical literature review.Keywords: cranioplasty, decompressive craniotomy, perfusion CT, traumatic brain injury, cognition, neuropsychological test

Hemodynamic effects of a novel pharmacologic stress agent, Higemine

International Nuclear Information System (INIS)

Zhang, X.L.; Liu, X.J.; Tao, Z.H.; Shi, R.F.

2002-01-01

Objective: Higenamine (dl-demethylcodaurine) (HG), which was isolated from aconitum japonicum. This study was to evaluate the hemodynamic effects of HG in animal study. Methods: We compared the hemodynamic effects of HG (0.5-4μg/min/kg) with Dobutamine (Dob) (5-30μg/min/kg) in 6 dogs: heart rate (HR), blood pressure (BP), coronary blood flow (CBF), myocardial oxygen consumption (MOC) were measured. Tolerability and safety of HG (1-500μg/mg/min) were evaluated in 8 dogs. Results: Comparison of hemodynamic effects between Dob an HG was presented. SBP: systolic blood pressure; DP: diastolic blood pressure; P<0.01; P<0.05. Diastolic BP slightly decreased, but systolic BP did not change significantly during HG infusion. There was no significant ECG abnormalities and side effects during HG infusion. Conclusion: HG might be a safe and useful pharmacologic stress agent, especially for patients with severe hypertension

Hemodynamic Change in Pulmonary Vein Stenosis after Radiofrequency Ablation: Assessment with Magnetic Resonance Angiography

Energy Technology Data Exchange (ETDEWEB)

Yun, Doyoung; Jung, Jung Im; Oh, Yong Seog; Youn, Ho Joong [Seoul St. Mary' s Hospital, College of Medicine, The Catholic University of Korea, Seoul (Korea, Republic of)

2012-11-15

We present a case of pulmonary vein (PV) stenosis after radio-frequency (RF) ablation, in which a hemodynamic change in the pulmonary artery was similar to that of congenital PV atresia on time-resolved contrast-enhanced magnetic resonance angiography (TR-MRA). A 48-year-old man underwent RF ablation due to atrial fibrillation. The patient subsequently complained of hemoptysis, dyspnea on exertion, and right chest pain. Right PV stenosis after catheter ablation was diagnosed through chest computed tomography and lung perfusion scan. Pulmonary TR-MRA revealed the pulmonary artery via systemic arterial collaterals and draining systemic collateral veins. On a velocity-encoded cine image, the flow direction of the right pulmonary artery was reversed in the diastolic phase and the left pulmonary artery demonstrated continuous forward flow throughout the cardiac cycle. These hemodynamic changes were similar to those seen in congenital unilateral PV atresia.

Brownian motion surviving in the unstable cubic potential and the role of Maxwell's demon

Science.gov (United States)

Ornigotti, Luca; Ryabov, Artem; Holubec, Viktor; Filip, Radim

2018-03-01

The trajectories of an overdamped particle in a highly unstable potential diverge so rapidly, that the variance of position grows much faster than its mean. A description of the dynamics by moments is therefore not informative. Instead, we propose and analyze local directly measurable characteristics, which overcome this limitation. We discuss the most probable particle position (position of the maximum of the probability density) and the local uncertainty in an unstable cubic potential, V (x ) ˜x3 , both in the transient regime and in the long-time limit. The maximum shifts against the acting force as a function of time and temperature. Simultaneously, the local uncertainty does not increase faster than the observable shift. In the long-time limit, the probability density naturally attains a quasistationary form. We interpret this process as a stabilization via the measurement-feedback mechanism, the Maxwell demon, which works as an entropy pump. The rules for measurement and feedback naturally arise from the basic properties of the unstable dynamics. All reported effects are inherent in any unstable system. Their detailed understanding will stimulate the development of stochastic engines and amplifiers and, later, their quantum counterparts.

Symmetry energy, unstable nuclei and neutron star crusts

Energy Technology Data Exchange (ETDEWEB)

Iida, Kei [Kochi University, Department of Natural Science, Kochi (Japan); RIKEN Nishina Center, Saitama (Japan); Oyamatsu, Kazuhiro [RIKEN Nishina Center, Saitama (Japan); Aichi Shukutoku University, Department of Human Informatics, Aichi (Japan)

2014-02-15

The phenomenological approach to inhomogeneous nuclear matter is useful to describe fundamental properties of atomic nuclei and neutron star crusts in terms of the equation of state of uniform nuclear matter. We review a series of researches that we have developed by following this approach. We start with more than 200 equations of state that are consistent with empirical masses and charge radii of stable nuclei and then apply them to describe matter radii and masses of unstable nuclei, proton elastic scattering and total reaction cross sections off unstable nuclei, and nuclei in neutron star crusts including nuclear pasta. We finally discuss the possibility of constraining the density dependence of the symmetry energy from experiments on unstable nuclei and even observations of quasi-periodic oscillations in giant flares of soft gamma-ray repeaters. (orig.)

An efficient multi-stage algorithm for full calibration of the hemodynamic model from BOLD signal responses

KAUST Repository

Zambri, Brian; Djellouli, Rabia; Laleg-Kirati, Taous-Meriem

2017-01-01

We propose a computational strategy that falls into the category of prediction/correction iterative-type approaches, for calibrating the hemodynamic model introduced by Friston et al. (2000). The proposed method is employed to estimate consecutively the values of the biophysiological system parameters and the external stimulus characteristics of the model. Numerical results corresponding to both synthetic and real functional Magnetic Resonance Imaging (fMRI) measurements for a single stimulus as well as for multiple stimuli are reported to highlight the capability of this computational methodology to fully calibrate the considered hemodynamic model. This article is protected by copyright. All rights reserved.

An efficient multi-stage algorithm for full calibration of the hemodynamic model from BOLD signal responses

KAUST Repository

Zambri, Brian

2017-02-22

We propose a computational strategy that falls into the category of prediction/correction iterative-type approaches, for calibrating the hemodynamic model introduced by Friston et al. (2000). The proposed method is employed to estimate consecutively the values of the biophysiological system parameters and the external stimulus characteristics of the model. Numerical results corresponding to both synthetic and real functional Magnetic Resonance Imaging (fMRI) measurements for a single stimulus as well as for multiple stimuli are reported to highlight the capability of this computational methodology to fully calibrate the considered hemodynamic model. This article is protected by copyright. All rights reserved.

Unstable decay and state selection

International Nuclear Information System (INIS)

McKane, Alan; Tarlie, Martin

2001-01-01

The decay of unstable states when several metastable states are available for occupation is investigated using path-integral techniques. Specifically, a method is described that enables the probabilities with which the metastable states are occupied to be calculated by finding optimal paths, and fluctuations about them, in the weak-noise limit. The method is illustrated on a system described by two coupled Langevin equations, which are found in the study of instabilities in fluid dynamics and superconductivity. The problem involves a subtle interplay between nonlinearities and noise, and a naive approximation scheme that does not take this into account is shown to be unsatisfactory. The use of optimal paths is briefly reviewed and then applied to finding the conditional probability of ending up in one of the metastable states, having begun in the unstable state. There are several aspects of the calculation that distinguish it from most others involving optimal paths: (i) the paths do not begin and end on an attractor, and moreover, the final point is to a large extent arbitrary, (ii) the interplay between the fluctuations and the leading-order contribution are at the heart of the method, and (iii) the final result involves quantities that are not exponentially small in the noise strength. This final result, which gives the probability of a particular state being selected in terms of the parameters of the dynamics, is remarkably simple and agrees well with the results of numerical simulations. The method should be applicable to similar problems in a number of other areas, such as state selection in lasers, activationless chemical reactions, and population dynamics in fluctuating environments

Hemodynamics alter arterial low-density lipoprotein metabolism

International Nuclear Information System (INIS)

Warty, V.S.; Calvo, W.J.; Berceli, S.A.; Pham, S.M.; Durham, S.J.; Tanksale, S.K.; Klein, E.C.; Herman, I.M.; Borovetz, H.S.

1989-01-01

We have investigated the role of hemodynamic factors on low-density lipoprotein transport and metabolism in the intact arterial wall. Freshly excised canine carotid blood vessels were exposed to well-defined pulsatile flow in vitro for continuous periods up to 20 hours. We chose to impose the following hemodynamic conditions on our test carotid arteries: normotension, hypertension (at physiologic flow conditions), and hypertension coupled with elevated flow of canine serum perfusate. In several experiments the effect of endothelial denudation was examined in carotid arteries exposed to normotensive pulsatile flow. A trapped ligand method was used for quantitating low-density lipoprotein uptake and metabolism in the arterial wall. The distribution of both intact and degraded low-density lipoprotein fractions was determined from measurements of radiolabelled low-density lipoprotein activity within thin radial sections of perfused arteries. Our results suggest that both hypertensive hemodynamic simulations exacerbate the uptake of low-density lipoprotein within the arterial wall (by a factor of three to nine). The percentage of low-density lipoprotein that undergoes irreversible degradation falls from 41% under normotensive conditions to below 30% when hypertensive conditions are imposed, indicating that degradative processes are not proportionally elevated with the accelerated influx. A similar pattern is observed for deendothelialized vessels

HEMODYNAMIC EFFECTS OF XENON ANESTHESIA IN CHILDREN

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M. V. Bykov

2014-01-01

Full Text Available The study was aimed at hemodynamic effects of xenon on operative interventions in children. Patients and methods: the study involved 30 5-17-year-old children – 10 (33.3% girls and 20 (66.7% boys with ASA score 1-3 admitted for surgical treatment. The children underwent endotracheal anesthesia with xenon-oxygen mixture (Xe:O2 = 60-65:30% and fentanyl (2.5‑3.5  mcg/kg per hour for the following operations: appendectomy – 10 (33.3% patients, herniotomy – 8 (26.7% patients, Ivanissevich procedure – 6 (20.0% patients, plastic surgery of posttraumatic defects of skin and soft tissues – 4 (13.3% patients, abdominal adhesiotomy – 2 (6.7% patients. Central hemodynamics was studied echocardiographically (Philips HD 11, the Netherlands using the Teichholz technique along the cephalocaudal axis (parasternal access. Results: the anesthesia was notable for hemodynamic stability during the operation: as a result, a statistically significant (p < 0.05 increase in systolic, diastolic and mean arterial pressure by 10, 18 and 17%, respectively, was observed. Conclusion: the analysis demonstrated that xenon anesthesia improves lusitropic myocardial function statistically significantly increasing cardiac output by 12% by way of increasing stroke volume by 30%. 

Diagnosis of unstable angina pectoris has declined markedly with the advent of more sensitive troponin assays.

Science.gov (United States)

D'Souza, Maria; Sarkisian, Laura; Saaby, Lotte; Poulsen, Tina S; Gerke, Oke; Larsen, Torben B; Diederichsen, Axel C P; Jangaard, Nikolaj; Diederichsen, Søren Z; Hosbond, Susanne; Hove, Jens; Thygesen, Kristian; Mickley, Hans

2015-08-01

Since the arrival of the universal definition of myocardial infarction more sensitive troponin assays have been developed. How these occurrences have influenced the proportions and clinical features of the components of acute coronary syndrome have not been studied prospectively in unselected hospital patients. During 2010 we evaluated all patients in whom cardiac troponin I had been measured at a single university hospital. The diagnosis of acute myocardial infarction (ST-elevation myocardial infarction [STEMI] or non-ST-elevation myocardial infarction [NSTEMI]) was established in cases of a rise and/or fall of cardiac troponin I together with cardiac ischemic features. Patients with unstable chest discomfort and cardiac troponin I values below the decision limit of myocardial infarction were diagnosed as having unstable angina pectoris. The definition of acute coronary syndrome included unstable angina pectoris, NSTEMI, and STEMI. Mortality data were obtained from the Danish Civil Personal Registration System. Of 3762 consecutive patients, 516 had acute coronary syndrome. Unstable angina pectoris was present in 7%, NSTEMI in 67%, and STEMI in 26%. The NSTEMI patients were older, more frequently women, and had more comorbidities than patients with unstable angina pectoris and STEMI. At median follow-up of 3.2 years 195 patients had died: 14% of unstable angina pectoris, 45% of NSTEMI, and 25% of STEMI patients. Age-adjusted log-rank statistics revealed differences in mortality: NSTEMI vs unstable angina pectoris (P = .0091) and NSTEMI vs STEMI (P = .0045). The application of the universal definition together with the use of a contemporary troponin assay seems to have reduced the proportion of patients with unstable angina pectoris to the benefit of patients with NSTEMI. Despite this, NSTEMI patients have a sustained higher mortality than patients with STEMI. Copyright © 2015 Elsevier Inc. All rights reserved.

RENAL AND SYSTEMIC HEMODYNAMIC-EFFECTS OF IBOPAMINE IN PATIENTS WITH MILD-TO-MODERATE CONGESTIVE-HEART-FAILURE

NARCIS (Netherlands)

LIEVERSE, AG; VANVELDHUISEN, DJ; SMIT, AJ; ZIJLSTRA, JG; MEIJER, S; REITSMA, WD; LIE, KI; GIRBES, ARJ

To study the hemodynamic and renal effects of the orally (p.o.) active dopamine (DA) agonist ibopamine, we examined 10 patients with mild to moderate congestive heart failure (CHF), who were stable while treated with digoxin and diuretics. All patients were in New York Heart Association (NYHA)

Resting-state hemodynamics are spatiotemporally coupled to synchronized and symmetric neural activity in excitatory neurons

Science.gov (United States)

Ma, Ying; Shaik, Mohammed A.; Kozberg, Mariel G.; Portes, Jacob P.; Timerman, Dmitriy

2016-01-01

Brain hemodynamics serve as a proxy for neural activity in a range of noninvasive neuroimaging techniques including functional magnetic resonance imaging (fMRI). In resting-state fMRI, hemodynamic fluctuations have been found to exhibit patterns of bilateral synchrony, with correlated regions inferred to have functional connectivity. However, the relationship between resting-state hemodynamics and underlying neural activity has not been well established, making the neural underpinnings of functional connectivity networks unclear. In this study, neural activity and hemodynamics were recorded simultaneously over the bilateral cortex of awake and anesthetized Thy1-GCaMP mice using wide-field optical mapping. Neural activity was visualized via selective expression of the calcium-sensitive fluorophore GCaMP in layer 2/3 and 5 excitatory neurons. Characteristic patterns of resting-state hemodynamics were accompanied by more rapidly changing bilateral patterns of resting-state neural activity. Spatiotemporal hemodynamics could be modeled by convolving this neural activity with hemodynamic response functions derived through both deconvolution and gamma-variate fitting. Simultaneous imaging and electrophysiology confirmed that Thy1-GCaMP signals are well-predicted by multiunit activity. Neurovascular coupling between resting-state neural activity and hemodynamics was robust and fast in awake animals, whereas coupling in urethane-anesthetized animals was slower, and in some cases included lower-frequency (resting-state hemodynamics in the awake and anesthetized brain are coupled to underlying patterns of excitatory neural activity. The patterns of bilaterally-symmetric spontaneous neural activity revealed by wide-field Thy1-GCaMP imaging may depict the neural foundation of functional connectivity networks detected in resting-state fMRI. PMID:27974609

Central Hemodynamics and Arterial Stiffness in Systemic Sclerosis.

Science.gov (United States)

Bartoloni, Elena; Pucci, Giacomo; Cannarile, Francesca; Battista, Francesca; Alunno, Alessia; Giuliani, Marco; Cafaro, Giacomo; Gerli, Roberto; Schillaci, Giuseppe

2016-12-01

Although microvascular disease is a hallmark of systemic sclerosis (SSc), a higher prevalence of macrovascular disease and a poorer related prognosis have been reported in SSc than in the general population. The simultaneous assessment of prognostically relevant functional properties of larger and smaller arteries, and their effects on central hemodynamics, has never been performed in SSc using the state-of-the-art techniques. Thirty-four women with SSc (aged 61±15 years, disease duration 17±12 years, and blood pressure 123/70±18/11 mm Hg) and 34 healthy women individually matched by age and mean arterial pressure underwent the determination of carotid-femoral (aortic) and carotid-radial (upper limb) pulse wave velocity (a direct measure of arterial stiffness), aortic augmentation (a measure of the contribution of reflected wave to central pulse pressure), and aortobrachial pulse pressure amplification (brachial/aortic pulse pressure) through applanation tonometry (SphygmoCor). Patients and controls did not differ by carotid-femoral or carotid-radial pulse wave velocity. Aortic augmentation index corrected for a heart rate of 75 bpm (AIx@75) was higher in women with SSc (30.9±16% versus 22.2±12%; P=0.012). Patients also had a lower aortobrachial amplification of pulse pressure (1.22±0.18 versus 1.33±0.25; P=0.041). SSc was an independent predictor of AIx@75 (direct) and pulse pressure amplification (inverse). Among patients, age, mean arterial pressure, and C-reactive protein independently predicted carotid-femoral pulse wave velocity. Age and mean arterial pressure were the only predictors of AIx@75. Women with SSc have increased aortic augmentation and decreased pulse pressure amplification (both measures of the contribution of reflected wave to central waveform) but no changes in aortic or upper limb arterial stiffness. Microvascular involvement occurs earlier than large artery stiffening in SSc. © 2016 American Heart Association, Inc.

ECG Markers of Hemodynamic Improvement in Patients with Pulmonary Hypertension

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Marcin Waligóra

2018-01-01

Full Text Available Introduction. Several diagnostic tests have been recommended for risk assessment in pulmonary hypertension (PH, but the role of electrocardiography (ECG in monitoring of PH patients has not been yet established. Therefore the aim of the study was to evaluate which ECG patterns characteristic for pulmonary hypertension can predict hemodynamic improvement in patients treated with targeted therapies. Methods. Consecutive patients with pulmonary arterial hypertension (PAH or chronic thromboembolic pulmonary hypertension (CTEPH were eligible to be included if they had had performed two consecutive right heart catheterization (RHC procedures before and after starting of targeted therapies. Patients were followed up from June 2009 to July 2017. ECG patterns of right ventricular hypertrophy according to American College of Cardiology Foundation were assessed. Results. We enrolled 80 patients with PAH and 11 patients with inoperable CTEPH. The follow-up RHC was performed within 12.6±10.0 months after starting therapy. Based on median change of pulmonary vascular resistance, we divided our patients into two subgroups: with and without significant hemodynamic improvement. RV1, max⁡RV1,2 + max⁡SI,aVL-SV1, and PII improved along with the improvement of hemodynamic parameters including PVR. They predicted hemodynamic improvement with similarly good accuracy as shown in ROC analysis: RV1 (AUC: 0.75; 95% CI: 0.63–0.84, PII (AUC: 0.67, 95% CI: 0.56–0.77, and max⁡RV1,2+max⁡SI,aVL-SV1 (0.73; 95% CI: 0.63–0.82. In Cox regression only change in RV1 remained significant mortality predictor (HR: 1.12, 95% CI: 1.01–1.24. Conclusion. Electrocardiogram may be useful in predicting hemodynamic effects of targeted therapy in precapillary pulmonary hypertension. Decrease of RV1, max⁡RV1,2+max⁡SI,aVL-SV1, and PII corresponds with hemodynamic improvement after treatment. Of these changes a decrease of R wave amplitude in V1 is associated with better

Paradoxes of unstable electron

International Nuclear Information System (INIS)

Okun, L.B.; Zeldovich, Ya.B.

1978-01-01

The hypothesis that electron is unstable - when it is consistent with the vanishing mass of the photon- leads to a number of paradoxical statements. The lifetime of the electron is determined by emission of a huge number of longitudinal photons and exponentially depends on the amount of emitted energy. This suggests to discuss searches for charge nonconservation in experiments with high energy particles

Percutaneous artery embolization of bleeding rectus sheath hematomas in hemodynamically unstable patients: Outcomes of 43 patients in a tertiary referral hospital

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Alberto Cereda

2017-11-01

Full Text Available Rectus sheath hematoma (RSH is an uncommon cause of abdominal pain that can lead to life-threatening bleeding, particularly in elderly patients receiving anticoagulation therapy. Type III RSHs, based on computer tomography (CT evaluation, is characterized by active bleeding with intramuscular or intraperitoneal extension and hemodynamic instability. Medical contemporary knowledge of this condition is contentious and overall 20% of acute mortality has been reported. The purpose of this study was to retrospectively review our experience and outcomes in the management of RSHs treated with percutaneous arterial embolization of the epigastric vessels. We retrospectively analyzed 43 patients with RSH type III, submitted to percutaneous epigastric artery embolization from 2007 to 2015. Percutaneous arterial embolization was feasible and successful in patients with a high burden of comorbidities and receiving anticoagulation therapy. There was no acute mortality and a late mortality at 3 months of 9.1% (4/43 was not directly related to RSHs or arterial embolization. Patients with late mortality had lower ejection fraction, prolonged PTT, greater RDW and warfarin in overlapping with low-molecular-weight heparins. Transcatheter arterial embolization of the epigastric vessels was safe, feasible and effective in stopping the bleeding. Despite anti-platelets/anti-coagulation therapy and a high burden of comorbidities, there was no acute mortality related to RSH.

Ocular hemodynamics and glaucoma: the role of mathematical modeling.

Science.gov (United States)

Harris, Alon; Guidoboni, Giovanna; Arciero, Julia C; Amireskandari, Annahita; Tobe, Leslie A; Siesky, Brent A

2013-01-01

To discuss the role of mathematical modeling in studying ocular hemodynamics, with a focus on glaucoma. We reviewed recent literature on glaucoma, ocular blood flow, autoregulation, the optic nerve head, and the use of mathematical modeling in ocular circulation. Many studies suggest that alterations in ocular hemodynamics play a significant role in the development, progression, and incidence of glaucoma. Although there is currently a limited number of studies involving mathematical modeling of ocular blood flow, regulation, and diseases (such as glaucoma), preliminary modeling work shows the potential of mathematical models to elucidate the mechanisms that contribute most significantly to glaucoma progression. Mathematical modeling is a useful tool when used synergistically with clinical and laboratory data in the study of ocular blood flow and glaucoma. The development of models to investigate the relationship between ocular hemodynamic alterations and glaucoma progression will provide a unique and useful method for studying the pathophysiology of glaucoma.

Signatures of unstable semiclassical trajectories in tunneling

International Nuclear Information System (INIS)

Levkov, D G; Panin, A G; Sibiryakov, S M

2009-01-01

It was found recently that processes of multidimensional tunneling are generally described at high energies by unstable semiclassical trajectories. We study two observational signatures related to the instability of trajectories. First, we find an additional power-law dependence of the tunneling probability on the semiclassical parameter as compared to the standard case of potential tunneling. The second signature is a substantial widening of the probability distribution over final-state quantum numbers. These effects are studied using a modified semiclassical technique which incorporates stabilization of the tunneling trajectories. The technique is derived from first principles. We obtain expressions for the inclusive and exclusive tunneling probabilities in the case of unstable semiclassical trajectories. We also investigate the 'phase transition' between the cases of stable and unstable trajectories across certain 'critical' values of energy. Finally, we derive the relation between the semiclassical probabilities of tunneling from the low-lying and highly excited initial states. This puts on firm ground a conjecture made previously in the semiclassical description of collision-induced tunneling in field theory

Robustness of unstable attractors in arbitrarily sized pulse-coupled networks with delay

NARCIS (Netherlands)

Broer, Hendrik; Efstathiou, Konstantinos; Subramanian, Easwar

We consider arbitrarily large networks of pulse-coupled oscillators with non-zero delay where the coupling is given by the Mirollo-Strogatz function. We prove that such systems have unstable attractors (saddle periodic orbits whose stable set has non-empty interior) in an open parameter region for

Computational medical imaging and hemodynamics framework for functional analysis and assessment of cardiovascular structures.

Science.gov (United States)

Wong, Kelvin K L; Wang, Defeng; Ko, Jacky K L; Mazumdar, Jagannath; Le, Thu-Thao; Ghista, Dhanjoo

2017-03-21

Cardiac dysfunction constitutes common cardiovascular health issues in the society, and has been an investigation topic of strong focus by researchers in the medical imaging community. Diagnostic modalities based on echocardiography, magnetic resonance imaging, chest radiography and computed tomography are common techniques that provide cardiovascular structural information to diagnose heart defects. However, functional information of cardiovascular flow, which can in fact be used to support the diagnosis of many cardiovascular diseases with a myriad of hemodynamics performance indicators, remains unexplored to its full potential. Some of these indicators constitute important cardiac functional parameters affecting the cardiovascular abnormalities. With the advancement of computer technology that facilitates high speed computational fluid dynamics, the realization of a support diagnostic platform of hemodynamics quantification and analysis can be achieved. This article reviews the state-of-the-art medical imaging and high fidelity multi-physics computational analyses that together enable reconstruction of cardiovascular structures and hemodynamic flow patterns within them, such as of the left ventricle (LV) and carotid bifurcations. The combined medical imaging and hemodynamic analysis enables us to study the mechanisms of cardiovascular disease-causing dysfunctions, such as how (1) cardiomyopathy causes left ventricular remodeling and loss of contractility leading to heart failure, and (2) modeling of LV construction and simulation of intra-LV hemodynamics can enable us to determine the optimum procedure of surgical ventriculation to restore its contractility and health This combined medical imaging and hemodynamics framework can potentially extend medical knowledge of cardiovascular defects and associated hemodynamic behavior and their surgical restoration, by means of an integrated medical image diagnostics and hemodynamic performance analysis framework.

Comparison of the hemodynamic effects of etomidate between hypertensive and normotensive patients

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Hayrettin Daşkaya

2014-06-01

Full Text Available Objective: Comparison of the hemodynamic effect of ethomidate induction in normotensive and hypertensive patients. Methods: Forty ASA 1-2 patients were included. After informed consent were obtained, patients were divided into two group; Group H: Hypertensive patients, Group N: Normotensive patients. Fentanile and midazolam were administrated for premedication. Anesthesia induction was performed by etomidate 0.3 mg/kg and rocuronium 0.6 mg/kg. Arterial pressures and heart rates were measured at certain intervals: control, pre-intubation and 1, 3 and 5 min post-intubation. Myoclonic movements and hemodynamic parameters were noted by an anesthetist who was masked to the groups. Results: Hemodynamic parameters were higher in hypertensive patients but were in clinically tolerable limits. Conclusion: No hemodynamic instability was observed in anesthesia induction with ethomidate in neither hypertensive nor normotensive patients. J Clin Exp Invest 2014; 5 (2: 164-168

Unstable Pore-Water Flow in Intertidal Wetlands

Science.gov (United States)

Barry, D. A.; Shen, C.; Li, L.

2014-12-01

Salt marshes are important intertidal wetlands strongly influenced by interactions between surface water and groundwater. Bordered by coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur over vastly different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil condition, particularly aeration, which influences the marsh plant growth. Numerous studies have been carried out to examine the pore-water flow process in the marsh soil driven by tides, focusing on stable flow with the assumption of homogeneity in soil and fluid properties. This assumption, however, is questionable given the actual inhomogeneous conditions in the field. For example, the salinity of surface water in the tidal creek varies temporally and spatially due to the influence of rainfall and evapotranspiration as well as the freshwater input from upland areas to the estuary, creating density gradients across the marsh surface and within the marsh soil. Many marshes possess soil stratigraphy with low-permeability mud typically overlying high-permeability sandy deposits. Macropores such as crab burrows are commonly distributed in salt marsh sediments. All these conditions are prone to the development of non-uniform, unstable preferential pore-water flow in the marsh soil, for example, funnelling and fingering. Here we present results from laboratory experiments and numerical simulations to explore such unstable flow. In particular, the analysis aims to address how the unstable flow modifies patterns of local pore-water movement and solute transport, as well as the overall exchange between the marsh soil and

Central Hemodynamic Features in Elderly Patients During General Anesthesia with Sevoflurane

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O.I. Petrov

2011-01-01

Full Text Available Objective: to reduce the number of perioperative cardiovascular events in elderly patients during traditional cholecystectomy, by using anesthesia based on sevoflurane (SF and fentanyl (FL. Subjects and methods. Forty-eight patients aged 60 to 75 years, who were divided into 2 groups, operated on by a classical surgical technique for chronic calculous cholecystitis in the presence of concomitant coronary heart disease and essential hypertension, and had grade 3 surgical risk according to the classification of the Moscow Research Society of Anesthesiologists and Reanimatologists, were examined. Premedicaton was routine. The induction of anesthesia was as follows: intravenous propofol (PF (1.8±0.2 mg/kg and FL (2.2±0.4 mg/kg in Groups 1 and 2. General anesthesia (GA was maintained by SF (1.1±0.2 MAC and FL (2.4±0.4 jBg/kg/hr in Group 1 (n=25 and by PF (2.0—4.0 mg/kg/hr and FL (3.5±0.7 ^Bg/kg/hr in Group 2 (n=23. In both groups, mechanical ventilation was as follows: N2O:O2 = 2:1; air flow, 6 l/min. Myoplegia was rocuronium bromide (RB (0.075—0.1 mg/kg in Group 1 and RB (0.15 mg/kg in Group 2. Hemodynamics was studied during 5 stages of surgery. Results. Central hemodynamics (CH was rather stable in patients after GA with SF. Significant CH changes were noted only during the traumatic stage of surgery, which were less pronounced than those in patients following GA with PF. CH parameters returned gradually to the baseline values at the end of surgery and virtually to the background values after tracheal extubation. The patients under GA with PF showed significant CH changes at all stages of the study. Conclusion. Analysis of the systemic hemodynamic changes induced by the use of SF and PF suggests that GA with SF in elderly patients is more preferable than that in those with PF. Key words: sevoflurane, hemodynamics, elderly.

Extension of a chaos control method to unstable trajectories on infinite- or finite-time intervals: Experimental verification

International Nuclear Information System (INIS)

Yagasaki, Kazuyuki

2007-01-01

In experiments for single and coupled pendula, we demonstrate the effectiveness of a new control method based on dynamical systems theory for stabilizing unstable aperiodic trajectories defined on infinite- or finite-time intervals. The basic idea of the method is similar to that of the OGY method, which is a well-known, chaos control method. Extended concepts of the stable and unstable manifolds of hyperbolic trajectories are used here

Heteroclinic cycles between unstable attractors

NARCIS (Netherlands)

Broer, Henk; Efstathiou, Konstantinos; Subramanian, Easwar

We consider networks of pulse coupled linear oscillators with non-zero delay where the coupling between the oscillators is given by the Mirollo-Strogatz function. We prove the existence of heteroclinic cycles between unstable attractors for a network of four oscillators and for an open set of

Methylene Blue Is Effective to Reverse Refractory Hemodynamic Instability due to Dimethoate Poisoning

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Nick Youssefi

2015-09-01

Conclusion:MB treatment was effective to reverse hypotension and restore hemodynamic instability caused by dimethoate poisoning. This index case may pave way to further investigation of MB therapy for OP-induced hemodynamic instabilities.

Soleus and lateral gastrocnemius H-reflexes during standing with unstable footwear.

Science.gov (United States)

Friesenbichler, Bernd; Lepers, Romuald; Maffiuletti, Nicola A

2015-05-01

Unstable footwear has been shown to increase lower extremity muscle activity, but the reflex response to perturbations induced by this intervention is unknown. Twenty healthy subjects stood in stable and unstable footwear conditions (presented randomly) while H-reflex amplitude and background muscle activity were measured in the soleus and lateral gastrocnemius (LG) muscles. Wearing unstable footwear resulted in larger H-reflexes (normalized to the maximal M-wave) for the LG (+12%; P = 0.025), but not for the soleus (+4%; P > 0.05). Background activity of both muscles was significantly higher in the unstable condition. The H-reflex facilitation observed with unstable footwear was unexpected, as challenging postural conditions usually result in reflex depression. Increased muscle activity, decreased presynaptic inhibition, and/or more forward postural position may have (over-)compensated the expected reflex depression. Differences between LG and soleus H-reflex modulation may be due to diverging motor unit recruitment thresholds. © 2015 Wiley Periodicals, Inc.

Diastolic pressure underestimates age-related hemodynamic impairment.

Science.gov (United States)

Galarza, C R; Alfie, J; Waisman, G D; Mayorga, L M; Cámera, L A; del Río, M; Vasvari, F; Limansky, R; Farías, J; Tessler, J; Cámera, M I

1997-10-01

It has been hypothesized that as large arteries become more rigid with age, the pattern of hypertension changes from diastolic to systolic. Thus, diastolic blood pressure (DBP) may lose its ability to reflect the increase in vascular resistance with age. To assess this, we studied the age-related changes in blood pressure pattern and its steady-state and pulsatile determinants. We performed an epidemiological analysis based on a national survey of 10,462 subjects from Argentina. A hemodynamic analysis (impedance cardiography) was then carried out in 636 consecutive hypertensive patients (age, 25 to 74 years). Whereas the rate of increment in the prevalence of mild to moderate hypertension (MMH) reached a plateau after the sixth decade, isolated and borderline systolic forms of hypertension began a steep and sustained rise. Among patients with MMH, DBP remained stable from the third to the seventh decade, whereas SBP maintained a sustained increase. Despite similar DBP, the systemic vascular resistance index increased 47% (P<.01) and the cardiac index decreased 27% (P<.01), whereas the ratio of stroke volume to pulse pressure, an index of arterial compliance, decreased 45% (P<.01). However, there were no significant differences between older patients with MMH and those with isolated systolic hypertension in the level of SBP, vascular resistance, stroke volume, and cardiac index. Compared with age-matched normotensive control subjects, the ratio of stroke volume to pulse pressure was much more reduced in isolated systolic hypertension (48%) than in MMH (30%). In summary, the present study, carried out in a large sample of hypertensive subjects with a wide age range, showed a simultaneous impairment in vascular resistance and arterial compliance associated with aging in different patterns of hypertension. The magnitude of these changes, with opposite effects on DBP but additive effects on SBP, suggests that a hemodynamic mechanism could determine the transition in the

Relationship Between Serum Uric Acid Levels and Intrarenal Hemodynamic Parameters

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Hideki Uedono

2015-06-01

Full Text Available Background/Aims: Hyperuricemia has been reported to affect renal hemodynamics in rat models. We evaluate the relationship between serum uric acid and intrarenal hemodynamic parameters in humans, utilizing the plasma clearance of para-aminohippurate (CPAH and inulin (Cin. Methods: Renal and glomerular hemodynamics were assessed by simultaneous measurement of CPAH and Cin in 58 subjects. Of these, 19 subjects were planned to provide a kidney for transplantation; 26 had diabetes without proteinuria; and 13 had mild proteinuria. Renal and glomerular hemodynamics were calculated using Gomez`s formulae. Results: Cin was more than 60 ml/min/1.73m2 in all subjects. Serum uric acid levels correlated significantly with vascular resistance at the afferent arteriole (Ra (r = 0.354, p = 0.006 but not with that of the efferent arteriole (Re. Serum uric acid levels (β = 0.581, p = a after adjustment for several confounders (R2 = 0.518, p = Conclusions: These findings suggest, for the first time in humans, that higher serum uric acid levels are associated significantly with Ra in subjects with Cin > 60 ml/min/1.73m2. The increase in Ra in subjects with higher uric acid levels may be related to dysfunction of glomerular perfusion.

Novel use of a noninvasive hemodynamic monitor in a personalized, active learning simulation.

Science.gov (United States)

Zoller, Jonathan K; He, Jianghua; Ballew, Angela T; Orr, Walter N; Flynn, Brigid C

2017-06-01

The present study furthered the concept of simulation-based medical education by applying a personalized active learning component. We tested this novel approach utilizing a noninvasive hemodynamic monitor with the capability to measure and display in real time numerous hemodynamic parameters in the exercising participant. Changes in medical knowledge concerning physiology were examined with a pre-and posttest. Simply by observation of one's own hemodynamic variables, the understanding of complex physiological concepts was significantly enhanced. Copyright © 2017 the American Physiological Society.

Invasive and noninvasive hemodynamic monitoring of patients with cerebrovascular accidents.

Science.gov (United States)

Velmahos, G C; Wo, C C; Demetriades, D; Bishop, M H; Shoemaker, W C

1998-01-01

Seventeen patients with hemodynamic instability from acute cerebrovascular accidents were evaluated shortly after arrival at the emergency department of a university-run county hospital with both invasive Swan-Ganz pulmonary artery catheter placement and a new, noninvasive, thoracic electrical bioimpedance device. Values were recorded and temporal patterns of survivors and nonsurvivors were described. Cardiac indices obtained simultaneously by the 2 techniques were compared. Of the 17 patients, 11 (65%) died. Survivors had higher values than nonsurvivors for mean arterial pressure, cardiac index, and oxygen saturation, delivery, and consumption at comparable times. Cardiac index values, as measured by invasive and noninvasive methods, were correlated. We concluded that hemodynamic monitoring in an acute care setting may recognize temporal circulatory patterns associated with outcome. Noninvasive electrical bioimpedance technology offers a new method for early hemodynamic evaluation. Further research in this area is warranted. PMID:9682626

Dataset for: An efficient multi-stage algorithm for full calibration of the hemodynamic model from BOLD signal responses

KAUST Repository

Djellouli, Rabia

2017-01-01

We propose a computational strategy that falls into the category of prediction/correction iterative-type approaches, for calibrating the hemodynamic model introduced by Friston et al. (2000). The proposed method is employed to estimate consecutively the values of the biophysiological system parameters and the external stimulus characteristics of the model. Numerical results corresponding to both synthetic and real functional Magnetic Resonance Imaging (fMRI) measurements for a single stimulus as well as for multiple stimuli are reported to highlight the capability of this computational methodology to fully calibrate the considered hemodynamic model.

[Metabolic and hemodynamic effects of the growth hormone system - insulin-like growth factor].

Science.gov (United States)

Manhylova, T A; Gafarova, N H

2015-01-01

Significant congenital deficiency of growth factor (GF) results in pituitary nanism (dwarfism) and its substantial excess is accompanied by the development of gigantism or acromegaly. Its impact on the growth of the whole body or its individual parts is impossible without affecting metabolic processes and hemodynamic parameters. A number of investigations have proven that GF has a direct lipolytic effect: adequate replacement therapy for pituitary nanism gives rise to a reduction in fat depots. Since the concentration of GF is lower in obesity, Whether it may be used to treat this abnormality is considered.

Direct numerical simulation of stable and unstable turbulent thermal boundary layers

International Nuclear Information System (INIS)

Hattori, Hirofumi; Houra, Tomoya; Nagano, Yasutaka

2007-01-01

This paper presents direct numerical simulations (DNS) of stable and unstable turbulent thermal boundary layers. Since a buoyancy-affected boundary layer is often encountered in an urban environmental space where stable and unstable stratifications exist, exploring a buoyancy-affected boundary layer is very important to know the transport phenomena of the flow in an urban space. Although actual observation may qualitatively provide the characteristics of these flows, the relevant quantitative turbulent quantities are very difficult to measure. Thus, in order to quantitatively investigate a buoyancy-affected boundary layer in detail, we have here carried out for the first time time- and space-developing DNS of slightly stable and unstable turbulent thermal boundary layers. The DNS results show the quantitative turbulent statistics and structures of stable and unstable thermal boundary layers, in which the characteristic transport phenomena of thermally stratified boundary layers are demonstrated by indicating the budgets of turbulent shear stress and turbulent heat flux. Even though the input of buoyant force is not large, the influence of buoyancy is clearly revealed in both stable and unstable turbulent boundary layers. In particular, it is found that both stable and unstable thermal stratifications caused by the weak buoyant force remarkably alter the structure of near-wall turbulence

Heteroclinic cycles between unstable attractors

International Nuclear Information System (INIS)

Broer, Henk; Efstathiou, Konstantinos; Subramanian, Easwar

2008-01-01

We consider networks of pulse coupled linear oscillators with non-zero delay where the coupling between the oscillators is given by the Mirollo–Strogatz function. We prove the existence of heteroclinic cycles between unstable attractors for a network of four oscillators and for an open set of parameter values

Cerebral hemodynamic and metabolic changes in fulminant hepatic failure

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Fernando Mendes Paschoal Junior

Full Text Available ABSTRACT Intracranial hypertension and brain swelling are a major cause of morbidity and mortality of patients suffering from fulminant hepatic failure (FHF. The pathogenesis of these complications has been investigated in man, in experimental models and in isolated cell systems. Currently, the mechanism underlying cerebral edema and intracranial hypertension in the presence of FHF is multi-factorial in etiology and only partially understood. The aim of this paper is to review the pathophysiology of cerebral hemodynamic and metabolism changes in FHF in order to improve understanding of intracranial dynamics complication in FHF.

Hemodynamic effects of sodium bicarbonate administration.

Science.gov (United States)

Katheria, A C; Brown, M K; Hassan, K; Poeltler, D M; Patel, D A; Brown, V K; Sauberan, J B

2017-05-01

To describe the hemodynamic changes that occur with sodium bicarbonate (NaHCO 3 ) administration in premature neonates. This retrospective study included premature neonates 23 to 31+6 weeks of gestational age who underwent continuous cardiac and cerebral monitoring as participants in prospective trials at our institution, and who received NaHCO 3 infused over 30 min in the first 24 h of life. Blood pressure (BP), heart rate, cardiac output (CO), SpO 2 and cerebral oximetry (StO 2 ) were captured every 2 s. A baseline was established for all continuous data and averaged over the 10 min before NaHCO 3 administration. Baseline was compared with measurements over 10 min epochs until 80 min after administration. Arterial blood gases before and within 1 h of administration were also compared. Significance was set at P<0.05. A total of 36 subjects received NaHCO 3 (1.3±0.3 mEq kg -1 ) in the first 24 h (14±8.5 h) of life. NaHCO 3 administration increased pH (7.23 vs 7.28, P<0.01) and decreased base deficit (-8.9 vs -6.8, P<0.01) and PaCO 2 (45 vs 43 mm Hg, P<0.05). There was a transient but significant (P<0.05) decrease in systemic BP coinciding with an increase in cerebral oxygenation without an increase in oxygen extraction. CO did not change. Early postnatal NaHCO 3 administration does not acutely improve CO but does cause transient fluctuations in cerebral and cardiovascular hemodynamics in extremely premature infants.

Significance of Tc-99m pyrophosphate accumulation in unstable angina

International Nuclear Information System (INIS)

Tange, Shoichi; Kondo, Chisato; Ohta, Yoshiko; Kusakabe, Kiyoko; Shigeta, Akiko; Uchida, Tatsuro; Sumiyoshi, Tetsuya; Kaneko, Noboru; Hosoda, Saichi

1993-01-01

Tc-99m pyrophosphate (PYP) and Tl-201 simultaneous dual energy single photon emission computed tomography (SPECT) were performed in 33 patients with clinically unstable angina. According to the presence or absence of PYP accumulation in the myocardium, the patients were classified as PYP (+) group (n=22) and PYP (-) group (n=11). Clinical features, types of unstable angina, ECG changes, and serial creatine kinase (CK) data were compared in the two groups. The 'new angina at rest' type of unstable angina was more significantly common in the PYP (+) group (16/22) than the PYP (-) group (2/11). The remaining 6 patients in the PYP (+) group and 2 patients in the PYP (-) group had 'angina of effort with changing pattern'. There was a significant difference in the occurrence of ST elevation and ST depression between the group: 59% in the PYP (+) group vs. 18% in the PYP (-) group for ST elevation and 23% in the PYP (+) group vs. 64% in the PYP (-) group for ST depression. The PYP (+) group showed significant improvement in ejection fraction in the stable state (57±12%) as compared with the unstable state (62±11%), although there was no difference between the stable and unstable state in the PYP (-) group. Although wall motion abnormality index (WMI) was poorer in the PYP (+) group than the PYP (-) group, it improved to the same degree as the PYP (-) group one month later. These data suggest that the area showing PYP (+) may reflect stunned myocardium and that Tc-99m PYP accumulation may correlate with clinical features of unstable angina. (N.K.)

Robustness of unstable attractors in arbitrarily sized pulse-coupled networks with delay

International Nuclear Information System (INIS)

Broer, Henk; Efstathiou, Konstantinos; Subramanian, Easwar

2008-01-01

We consider arbitrarily large networks of pulse-coupled oscillators with non-zero delay where the coupling is given by the Mirollo–Strogatz function. We prove that such systems have unstable attractors (saddle periodic orbits whose stable set has non-empty interior) in an open parameter region for three or more oscillators. The evolution operator of the system can be discontinuous and we propose an improved model with continuous evolution operator

From stable to unstable anomaly-induced inflation

Science.gov (United States)

Netto, Tibério de Paula; Pelinson, Ana M.; Shapiro, Ilya L.; Starobinsky, Alexei A.

2016-10-01

Quantum effects derived through conformal anomaly lead to an inflationary model that can be either stable or unstable. The unstable version requires a large dimensionless coefficient of about 5× {10}^8 in front of the {R}^2 term that results in the inflationary regime in the R+{R}^2 ("Starobinsky") model being a generic intermediate attractor. In this case the non-local terms in the effective action are practically irrelevant, and there is a `graceful exit' to a low curvature matter-like dominated stage driven by high-frequency oscillations of R - scalarons, which later decay to pairs of all particles and antiparticles, with the amount of primordial scalar (density) perturbations required by observations. The stable version is a genuine generic attractor, so there is no exit from it. We discuss a possible transition from stable to unstable phases of inflation. It is shown that this transition is automatic if the sharp cut-off approximation is assumed for quantum corrections in the period of transition. Furthermore, we describe two different quantum mechanisms that may provide a required large {R}^2-term in the transition period.

From stable to unstable anomaly-induced inflation

Energy Technology Data Exchange (ETDEWEB)

Paula Netto, Tiberio de [Universidade Federal de Juiz de Fora, Departamento de Fisica, ICE, Juiz de Fora, MG (Brazil); Pelinson, Ana M. [Universidade Federal de Santa Catarina, Departamento de Fisica, CFM, Bairro da Trindade, Florianopolis, SC (Brazil); Shapiro, Ilya L. [Universidade Federal de Juiz de Fora, Departamento de Fisica, ICE, Juiz de Fora, MG (Brazil); Tomsk State Pedagogical University and Tomsk State University, Tomsk (Russian Federation); Starobinsky, Alexei A. [L.D. Landau Institute for Theoretical Physics RAS, Moscow (Russian Federation); Utrecht University, Department of Physics and Astronomy, Institute for Theoretical Physics, Utrecht (Netherlands)

2016-10-15

Quantum effects derived through conformal anomaly lead to an inflationary model that can be either stable or unstable. The unstable version requires a large dimensionless coefficient of about 5 x 10{sup 8} in front of the R{sup 2} term that results in the inflationary regime in the R+R{sup 2} (''Starobinsky'') model being a generic intermediate attractor. In this case the non-local terms in the effective action are practically irrelevant, and there is a 'graceful exit' to a low curvature matter-like dominated stage driven by high-frequency oscillations of R - scalarons, which later decay to pairs of all particles and antiparticles, with the amount of primordial scalar (density) perturbations required by observations. The stable version is a genuine generic attractor, so there is no exit from it. We discuss a possible transition from stable to unstable phases of inflation. It is shown that this transition is automatic if the sharp cut-off approximation is assumed for quantum corrections in the period of transition. Furthermore, we describe two different quantum mechanisms that may provide a required large R{sup 2}-term in the transition period. (orig.)

Cerebral hematocrit decreases with hemodynamic compromise in carotid artery occlusion: a PET study.

Science.gov (United States)

Yamauchi, H; Fukuyama, H; Nagahama, Y; Katsumi, Y; Okazawa, H

1998-01-01

This study investigated whether in patients with internal carotid artery occlusion the regional cerebral hematocrit correlates with cerebral hemodynamics or metabolic state and, if so, how the regional cerebral hematocrit changes in the hemodynamically compromised region. We used positron emission tomography to study seven patients with unilateral internal carotid artery occlusion and no cortical infarction in the chronic stage. The distributions of red blood cell and plasma volumes were assessed using oxygen-15-labeled carbon monoxide and copper-62-labeled human serum albumin-dithiosemicarbazone tracers, respectively. The calculated hematocrit value was compared with the hemodynamic and metabolic parameters measured with the oxygen-15 steady-state technique. In the cerebral cortex, the value of the cerebral hematocrit varied but was correlated with the hemodynamic and metabolic status. Stepwise regression analysis revealed that the large vessel hematocrit, the cerebral metabolic rate of oxygen, and the cerebral blood flow or the oxygen extraction fraction accounted for a significant proportion of variance of the cerebral hematocrit. The oxygen extraction fraction and the cerebral metabolic rate of oxygen negatively correlated with the cerebral hematocrit, whereas the cerebral blood flow correlated positively: patients with reduced blood supply relative to metabolic demand (decreased blood flow with increased oxygen extraction fraction) showed low hematocrit values. In carotid artery occlusion in the chronic stage, regional cerebral hematocrit may vary according to cerebral hemodynamics and metabolic status. Regional cerebral hematocrit may decrease with hemodynamic compromise unless oxygen metabolism concomitantly decreases.

The role of hemodynamics in the development of the outflow tract of the heart

NARCIS (Netherlands)

Loots, Erwin; Hillen, Berend; Veldman, Arthur E.P.

The question whether, and if so to what extent, hemodynamic forces and mechanical stimuli do modulate the morphogenesis of the vascular system is a century-old problem. It is important especially in the outflow tract where a spiraling septum develops in and after a strong bend in the tube. Spiraling

Hemodynamic modelling of BOLD fMRI - A machine learning approach

DEFF Research Database (Denmark)

Jacobsen, Danjal Jakup

2007-01-01

This Ph.D. thesis concerns the application of machine learning methods to hemodynamic models for BOLD fMRI data. Several such models have been proposed by different researchers, and they have in common a basis in physiological knowledge of the hemodynamic processes involved in the generation...... of the BOLD signal. The BOLD signal is modelled as a non-linear function of underlying, hidden (non-measurable) hemodynamic state variables. The focus of this thesis work has been to develop methods for learning the parameters of such models, both in their traditional formulation, and in a state space...... formulation. In the latter, noise enters at the level of the hidden states, as well as in the BOLD measurements themselves. A framework has been developed to allow approximate posterior distributions of model parameters to be learned from real fMRI data. This is accomplished with Markov chain Monte Carlo...

Hemodynamic Effects of Noninvasive Ventilation in Patients with Venocapillary Pulmonary Hypertension

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André Moreira Bento

2014-11-01

Full Text Available Background: The hemodynamic effects of noninvasive ventilation with positive pressure in patients with pulmonary hypertension without left ventricular dysfunction are not clearly established. Objectives: Analyze the impact of increasing airway pressure with continuous positive airway pressure on hemodynamic parameters and, in particular, on cardiac output in patients with variable degrees of pulmonary hypertension. Methods: The study included 38 patients with pulmonary hypertension caused by mitral stenosis without left ventricular dysfunction or other significant valvulopathy. The hemodynamic state of these patients was analyzed in three conditions: baseline, after continuous positive pressure of 7 cmH2O and, finally, after pressure of 14 cmH2O. Results: The population was composed of predominantly young and female individuals with significant elevation in pulmonary arterial pressure (mean systolic pressure of 57 mmHg. Of all variables analyzed, only the right atrial pressure changed across the analyzed moments (from the baseline condition to the pressure of 14 cmH2O there was a change from 8 ± 4 mmHg to 11 ± 3 mmHg, respectively, p = 0.031. Even though there was no variation in mean cardiac output, increased values in pulmonary artery pressure were associated with increased cardiac output. There was no harmful effect or other clinical instability associated with use application of airway pressure. Conclusion: In patients with venocapillary pulmonary hypertension without left ventricular dysfunction, cardiac output response was directly associated with the degree of pulmonary hypertension. The application of noninvasive ventilation did not cause complications directly related to the ventilation systems.

Thallium-201 myocardial imaging in unstable angina and variant angina

International Nuclear Information System (INIS)

Wackers, F.J.Th.; Lie, K.I.; Liem, K.L.; Sokole, E.B.; Schoot, J.B. van der

1980-01-01

It is of clinical relevance in the coronary care unit to evaluate the potential role of 201 Tl scintigraphy in patients with unstable angina. In the present chapter the authors discuss 1) the pattern of 201 Tl scintigraphy in patients with unstable angina; and 2) the potential predictive value of 201 Tl scintigraphy in identifying patients with unstable angina who have a poorer prognosis or greater tendency to subsequently develop acute myocardial infarction. All patients with unstable angina pectoris were purposely studied during the pain free period. It seemed conceivable that injecting 201 Tl during an anginal attack would result in a high percentage of scintigraphic defects and probably diminish a potential discriminative value of the method. Moreover in clinical practice the majority of patients arrive at the coronary care unit some time after the last anginal attack. If a diagnostic test performed at this time could distinguish high and low risk patients, important therapeutic decisions might be made at the earliest possible times. (Auth.)

Towards a geophysical decision-support system for monitoring and managing unstable slopes

Science.gov (United States)

Chambers, J. E.; Meldrum, P.; Wilkinson, P. B.; Uhlemann, S.; Swift, R. T.; Inauen, C.; Gunn, D.; Kuras, O.; Whiteley, J.; Kendall, J. M.

2017-12-01

Conventional approaches for condition monitoring, such as walk over surveys, remote sensing or intrusive sampling, are often inadequate for predicting instabilities in natural and engineered slopes. Surface observations cannot detect the subsurface precursors to failure events; instead they can only identify failure once it has begun. On the other hand, intrusive investigations using boreholes only sample a very small volume of ground and hence small scale deterioration process in heterogeneous ground conditions can easily be missed. It is increasingly being recognised that geophysical techniques can complement conventional approaches by providing spatial subsurface information. Here we describe the development and testing of a new geophysical slope monitoring system. It is built around low-cost electrical resistivity tomography instrumentation, combined with integrated geotechnical logging capability, and coupled with data telemetry. An automated data processing and analysis workflow is being developed to streamline information delivery. The development of this approach has provided the basis of a decision-support tool for monitoring and managing unstable slopes. The hardware component of the system has been operational at a number of field sites associated with a range of natural and engineered slopes for up to two years. We report on the monitoring results from these sites, discuss the practicalities of installing and maintaining long-term geophysical monitoring infrastructure, and consider the requirements of a fully automated data processing and analysis workflow. We propose that the result of this development work is a practical decision-support tool that can provide near-real-time information relating to the internal condition of problematic slopes.

Relevant signs of stable and unstable thoracolumbar vertebral column trauma

International Nuclear Information System (INIS)

Gehweiler, J.A.; Daffner, R.H.; Osborne, R.L.

1981-01-01

One-hundred and seventeen patients with acute thoracolumbar vertebral column fracture or fracture-dislocations were analyzed and classified into stable (36%) and unstable (64%). Eight helpful roentgen signs were observed that may serve to direct attention to serious underlying, often occult, fractures and dislocations. The changes fall into four principal groups: abnormal soft tissues, abnormal vertebral alignment, abnormal joints, and widened vertebral canal. All stable and unstable lesions showed abnormal soft tissues, while 70% demonstrated kyphosis and/or scoliosis, and an abnormal adjacent intervertebral disk space. All unstable lesions showed one or more of the following signs: displaced vertebra, widened interspinous space, abnormal apophyseal joint(s), and widened vertebral canal. (orig.)

Application of near-infrared spectroscopy to measurement of hemodynamic signals accompanying stimulated saliva secretion.

Science.gov (United States)

Sato, Hiroki; Obata, Akiko N; Moda, Ichiro; Ozaki, Kazutaka; Yasuhara, Takaomi; Yamamoto, Yukari; Kiguchi, Masashi; Maki, Atsushi; Kubota, Kisou; Koizumi, Hideaki

2011-04-01

We aim to test the feasibility of using near-infrared spectroscopy (NIRS) for indirect measurement of human saliva secretion in response to taste stimuli for potential application to organoleptic testing. We use an NIRS system to measure extracranial hemodynamics (Hb-signals around the temples) of healthy participants when taste stimuli are taken in their mouths. First, the Hb-signals and volume of expelled saliva (stimulated by distilled-water or sucrose-solution intake) are simultaneously measured and large Hb-signal changes in response to the taste stimuli (Hb-responses) are found. Statistical analysis show that both the Hb response and saliva volume are larger for the sucrose solution than for the distilled water with a significant correlation between them (r = 0.81). The effects of swallowing on the Hb-signals are investigated. Similar Hb responses, differing from the sucrose solution and distilled water, are obtained even though the participants swallow the mouth contents. Finally, functional magnetic resonance imaging is used to identify possible sources of the Hb signals corresponding to salivation. Statistical analysis indicates similar responses in the extracranial regions, mainly around the middle meningeal artery. In conclusion, the identified correlation between extracranial hemodynamics and the saliva volume suggests that NIRS is applicable to the measurement of hemodynamic signals accompanying stimulated saliva secretion.

Monitoring Unstable Glaciers with Seismic Noise Interferometry

Science.gov (United States)

Preiswerk, L. E.; Walter, F.

2016-12-01

Gravity-driven glacier instabilities are a threat to human infrastructure in alpine terrain, and this hazard is likely to increase with future changes in climate. Seismometers have been used previously on hazardous glaciers to monitor the natural englacial seismicity. In some situations, an increase in "icequake" activity may indicate fracture growth and thus an imminent major break-off. However, without independent constraints on unstable volumes, such mere event counting is of little use. A promising new approach to monitor unstable masses in Alpine terrain is coda wave interferometry of ambient noise. While already established in the solid earth, application to glaciers is not straightforward, because the lack of inhomogeneities typically suppresses seismic coda waves in glacier ice. Only glaciers with pervasive crevasses provide enough scattering to generate long codas. This is requirement is likely met for highly dynamic unstable glaciers. Here, we report preliminary results from a temporary 5-station on-ice array of seismometers (corner frequencies: 1 Hz, array aperture: 500m) on Bisgletscher (Switzerland). The seismometers were deployed in shallow boreholes, directly above the unstable tongue of the glacier. In the frequency band 4-12 Hz, we find stable noise cross-correlations, which in principle allows monitoring on a subdaily scale. The origin and the source processes of the ambient noise in these frequencies are however uncertain. As a first step, we evaluate the stability of the sources in order to separate effects of changing source parameters from changes of englacial properties. Since icequakes occurring every few seconds may dominate the noise field, we compare their temporal and spatial occurrences with the cross-correlation functions (stability over time, the asymmetry between causal and acausal parts of the cross-correlation functions) as well as with results from beamforming to assess the influence of these transient events on the noise field.

Consenso brasileiro de monitorização e suporte hemodinâmico - Parte V: suporte hemodinâmico Brazilian consensus of monitoring and hemodynamic support - Part V: hemodynamic support

Directory of Open Access Journals (Sweden)

Suzana Margareth Ajeje Lobo

2006-06-01

not reverted irreversible cellular injury establishes. Shock treatment has as its initial priority the fast and vigorous correction of mean arterial pressure and cardiac output to maintain life and avoid or lessen organic dysfunctions. Fluid challenge and vasoactive drugs are necessary to warrant an adequate tissue perfusion and maintenance of function of different organs and systems, always guided by cardiovascular monitorization. The recommendations built in this consensus are aimed to guide hemodynamic support needed to maintain adequate tisular perfusion. METHODS: Modified Delphi methodology was used to create and quantify the consensus between the participants. AMIB indicated a coordinator who invited more six experts in the area of monitoring and hemodynamic support to constitute the Consensus Advisory Board. Twenty five physician and two nurses selected from different regions of the country completed the expert panel, which reviewed the pertinent bibliography listed at the MEDLINE in the period from 1996 to 2004. RESULTS: Recommendations were made answering 17 questions about hemodynamic support with focus on fluid challenge, red blood cell transfusions, vasoactive drugs and perioperative hemodynamic optimization. CONCLUSIONS: Hemodynamic monitoring by itself does not reduce the mortality of critically ill patients, however, we believe that the correct interpretation of the data obtained by the hemodynamic monitoring and the use of hemodynamic support protocols based on well defined tissue perfusion goals can improve the outcome of these patients.

The Effects of Hemodynamic Changes on Pulse Wave Velocity in Cardiothoracic Surgical Patients

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Yurie Obata

2016-01-01

Full Text Available The effect of blood pressure on pulse wave velocity (PWV is well established. However, PWV variability with acute hemodynamic changes has not been examined in the clinical setting. The aim of the present study is to investigate the effect of hemodynamic changes on PWV in patients who undergo cardiothoracic surgery. Using data from 25 patients, we determined blood pressure (BP, heart rate (HR, and the left ventricular outflow tract (LVOT velocity-time integral. By superimposing the radial arterial waveform on the continuous wave Doppler waveform of the LVOT, obtained by transesophageal echo, we were able to determine pulse transit time and to calculate PWV, stroke volume (SV, cardiac output (CO, and systemic vascular resistance (SVR. Increases in BP, HR, and SVR were associated with higher values for PWV. In contrast increases in SV were associated with decreases in PWV. Changes in CO were not significantly associated with PWV.

The numerical simulation study of hemodynamics of the new dense-mesh stent

Science.gov (United States)

Ma, Jiali; Yuan, Zhishan; Yu, Xuebao; Feng, Zhaowei; Miao, Weidong; Xu, Xueli; Li, Juntao

2017-09-01

The treatment of aortic aneurysm in new dense mesh stent is based on the principle of hemodynamic changes. But the mechanism is not yet very clear. This paper analyzed and calculated the hemodynamic situation before and after the new dense mesh stent implanting by the method of numerical simulation. The results show the dense mesh stent changed and impacted the blood flow in the aortic aneurysm. The changes include significant decrement of blood velocity, pressure and shear forces, while ensuring blood can supply branches, which means the new dense mesh stent's hemodynamic mechanism in the treatment of aortic aneurysm is clearer. It has very important significance in developing new dense mesh stent in order to cure aortic aneurysm.

Impact of Intra-Extracranial Hemodynamics on Cerebral Ischemia by Arterial Hypertension (Part 2

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Alexander G. Kruglov, PhD, ScD

2012-06-01

Full Text Available The association between hemodynamic and biochemical parameters of cerebral blood flow have been studied in man, using mathematical methods of statistics. The values have been obtained through catheterization using a probe jammed at the level of the bulb of the superior jugular vein. Relationships with central hemodynamic parameters have been evaluated, including the right atrium, the right ventricle, and the left ventricle, as well as with pressure and biochemical values of the arterial bed. Data have been acquired in patients with stable arterial hypertension. Analysis of all relationship between hemodynamic and biochemical parameters has shown that the uniform hemodynamic zone: Sin.P. – SJV – SEV – the right atrium, normally participates in regulation of gaseous exchange in the human brain depending on the minimum pressure on the way of outflow from the brain. In stable arterial hypertension, this type of regulation is lost. On the basis of the results of this study, it has been concluded that blood viscosity is normally a primary controlled parameter of homeostasis. In stable arterial hypertension, homeostatic control of factors determining rheological and thrombogenic properties of blood, as well as participating in the development of brain ischemic conditions is lost. This increases risk of disturbances in central hemodynamics.

Fermented ginseng, GBCK25, ameliorates hemodynamic function on experimentally induced myocardial injury

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Adithan Aravinthan

2016-10-01

Full Text Available In the present study, we investigated whether treatment with GBCK25 facilitated the recovery of hemodynamic parameters, left ventricle systolic pressure, left ventricular developed pressure, and electrocardiographic changes. GBCK25 significantly prevented the decrease in hemodynamic parameters and ameliorated the electrocardiographic abnormality. These results indicate that GBCK25 has distinct cardioprotective effects in rat heart.

Weak gravitational lensing as a method to constrain unstable dark matter

International Nuclear Information System (INIS)

Wang Meiyu; Zentner, Andrew R.

2010-01-01

The nature of the dark matter remains a mystery. The possibility of an unstable dark matter particle decaying to invisible daughter particles has been explored many times in the past few decades. Meanwhile, weak gravitational lensing shear has gained a lot of attention as a probe of dark energy, though it was previously considered a dark matter probe. Weak lensing is a useful tool for constraining the stability of the dark matter. In the coming decade a number of large galaxy imaging surveys will be undertaken and will measure the statistics of cosmological weak lensing with unprecedented precision. Weak lensing statistics are sensitive to unstable dark matter in at least two ways. Dark matter decays alter the matter power spectrum and change the angular diameter distance-redshift relation. We show how measurements of weak lensing shear correlations may provide the most restrictive, model-independent constraints on the lifetime of unstable dark matter. Our results rely on assumptions regarding nonlinear evolution of density fluctuations in scenarios of unstable dark matter and one of our aims is to stimulate interest in theoretical work on nonlinear structure growth in unstable dark matter models.

Muscular outputs during dynamic bench press under stable versus unstable conditions.

Science.gov (United States)

Koshida, Sentaro; Urabe, Yukio; Miyashita, Koji; Iwai, Kanzunori; Kagimori, Aya

2008-09-01

Previous studies have suggested that resistance training exercise under unstable conditions decreases the isometric force output, yet little is known about its influence on muscular outputs during dynamic movement. The objective of this study was to investigate the effect of an unstable condition on power, force, and velocity outputs during the bench press. Twenty male collegiate athletes (mean age, 21.3 +/- 1.5 years; mean height, 167.7 +/- 7.7 cm; mean weight, 75.9 +/- 17.5 kg) participated in this study. Each subject attempted 3 sets of single bench presses with 50% of 1 repetition maximum (1RM) under a stable condition with a flat bench and an unstable condition with a Swiss ball. Acceleration data were obtained with an accelerometer attached to the center of a barbell shaft, and peak outputs of power, force, and velocity were computed. Although significant loss of the peak outputs was found under the unstable condition (p velocity outputs, compared with previous findings. Such small reduction rates of muscular outputs may not compromise the training effect. Prospective studies are necessary to confirm whether the resistance training under an unstable condition permits the improvement of dynamic performance and trunk stability.

Estimation scheme for unstable ductile fracture of pressure vessel

International Nuclear Information System (INIS)

Takahashi, Jun; Okamura, Hiroyuki; Sakai, Shinsuke

1990-01-01

This paper presents a new scheme for the estimation of unstable ductile fracture using the J-integral. The proposed method uses a load-versus-displacement diagram which is generated using fully plastic solutions. By this method, the phenomena of the ductile fracture can be grasped visually. Thus, the parametrical survey can be executed far more easily than before. Then, using the proposed method, unstable ductile fracture is analyzed for single-edge cracked plates under both uniform tension and pure bending. In addition, several parametrical surveys are performed concerning (1) J-controlled crack growth, (2) compliance of the structure, (3) ductility of the material (i.e., J-resistance curve), and (4) scale of the structure (i.e., screening criterion). As a result, it is shown that the proposed method is especially effective for the paramtrical study of unstable ductile fracture. (author)

In vivo study of rat cortical hemodynamics using a stereotaxic-apparatus-compatible photoacoustic microscope.

Science.gov (United States)

Guo, Heng; Chen, Qian; Qi, Weizhi; Chen, Xingxing; Xi, Lei

2018-04-19

Brain imaging is an important technique in cognitive neuroscience. In this article, we designed a stereotaxic-apparatus-compatible photoacoustic microscope for the studies of rat cortical hemodynamics. Compared with existing optical resolution photoacoustic microscopy (ORPAM) systems, the probe owns feature of fast, light and miniature. In this microscope, we integrated a miniaturized ultrasound transducer with a center frequency of 10 MHz to detect photoacoustic signals and a 2-dimensional (2D) microelectromechanical system (MEMS) scanner to achieve raster scanning of the optical focus. Based on phantom evaluation, this imaging probe has a high lateral resolution of 3.8 μm and an effective imaging domain of 2 × 2 mm 2 . Different from conventional ORPAMs, combining with standard stereotaxic apparatus enables broad studies of rodent brains without any motion artifact. To show its capability, we successfully captured red blood cell flow in the capillary, monitored the vascular changes during bleeding and blood infusion and visualized cortical hemodynamics induced by middle cerebral artery occlusion. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thin disk laser with unstable resonator and reduced output coupler

Science.gov (United States)

Gavili, Anwar; Shayganmanesh, Mahdi

2018-05-01

In this paper, feasibility of using unstable resonator with reduced output coupling in a thin disk laser is studied theoretically. Unstable resonator is modeled by wave-optics using Collins integral and iterative method. An Yb:YAG crystal with 250 micron thickness is considered as a quasi-three level active medium and modeled by solving rate equations of energy levels populations. The amplification of laser beam in the active medium is calculated based on the Beer-Lambert law and Rigrod method. Using generalized beam parameters method, laser beam parameters like, width, divergence, M2 factor, output power as well as near and far-field beam profiles are calculated for unstable resonator. It is demonstrated that for thin disk laser (with single disk) in spite of the low thickness of the disk which leads to low gain factor, it is possible to use unstable resonator (with reduced output coupling) and achieve good output power with appropriate beam quality. Also, the behavior of output power and beam quality versus equivalent Fresnel number is investigated and optimized value of output coupling for maximum output power is achieved.

Induced Hypothermia Does Not Harm Hemodynamics after Polytrauma: A Porcine Model

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Matthias Weuster

2015-01-01

Full Text Available Background. The deterioration of hemodynamics instantly endangers the patients’ life after polytrauma. As accidental hypothermia frequently occurs in polytrauma, therapeutic hypothermia still displays an ambivalent role as the impact on the cardiopulmonary function is not yet fully understood. Methods. We have previously established a porcine polytrauma model including blunt chest trauma, penetrating abdominal trauma, and hemorrhagic shock. Therapeutic hypothermia (34°C was induced for 3 hours. We documented cardiovascular parameters and basic respiratory parameters. Pigs were euthanized after 15.5 hours. Results. Our polytrauma porcine model displayed sufficient trauma impact. Resuscitation showed adequate restoration of hemodynamics. Induced hypothermia had neither harmful nor major positive effects on the animals’ hemodynamics. Though heart rate significantly decreased and mixed venous oxygen saturation significantly increased during therapeutic hypothermia. Mean arterial blood pressure, central venous pressure, pulmonary arterial pressure, and wedge pressure showed no significant differences comparing normothermic trauma and hypothermic trauma pigs during hypothermia. Conclusions. Induced hypothermia after polytrauma is feasible. No major harmful effects on hemodynamics were observed. Therapeutic hypothermia revealed hints for tissue protective impact. But the chosen length for therapeutic hypothermia was too short. Nevertheless, therapeutic hypothermia might be a useful tool for intensive care after polytrauma. Future studies should extend therapeutic hypothermia.

Induced Hypothermia Does Not Harm Hemodynamics after Polytrauma: A Porcine Model

Science.gov (United States)

Mommsen, Philipp; Pfeifer, Roman; Mohr, Juliane; Ruchholtz, Steffen; Flohé, Sascha; Fröhlich, Matthias; Keibl, Claudia; Seekamp, Andreas; Witte, Ingo

2015-01-01

Background. The deterioration of hemodynamics instantly endangers the patients' life after polytrauma. As accidental hypothermia frequently occurs in polytrauma, therapeutic hypothermia still displays an ambivalent role as the impact on the cardiopulmonary function is not yet fully understood. Methods. We have previously established a porcine polytrauma model including blunt chest trauma, penetrating abdominal trauma, and hemorrhagic shock. Therapeutic hypothermia (34°C) was induced for 3 hours. We documented cardiovascular parameters and basic respiratory parameters. Pigs were euthanized after 15.5 hours. Results. Our polytrauma porcine model displayed sufficient trauma impact. Resuscitation showed adequate restoration of hemodynamics. Induced hypothermia had neither harmful nor major positive effects on the animals' hemodynamics. Though heart rate significantly decreased and mixed venous oxygen saturation significantly increased during therapeutic hypothermia. Mean arterial blood pressure, central venous pressure, pulmonary arterial pressure, and wedge pressure showed no significant differences comparing normothermic trauma and hypothermic trauma pigs during hypothermia. Conclusions. Induced hypothermia after polytrauma is feasible. No major harmful effects on hemodynamics were observed. Therapeutic hypothermia revealed hints for tissue protective impact. But the chosen length for therapeutic hypothermia was too short. Nevertheless, therapeutic hypothermia might be a useful tool for intensive care after polytrauma. Future studies should extend therapeutic hypothermia. PMID:26170533

Effects of radiation, burn and combined radiation-burn injury on hemodynamics

International Nuclear Information System (INIS)

Ye Benlan; Cheng Tianming; Xiao Jiasi

1996-01-01

Changes in hemodynamics after radiation, burn and combined radiation burn injury within eight hours post injury were studied. The results indicate: (1) Shock of rats in the combined injury group is more severe than that in the burn group. One of the reasons is that the blood volume in the combined injury group is less than that in the burn group. Radiation injury plays an important role in this effect, which enhances the increase in vascular permeability and causes the loss of plasma. (2) Decrease in cardiac output and stroke work and increase in vascular resistance in the combined radiation burn group are more drastic than those in the burn group, which may cause and enhance shock. Replenishing fluid is useful for recovery of hemodynamics. (3) Rb uptake is increased in the radiation group which indicates that compensated increase of myocardial nutritional blood flow may take place before the changes of hemodynamics and shock. Changes of Rb uptake in the combined injury group is different from that in the radiation groups and in the burn group. The results also suggest that changes of ion channel activities may occur to a different extent after injury. (4) Verapamil is helpful to the recovery of hemodynamics post injury. It is better to combine verapamil with replenishing fluid

Hemodynamic Effect of Laser Therapy in Spontaneously Hypertensive Rats

Energy Technology Data Exchange (ETDEWEB)

Tomimura, Suely, E-mail: suelytomimura@uol.com.br [Programa de Pós-Graduação em Biofotônica em Ciências da Saúde da Universidade Nove de Julho (UNINOVE) (Brazil); Silva, Bianca Passos Assumpção [Programa de Graduação e Pós-Graduação em Medicina da UNINOVE (Brazil); Sanches, Iris Callado [Laboratório de Fisiologia Translacional da UNINOVE (Brazil); Canal, Marina [Programa de Graduação e Pós-Graduação em Medicina da UNINOVE (Brazil); Consolim-Colombo, Fernanda [Programa de Graduação e Pós-Graduação em Medicina da UNINOVE (Brazil); Unidade de Hipertensão e Central Médica de Laser do Instituto do Coração - Hospital das Clinicas da Faculdade de Medicina da Universidade de São Paulo (InCor/HC-FMUSP), São Paulo, SP (Brazil); Conti, Felipe Fernandes; Angelis, Katia De [Laboratório de Fisiologia Translacional da UNINOVE (Brazil); Chavantes, Maria Cristina [Programa de Pós-Graduação em Biofotônica em Ciências da Saúde da Universidade Nove de Julho (UNINOVE) (Brazil); Programa de Graduação e Pós-Graduação em Medicina da UNINOVE (Brazil); Unidade de Hipertensão e Central Médica de Laser do Instituto do Coração - Hospital das Clinicas da Faculdade de Medicina da Universidade de São Paulo (InCor/HC-FMUSP), São Paulo, SP (Brazil)

2014-08-15

Systemic arterial hypertension (SAH) is considered to be the greatest risk factor for the development of neuro-cardiovascular pathologies, thus constituting a severe Public Health issue in the world. The Low-Level Laser Therapy (LLLT), or laser therapy, activates components of the cellular structure, therefore converting luminous energy into photochemical energy and leading to biophysical and biochemical reactions in the mitochondrial respiratory chain. The LLLT promotes cellular and tissue photobiomodulation by means of changes in metabolism, leading to molecular, cellular and systemic changes. The objective of this study was to analyze the action of low-level laser in the hemodynamic modulation of spontaneously hypertensive rats, in the long term. Animals (n = 16) were randomly divided into the Laser Group (n = 8), which received three weekly LLLT irradiations for seven weeks, and into the Sham Group (n = 8), which received three weekly simulations of laser for seven weeks, accounting for 21 applications in each group. After seven weeks, animals were cannulated by the implantation of a catheter in the left carotid artery. On the following day, the systemic arterial pressure was recorded. The Laser Group showed reduced levels of mean blood pressure, with statistically significant reduction (169 ± 4 mmHg* vs. 182 ± 4 mmHg from the Sham Group) and reduced levels of diastolic pressure (143 ± 4 mmHg* vs. 157 ± 3 mmHg from the Sham Group), revealing a 13 and 14 mmHg decrease, respectively. Besides, there was a concomitant important decline in heart rate (312 ± 14 bpm vs. 361 ± 13 bpm from the Sham Group). Therefore, laser therapy was able to produce hemodynamic changes, thus reducing pressure levels in spontaneously hypertensive rats.

Hemodynamic Effect of Laser Therapy in Spontaneously Hypertensive Rats

Directory of Open Access Journals (Sweden)

Suely Tomimura

2014-08-01

Full Text Available Systemic arterial hypertension (SAH is considered to be the greatest risk factor for the development of neuro-cardiovascular pathologies, thus constituting a severe Public Health issue in the world. The Low-Level Laser Therapy (LLLT, or laser therapy, activates components of the cellular structure, therefore converting luminous energy into photochemical energy and leading to biophysical and biochemical reactions in the mitochondrial respiratory chain. The LLLT promotes cellular and tissue photobiomodulation by means of changes in metabolism, leading to molecular, cellular and systemic changes. The objective of this study was to analyze the action of low-level laser in the hemodynamic modulation of spontaneously hypertensive rats, in the long term. Animals (n = 16 were randomly divided into the Laser Group (n = 8, which received three weekly LLLT irradiations for seven weeks, and into the Sham Group (n = 8, which received three weekly simulations of laser for seven weeks, accounting for 21 applications in each group. After seven weeks, animals were cannulated by the implantation of a catheter in the left carotid artery. On the following day, the systemic arterial pressure was recorded. The Laser Group showed reduced levels of mean blood pressure, with statistically significant reduction (169 ± 4 mmHg* vs. 182 ± 4 mmHg from the Sham Group and reduced levels of diastolic pressure (143 ± 4 mmHg* vs. 157 ± 3 mmHg from the Sham Group, revealing a 13 and 14 mmHg decrease, respectively. Besides, there was a concomitant important decline in heart rate (312 ± 14 bpm vs. 361 ± 13 bpm from the Sham Group. Therefore, laser therapy was able to produce hemodynamic changes, thus reducing pressure levels in spontaneously hypertensive rats.

Beneficial hemodynamic effects of nicorandil in a canine model of acute congestive heart failure: comparison with nitroglycerin and cromakalim.

Science.gov (United States)

Noguchi, K; Matsuzaki, T; Ojiri, Y; Koyama, T; Nakasone, J; Sakanashi, M

1998-01-01

Comparative hemodynamic effects of nicorandil (NCR), nitroglycerin (NTG) and cromakalim (CRM) were examined in a canine model of acute congestive heart failure (CHF). CHF was produced by injections of saponin into coronary arteries of anesthetized dogs followed by volume loading and continuous i.v. infusion of methoxamine. After the treatment, aortic blood flow (AoF), left ventricular dP/dt and myocardial segment shortening (SS) markedly decreased, while the left ventricular end-diastolic pressure (LVEDP), the right atrial pressure (RAP) and the systemic vascular resistance (SVR) increased. NCR (n = 6), NTG (n = 6) and CRM (n = 8), which were administered i.v. after production of CHF, caused a comparable reduction in LVEDP. NCR and CRM profoundly increased AoF and SS but NTG did only slightly. On the other hand, NTG and NCR but not CRM significantly reduced RAP. Intracoronary NCR (n = 8) exerted no or similar effects on SS as well as systemic hemodynamic indices to those observed with i.v. NCR despite distinct coronary vasodilation. These results indicate that NCR may exert beneficial hemodynamic effects in an experimental CHF mainly due to lessening both afterload and preload rather than the coronary vasodilating effect.

Incidence and follow-up of Braunwald subgroups in unstable angina pectoris

NARCIS (Netherlands)

van Miltenburg-van Zijl, A. J.; Simoons, M. L.; Veerhoek, R. J.; Bossuyt, P. M.

1995-01-01

OBJECTIVES. This study was performed to establish the prognosis of patients with unstable angina within the subgroups of the Braunwald classification. BACKGROUND. Among many classifications of unstable angina, the Braunwald classification is frequently used. However, the incidence and risk for each

Continuous Hemodynamic Monitoring in Acute Stroke: An Exploratory Analysis

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Ayan Sen

2014-07-01

Full Text Available Introduction: Non-invasive, continuous hemodynamic monitoring is entering the clinical arena. The primary objective of this study was to test the feasibility of such monitoring in a pilot sample of Emergency Department (ED stroke patients. Secondary objectives included analysis of hemodynamic variability and correlation of continuous blood pressure measurements with standard measurements. Methods: This study was a secondary analysis of 7 stroke patients from a prospectively collected data set of patients that received 2 hours of hemodynamic monitoring in the ED. Stroke patients were included if hemorrhagic or ischemic stroke was confirmed by neuroimaging, and symptom onset was within 24 hours. They were excluded for the presence of a stroke mimic or transient ischemic attack. Monitoring was performed using the Nexfin device (Edwards Lifesciences, Irvine CA. Results: The mean age of the cohort was 71 ± 17 years, 43% were male, and the mean National Institute of Health Stroke Scale (NIHSS was 6.9 ± 5.5. Two patients had hemorrhagic stroke. We obtained 42,456 hemodynamic data points, including beat-to-beat blood pressure measurements with variability of 18 mmHg and cardiac indices ranging from 1.8 to 3.6 l/min/m2. The correlation coefficient between continuous blood pressure measurements with the Nexfin device and standard ED readings was 0.83. Conclusion: This exploratory investigation revealed that continuous, noninvasive monitoring in the ED is feasible in acute stroke. Further research is currently underway to determine how such monitoring may impact outcomes in stroke or replace the need for invasive monitoring. [West J Emerg Med. 2014;15(4:–0.

Development of atomic-beam resonance method to measure the nuclear moments of unstable nuclei

Energy Technology Data Exchange (ETDEWEB)

Sugimoto, T., E-mail: sugimoto@ribf.riken.jp [SPring-8 (Japan); Asahi, K. [Tokyo Institute of Technology, Department of Physics (Japan); Kawamura, H.; Murata, J. [Rikkyo University, Department of Physics (Japan); Nagae, D.; Shimada, K. [Tokyo Institute of Technology, Department of Physics (Japan); Ueno, H.; Yoshimi, A. [RIKEN Nishina Center (Japan)

2008-01-15

We have been working on the development of a new technique of atomic-beam resonance method to measure the nuclear moments of unstable nuclei. In the present study, an ion-guiding system to be used as an atomic-beam source have been developed.

On the Kalman Filter error covariance collapse into the unstable subspace

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A. Trevisan

2011-03-01

Full Text Available When the Extended Kalman Filter is applied to a chaotic system, the rank of the error covariance matrices, after a sufficiently large number of iterations, reduces to N⁺ + N⁰ where N⁺ and N⁰ are the number of positive and null Lyapunov exponents. This is due to the collapse into the unstable and neutral tangent subspace of the solution of the full Extended Kalman Filter. Therefore the solution is the same as the solution obtained by confining the assimilation to the space spanned by the Lyapunov vectors with non-negative Lyapunov exponents. Theoretical arguments and numerical verification are provided to show that the asymptotic state and covariance estimates of the full EKF and of its reduced form, with assimilation in the unstable and neutral subspace (EKF-AUS are the same. The consequences of these findings on applications of Kalman type Filters to chaotic models are discussed.

Review article: closed-loop systems in anesthesia: is there a potential for closed-loop fluid management and hemodynamic optimization?

Science.gov (United States)

Rinehart, Joseph; Liu, Ngai; Alexander, Brenton; Cannesson, Maxime

2012-01-01

Closed-loop (automated) controllers are encountered in all aspects of modern life in applications ranging from air-conditioning to spaceflight. Although these systems are virtually ubiquitous, they are infrequently used in anesthesiology because of the complexity of physiologic systems and the difficulty in obtaining reliable and valid feedback data from the patient. Despite these challenges, closed-loop systems are being increasingly studied and improved for medical use. Two recent developments have made fluid administration a candidate for closed-loop control. First, the further description and development of dynamic predictors of fluid responsiveness provides a strong parameter for use as a control variable to guide fluid administration. Second, rapid advances in noninvasive monitoring of cardiac output and other hemodynamic variables make goal-directed therapy applicable for a wide range of patients in a variety of clinical care settings. In this article, we review the history of closed-loop controllers in clinical care, discuss the current understanding and limitations of the dynamic predictors of fluid responsiveness, and examine how these variables might be incorporated into a closed-loop fluid administration system.

Novel Use of a Noninvasive Hemodynamic Monitor in a Personalized, Active Learning Simulation

Science.gov (United States)

Zoller, Jonathan K.; He, Jianghua; Ballew, Angela T.; Orr, Walter N.; Flynn, Brigid C.

2017-01-01

The present study furthered the concept of simulation-based medical education by applying a personalized active learning component. We tested this novel approach utilizing a noninvasive hemodynamic monitor with the capability to measure and display in real time numerous hemodynamic parameters in the exercising participant. Changes in medical…

Quantification of collateral flow in humans: a comparison of angiographic, electrocardiographic and hemodynamic variables

NARCIS (Netherlands)

van Liebergen, R. A.; Piek, J. J.; Koch, K. T.; de Winter, R. J.; Schotborgh, C. E.; Lie, K. I.

1999-01-01

Evaluation of collateral vascular circulation according to hemodynamic variables and its relation to myocardial ischemia. There is limited information regarding the hemodynamic quantification of recruitable collateral vessels. Angiography of the donor coronary artery was performed before and during

Hemodynamics and vasopressor support in therapeutic hypothermia after cardiac arrest

DEFF Research Database (Denmark)

Bro-Jeppesen, John; Kjaergaard, Jesper; Søholm, Helle

2014-01-01

AIM: Inducing therapeutic hypothermia (TH) in Out-of-Hospital Cardiac Arrest (OHCA) can be challenging due to its impact on central hemodynamics and vasopressors are frequently used to maintain adequate organ perfusion. The aim of this study was to assess the association between level of vasopres......AIM: Inducing therapeutic hypothermia (TH) in Out-of-Hospital Cardiac Arrest (OHCA) can be challenging due to its impact on central hemodynamics and vasopressors are frequently used to maintain adequate organ perfusion. The aim of this study was to assess the association between level...

A priori which-way information in quantum interference with unstable particles

International Nuclear Information System (INIS)

Krause, D.E.; Fischbach, E.; Rohrbach, Z.J.

2014-01-01

If an unstable particle used in a two-path interference experiment decays before reaching a detector, which-way information becomes available that reduces the detected interference fringe visibility V. Here we argue that even when an unstable particle does not decay while in the interferometer, a priori which-way information is still available in the form of path predictability P which depends on the particle's decay rate Γ. We further demonstrate that in a matter-wave Mach–Zehnder interferometer using an excited atom with an appropriately tuned cavity, P is related to V through the duality relation P 2 +V 2 =1. - Highlights: • Even undecayed unstable particles exhibit novel interference effects. • Interference is studied in a Mach–Zehnder interferometer with a cavity. • More which-way information is available when using unstable particles. • A relation between which-way information and interference is satisfied

Non-Abelian magnetized blackholes and unstable attractors

International Nuclear Information System (INIS)

Mosaffa, A.E.; Randjbar-Daemi, S.; Sheikh-Jabbari, M.M.

2006-12-01

Fluctuations of non-Abelian gauge fields in a background magnetic flux contain tachyonic modes and hence the background is unstable. We extend these results to the cases where the background flux is coupled to Einstein gravity and show that the corresponding spherically symmetric geometries, which in the absence of a cosmological constant are of the form of Reissner-Nordstroem blackholes or the AdS 2 x S 2 , are also unstable. We discuss the relevance of these instabilities to several places in string theory including various string compactifications and the attractor mechanism. Our results for the latter imply that the attractor mechanism shown to work for the extremal Abelian charged blackholes, cannot be applied in a straightforward way to the extremal non-Abelian colored blackholes. (author)

The Influence of Age on Hemodynamic Parameters During Rest and Exercise in Healthy Individuals

DEFF Research Database (Denmark)

Wolsk, Emil; Bakkestrøm, Rine; Thomsen, Jacob H

2017-01-01

OBJECTIVES: The authors sought to obtain hemodynamic estimates across a wide age span and in both sexes for future reference and compare these estimates with current guideline diagnostic hemodynamic thresholds for abnormal filling pressure and pulmonary hypertension. BACKGROUND: At present....... METHODS: Sixty-two healthy participants, evenly distributed with respect to age (20 to 80 years) and sex (32 women/30 men), were prospectively enrolled in the study. Participants were all deemed healthy by medical history, echocardiography, exercise test, spirometry, blood tests, and electrocardiogram....... Participants had hemodynamic parameters measured using right heart catheterization during rest, passive leg raise, and incremental exercise. RESULTS: During rest, all hemodynamic parameters were similar between age groups, apart from blood pressure. During leg raise and incremental exercise...

Effects of irradiation on the pulmonary hemodynamics and the pulmonary vascular permeability

International Nuclear Information System (INIS)

Ohkuda, Kazuhiro; Watanabe, Shinkichi; Okada, Shinichiroh

1982-01-01

In 4 sheeps, base lines of hemodynamics and lymph dynamics were observed for 2 hours, and then 1,000 rad of 60 Co was irradiated to the inferior lobes of the lung. Pulmonary hemodynamics and lymph dynamics were continuously observed, and water and protein permeability of the irradiated pulmonary vessels was evaluated. In 4 control sheeps, no change in pulmonary hemodynamics and lymph dynamics was noted. In the irradiated group, there was no remarkable change in pulmonary hemodynamics for 6 to 8 hours after 60 Co irradiation. Pulmonary lymph flow began to increase 2 hours after irradiation to about 1.7 times the base line level after 4 hours. The increase in pulmonary lymph flow was accompanied by decrease in plasma protein concentration and increase in protein concentration of the lung lymph, resulting in an apparent increase in the ratio of lymph/plasma protein concentration. Water and protein leak from the pulmonary vessels increased. A photomicroscopic observation revealed dilatation of the lymphatic vessels in the lung interstice and a mild pulmonary interstitial edema. Vascular damage, especially due to increased water and protein permeability of the lung capillary vessels, occurred immediately after 60 Co irradiation. (Ueda, J.)

[Coronary transluminal angioplasty and determination of the intracoronary gradient with a new monorail system].

Science.gov (United States)

Freitas, A D; Medina, A; Bethencourt, A; Coello, I; Hernández, E; Peraza, C; Melian, F; Jiménez, F; Laraudogoitia, E; Goicolea, J

1989-10-01

To evaluate the results obtained in coronary angioplasty using the new very low profile monorail catheter. A retrospective study to define the causes and frequency of successful and unsuccessful coronary angioplasty on proximal and distal lesions located in the three coronary vessels. Patients referred to the Hemodynamic Unit for coronary angioplasty. Coronary angioplasty was performed in 106 patients with cardiac ischemic disease (stable angina, unstable angina and myocardial infarction after thrombolytic therapy). To perform coronary angioplasty using a monorail system, including dilatation of vessels (angioplasty) and to measure the intracoronary gradient. A high success rate was achieved (92%) independent of vessel dilated or of the position of the stenosis. There was a lower success rate in complex lesions. In this study, this newly modified system for coronary angioplasty with balloon catheter and monorail pressure catheter gave a very high performance.

Myocardial hypertrophy and intracardial hemodynamics in children with bicuspid aortic valve

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А. V. Kamenshchyk

2017-08-01

Full Text Available Bicuspid aortic valve is one of the most common congenital heart diseases with low manifestation in childhood and severe consequences in adults that determines the importance in early diagnostics of myocardial changes in this anomaly. According to the literature the polymorphisms in the genes of NFATC family could result both in impaired embriogenetic valves formation and development of postnatal myocardial hypertrophy. The aim of the study was to detect the early changes of intracardial hemodynamics at aortic valve in children with bicuspid aortic valve (BAV and establish their interrelations to the signs of myocardial hypertrophy in these children. Materials and methods: Dopplerograhphic study of basic intracardiac hemodynamics parameters in 38 children with BAV and in 28 children of control group was conducted. The results were processed statistically by Student’s t-test, correlation analysis and multiple regression. Results: In the result of study the moderate concentric left ventricle myocardial hypertrophy development was detected in 62 % of children with BAV which is accompanying to significant increasing of blood flow velocity and pressure gradient at aortic valve. There were not established significant correlations between the parameters of hemodynamics at valve and left ventricle’s posterior wall depth and septum depth whereas the highest inputs of these values were obtained in the left ventricle systolic dimension and volume and less in the hypertrophic signs. Conclusions: In children with BAV the moderate concentric myocardial hypertrophy with significant changes of intracardial hemodynamics at aortic valve takes place with the highest inputs in left ventricle volumetric values The obtained data serves as a substantiation for the treatment and prevention of it further development. bicuspid aortic valve; children; heart hypertrophy; dopplerechocardiography; hemodynamics; regression analysis

Hemodynamic control of in patients with concomitant hypertensive disease during brain aneurysm clipping

OpenAIRE

Dzyuba, D.O.; Melnik, A.F.; Yavorsky, F.A.

2018-01-01

The article describes the state of the problem of hemodynamic control during brain aneurysm clipping in concomitant hypertensive disease. Author studies hemodynamic control by using magnesia therapy with the addition of clonidine solution and infusion of urapidil solution. Based on the results of the study, the advantages of urapidil infusion are given.

Metabolic and hemodynamic effects of saline infusion to maintain volemia on temporary abdominal aortic occlusion

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Fábio Ferreira Amorim

2002-10-01

Full Text Available OBJECTIVE: To analyze hemodynamic and metabolic effects of saline solution infusion in the maintenance of blood volume in ischemia-reperfusion syndrome during temporary abdominal aortic occlusion in dogs. METHODS: We studied 20 dogs divided into 2 groups: the ischemia-reperfusion group (IRG, n=10 and the ischemia-reperfusion group with saline solution infusion aiming at maintaining mean pulmonary arterial wedge pressure between 10 and 20 mmHg (IRG-SS, n=10. All animals were anesthetized with sodium thiopental and maintained on spontaneous ventilation. Occlusion of the supraceliac aorta was obtained with inflation of a Fogarty catheter inserted through the femoral artery. After 60 minutes of ischemia, the balloon was deflated, and the animals were observed for another 60 minutes of reperfusion. RESULTS: IRG-SS dogs did not have hemodynamic instability after aortic unclamping, and the mean systemic blood pressure and heart rate were maintained. However, acidosis worsened, which was documented by a greater reduction of arterial pH that occurred especially due to the absence of a respiratory response to metabolic acidosis that was greater with the adoption of this procedure. CONCLUSION: Saline solution infusion to maintain blood volume avoided hemodynamic instability after aortic unclamping. This procedure, however, caused worsening in metabolic acidosis in this experimental model.

[Cerebral hemodynamics in patients with neurosensory hearing loss before and after magnetotherapy].

Science.gov (United States)

Morenko, V M; Enin, I P

2001-01-01

Magnetotherapy effects on cerebral hemodynamics were studied using rheoencephalography (REG). When the treatment results and changes in cerebral hemodynamics were compared it was evident that normalization or improvement of vascular status in vertebrobasilar and carotid territories registered at REG results in better hearing. This confirms the role of vascular factor in pathogenesis of neurosensory hypoacusis of different etiology and effectiveness of magnetotherapy in such patients.

Evolution from electrophysiologic to hemodynamic monitoring: the story of left atrial and pulmonary artery pressure monitors

Directory of Open Access Journals (Sweden)

Deirdre M Mooney

2015-10-01

Full Text Available Heart failure (HF is a costly, challenging and highly prevalent medical condition. Hospitalization for acute decompensation is associated with high morbidity and mortality. Despite application of evidence-based medical therapies and technologies, HF remains a formidable challenge for virtually all healthcare systems. Repeat hospitalizations for acute decompensated HF (ADHF can have major financial impact on institutions and resources. Early and accurate identification of impending ADHF is of paramount importance yet there is limited high quality evidence or infrastructure to guide management in the outpatient setting. Historically, ADHF was identified by physical exam findings or invasive hemodynamic monitoring during a hospital admission; however, advances in medical microelectronics and the advent of device-based diagnostics have enabled long-term ambulatory monitoring of HF patients in the outpatient setting. These monitors have evolved from piggybacking on cardiac implantable electrophysiologic devices to standalone implantable hemodynamic monitors that transduce left atrial or pulmonary artery pressures as surrogate measures of left ventricular filling pressure. As technology evolves, devices will likely continue to miniaturize while their capabilities grow. An important, persistent challenge that remains is developing systems to translate the large volumes of real-time data, particularly data trends, into actionable information that leads to appropriate, safe and timely interventions without overwhelming outpatient cardiology and general medical practices. Future directions for implantable hemodynamic monitors beyond their utility in heart failure may include management of other major chronic diseases such as pulmonary hypertension, end stage renal disease and portal hypertension.

Evolution from electrophysiologic to hemodynamic monitoring: the story of left atrial and pulmonary artery pressure monitors.

Science.gov (United States)

Mooney, Deirdre M; Fung, Erik; Doshi, Rahul N; Shavelle, David M

2015-01-01

Heart failure (HF) is a costly, challenging and highly prevalent medical condition. Hospitalization for acute decompensation is associated with high morbidity and mortality. Despite application of evidence-based medical therapies and technologies, HF remains a formidable challenge for virtually all healthcare systems. Repeat hospitalizations for acute decompensated HF (ADHF) can have major financial impact on institutions and resources. Early and accurate identification of impending ADHF is of paramount importance yet there is limited high quality evidence or infrastructure to guide management in the outpatient setting. Historically, ADHF was identified by physical exam findings or invasive hemodynamic monitoring during a hospital admission; however, advances in medical microelectronics and the advent of device-based diagnostics have enabled long-term ambulatory monitoring of HF patients in the outpatient setting. These monitors have evolved from piggybacking on cardiac implantable electrophysiologic devices to standalone implantable hemodynamic monitors that transduce left atrial or pulmonary artery pressures as surrogate measures of left ventricular filling pressure. As technology evolves, devices will likely continue to miniaturize while their capabilities grow. An important, persistent challenge that remains is developing systems to translate the large volumes of real-time data, particularly data trends, into actionable information that leads to appropriate, safe and timely interventions without overwhelming outpatient cardiology and general medical practices. Future directions for implantable hemodynamic monitors beyond their utility in heart failure may include management of other major chronic diseases such as pulmonary hypertension, end stage renal disease and portal hypertension.

Hemodynamic significance of internal carotid artery disease

DEFF Research Database (Denmark)

Schroeder, T

1988-01-01

Neurologic symptoms in the region of an internal carotid artery stenosis are considered to be embolic in most instances. Only in a subgroup has carotid occlusive disease with impairment of the collateral supply, caused a state of hemodynamic failure with marked reduction of perfusion pressure. Th...

Nonlinear Analysis of an Unstable Bench Press Bar Path and Muscle Activation.

Science.gov (United States)

Lawrence, Michael A; Leib, Daniel J; Ostrowski, Stephanie J; Carlson, Lara A

2017-05-01

Lawrence, MA, Leib, DJ, Ostrowski, SJ, and Carlson, LA. Nonlinear analysis of an unstable bench press bar path and muscle activation. J Strength Cond Res 31(5): 1206-1211, 2017-Unstable resistance exercises are typically performed to improve the ability of stabilizing muscles to maintain joint integrity under a load. The purpose of this study was to examine the effects of an unstable load (as provided by a flexible barbell and a load suspended by elastic bands) on the bar path, the primary musculature, and stabilizing musculature while bench pressing using nonlinear analyses. Fifteen resistance-trained men (age 24.2 ± 2.7 years, mass 84.1 ± 12.0 kg, height 1.77 ± 0.05 m, 9.9 ± 3.4 years of lifting experience, and bench press 1 repetition maximum (RM) 107.5 ± 25.9 kg) volunteered for this study. Subjects pressed 2 sets of 5 repetitions in both stable (total load 75% 1RM) and unstable (total load 60% 1RM) conditions using a standard barbell and a flexible Earthquake bar, respectively. Surface electromyography was used to detect muscle activity of primary movers (pectoralis major, anterior deltoid, and triceps) and bar stabilizing musculature (latissimus dorsi, middle and posterior deltoid, biceps brachii, and upper trapezius). During the unstable condition, the bar moved in more ways and was less predictable in the mediolateral and anteroposterior directions. However, the muscle activation patterns of all muscles were more constrained with the unstable barbell. These findings suggest that the unstable condition was more challenging to control, but subjects controlled the instability by contracting their muscles in a more stable pattern or "staying tight" throughout the exercise.

Effects of thrombin inhibition with melagatran on renal hemodynamics and function and liver integrity during early endotoxemia

DEFF Research Database (Denmark)

Nitescu, Nicoletta; Grimberg, Elisabeth; Ricksten, Sven-Erik

2007-01-01

Sepsis is associated with an activation of the coagulation system and multiorgan failure. The aim of the study was to examine the effects of selective thrombin inhibition with melagatran on renal hemodynamics and function, and liver integrity, during early endotoxemia. Endotoxemia was induced...

Comparing the Rates of Dopamine Hemodynamic Effect Onset after Infusion through Peripheral Veins in Three Regions

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Deokkyu Kim

2017-02-01

Full Text Available Background Dopamine is an inotropic agent that is often selected for continuous infusion. For hemodynamic stability, the rate of infusion is controlled in the range of 5-15 μg/kg/min. This study aimed to compare the time intervals from the administration of dopamine to the onset of its hemodynamic effects when dopamine was administered through three different peripheral veins (the cephalic vein [CV], the great saphenous vein [GSV], and the external jugular vein [EJV]. Methods Patients in group 1, group 2, and group 3 received dopamine infusions in the CV, GSV, and EJV, respectively. A noninvasive continuous cardiac output monitor (NICCOMO™, Medis, Ilmenau, Germany was used to assess cardiac output (CO and systemic vascular resistance (SVR. Six minutes after intubation, baseline heart rate (HR, systolic blood pressure (BP, diastolic BP, mean arterial pressure (MAP, CO, and SVR values were recorded and dopamine infusion was initiated at a dose of 10 μg/kg/min. Hemodynamic changes at 0, 4, 8, 12, and 15 minutes postinfusion were recorded. Results No statistically significant differences were observed among the three groups with respect to the rate of hemodynamic change. In all groups, systolic BP, diastolic BP, MAP, and SVR tended to increase after decreasing for the first 4 minutes; in contrast, HR and CO decreased until 8 minutes, after which they tended to reach a plateau. Conclusions For patients under general anesthesia receiving dopamine at 10 μg/kg/min, there were no clinical differences in the effect of dopamine administered through three different peripheral veins.

Characterization of Hemodynamics in Patients with Idiopathic and Thromboembolic Pulmonary Hypertension

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Carmelle V. Remillard

2008-01-01

Full Text Available Demographic and hemodynamic data from patients with idiopathic pulmonary arterial hypertension (IPAH and chronic thromboembolic pulmonary hypertension (CTEPH have not been systematically characterized to identify differences related to gender, age, race, disease severity, and drug response. Our goal was to define the distribution and relation of IPAH and CTEPH based on these criteria. Hemodynamic and demographic data from 242 IPAH patients and 90 CTEPH patients were collected and compared. IPAH incidence was greater in women, but men had a higher basal mean pulmonary arterial pressure (mPAP. mPAP was comparable among all IPAH ethnic groups. IPAH patients with no history of fenfluramine-phentermine use had a higher mPAP than users. Exercise-induced IPAH was apparent in 14.5% of IPAH patients. Only 9% of IPAH patients responded to inhaled nitric oxide with a ≥20% decrease in mPAP. Compared to CTEPH patients, mPAP was greater but average age of diagnosis was lower in IPAH patients. mPAP negatively correlated with age of diagnosis in IPAH patients only. These results indicate that elevated CO is not the main determinant of mPAP in both IPAH and CTEPH patients. However, the two patient groups differ in terms of their demographic and hemodynamic distributions, and according to the correlation between mPAP and other clinical hemodynamics and demographics.

Physiology of school burnout in medical students: Hemodynamic and autonomic functioning

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Ross W. May

2016-09-01

Full Text Available This study investigated the relationship between burnout and hemodynamic and autonomic functioning in both medical students (N = 55 and premedical undergraduate students (N = 77. Questionnaires screened for health related issues and assessed school burnout and negative affect symptomatology (anxiety and depression. Continuous beat-to-beat blood pressure (BP through finger plethysmography and electrocardiogram (ECG monitoring was conducted during conditions of baseline and cardiac stress induced via the cold pressor task to produce hemodynamic, heart rate variability, and blood pressure variability indices. Independent sample t-tests demonstrated that medical students had significantly higher school burnout scores compared to their undergraduate counterparts. Controlling for age, BMI, anxiety and depressive symptoms, multiple regression analyses indicated that school burnout was a stronger predictor of elevated hemodynamics (blood pressure, decreased heart rate variability, decreased markers of vagal activity and increased markers of sympathetic tone at baseline for medical students than for undergraduates. Analyses of physiological values collected during the cold pressor task indicated greater cardiac hyperactivity for medical students than for undergraduates. The present study supports previous research linking medical school burnout to hemodynamic and autonomic functioning, suggests biomarkers for medical school burnout, and provides evidence that burnout may be implicated as a physiological risk factor in medical students. Study limitations and potential intervention avenues are discussed.

Pharmacological Modulation of Hemodynamics in Adult Zebrafish In Vivo.

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Daniel Brönnimann

Full Text Available Hemodynamic parameters in zebrafish receive increasing attention because of their important role in cardiovascular processes such as atherosclerosis, hematopoiesis, sprouting and intussusceptive angiogenesis. To study underlying mechanisms, the precise modulation of parameters like blood flow velocity or shear stress is centrally important. Questions related to blood flow have been addressed in the past in either embryonic or ex vivo-zebrafish models but little information is available for adult animals. Here we describe a pharmacological approach to modulate cardiac and hemodynamic parameters in adult zebrafish in vivo.Adult zebrafish were paralyzed and orally perfused with salt water. The drugs isoprenaline and sodium nitroprusside were directly applied with the perfusate, thus closely resembling the preferred method for drug delivery in zebrafish, namely within the water. Drug effects on the heart and on blood flow in the submental vein were studied using electrocardiograms, in vivo-microscopy and mathematical flow simulations.Under control conditions, heart rate, blood flow velocity and shear stress varied less than ± 5%. Maximal chronotropic effects of isoprenaline were achieved at a concentration of 50 μmol/L, where it increased the heart rate by 22.6 ± 1.3% (n = 4; p < 0.0001. Blood flow velocity and shear stress in the submental vein were not significantly increased. Sodium nitroprusside at 1 mmol/L did not alter the heart rate but increased blood flow velocity by 110.46 ± 19.64% (p = 0.01 and shear stress by 117.96 ± 23.65% (n = 9; p = 0.03.In this study, we demonstrate that cardiac and hemodynamic parameters in adult zebrafish can be efficiently modulated by isoprenaline and sodium nitroprusside. Together with the suitability of the zebrafish for in vivo-microscopy and genetic modifications, the methodology described permits studying biological processes that are dependent on hemodynamic alterations.

Hemodynamic Characteristics Including Pulmonary Hypertension at Rest and During Exercise Before and After Heart Transplantation

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Lundgren, Jakob; Rådegran, Göran

2015-01-01

Background Little is known about the hemodynamic response to exercise in heart failure patients at various ages before and after heart transplantation (HT). This information is important because postoperative hemodynamics may be a predictor of survival. To investigate the hemodynamic response to HT and exercise, we grouped our patients based on preoperative age and examined their hemodynamics at rest and during exercise before and after HT. Methods and Results Ninety-four patients were evaluated at rest prior to HT with right heart catheterization at our laboratory. Of these patients, 32 were evaluated during slight supine exercise before and 1 year after HT. Postoperative evaluations were performed at rest 1 week after HT and at rest and during exercise at 4 weeks, 3 months, 6 months, and 1 year after HT. The exercise patients were divided into 2 groups based on preoperative age of ≤50 or >50 years. There were no age-dependent differences in the preoperative hemodynamic exercise responses. Hemodynamics markedly improved at rest and during exercise at 1 and 4 weeks, respectively, after HT; however, pulmonary and, in particular, ventricular filling pressures remained high during exercise at 1 year after HT, resulting in normalized pulmonary vascular resistance response but deranged total pulmonary vascular resistance response. Conclusions Our findings suggest that, (1) in patients with heart failure age ≤50 or >50 years may not affect the hemodynamic response to exercise to the same extent as in healthy persons, and (2) total pulmonary vascular resistance may be more adequate than pulmonary vascular resistance for evaluating the exercise response after HT. PMID:26199230

Can Unstable Shoe Be Used As a Safety Training Shoe for Rehabilitation Exercises?

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Amin Gandomkar

2014-04-01

Full Text Available Objective: Unstable shoes have been recommended to osteoarthritis patients in order to reduce walking injuries. The aim of this study was to test the effect of unstable shoe on biomechanical selected variables related to injury during stanse phase of running. Materials & Methods: Twenty five healthy young male students available men (21±2.27years participated in this study. Subjects were asked to ran on the force plate in barefoot, with unstable and control shoe conditions. Active and passive joint power, peak anterior-posterior forces, active and passive vertical force, loading rate and impulse of posterior and passive vertical forces variables were recorded using synchronizing force plate and video camera and calculated in MATLAB software. A repeated measure of ANOVA used to test the hypothesis in SPSS software (version 20, p<0.05. Results: negative power at Ankle joint decreased significantly by 49%, 35% using unstable shoe compared to contol shoe and barefoot conditions respectively (P=0.02,P<0.05. Furthemore, unstable shoe decreased significantly the active ankle power compared to barefoot condition by 23% (P=0.01. Loading rate and peak of passive vertical force, impulse and peak of posterior force increased significantly in unstable shoe compared to control shoe (P<0.05. Conclusion: Unstable shoe increased some of running related injuries risk factors such as Loading rate and peak of passive vertical force, impulse and peak of posterior force. Furthemore, this shoe could decrease absorption potential shank muscles and ankle active stability compared to control shoe. However, with increase of ankle active power compared to barefoot and lower anterior force, Unstable shoe could improve the ankle joint force generation and propulsion potential.

Hemodynamic effects of microgravity and their ground-based simulations

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Lobachik, V. I.; Abrosimov, S. V.; Zhidkov, V. V.; Endeka, D. K.

Hemodynamic effects of simulated microgravity were investigated, in various experiments, using radioactive isotopes, in which 40 healthy men, aged 35 to 42 years, took part. Blood shifts were evaluated qualitatively and quantitatively. Simulation studies included bedrest, head-down tilt (-5° and -15°), and vertical water immersion, it was found that none of the methods could entirely simulate hemodynamic effects of microgravity. Subjective sensations varied in a wide range. They cannot be used to identify reliably the effects of real and simulated microgravity. Renal fluid excretion in real and simulated microgravity was different in terms of volume and time. The experiments yielded data about the general pattern of circulation with blood displaced to the upper body.

Use of lignocaine or nitroglycerine for blunting of hemodynamic stress response during electroconvulsive therapy

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Muhammad Umar Zahoor

2014-01-01

Conclusion: NTG provided more hemodynamic stability in post-ECT period as compared to lignocaine which only prevented a surge in HR without any effect on MAP. We conclude that NTG can safely be instituted for anaesthesia in ECT patients for prevention of hemodynamic stress response.

[Indicators of general, cerebral, and regional hemodynamics in myopic schoolchildren aged 13-15 years].

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Iastrebtseva, T A; Chuprov, A D; Plotnikova, Iu A

2002-01-01

110 schoolchildren aged 13-15 years were examined. 24 of them had pseudomyopia and 6 patients myopia of various forms. A control group consisted of 38 children. Central hemodynamics was estimated by average dynamic pressure, cerebral hemodynamics--by rheoencephalography, regional hemodynamics--by dopplerography of the internal carotid and suprapubic arteries. It was found that with myopia progression, the average dynamic pressure positively comes down with reduction of reographic waves amplitude in rheogram. The blood flow rate in internal carotid and suprapubic arteries has no substantial impact on myopia course. Predisposition to arterial hypotension is a risk factor for myopia development and progression.

Some hemodynamic changes in the organism following exposure to X-and gamma-radiation

Energy Technology Data Exchange (ETDEWEB)

Bliznakov, V; Mikhailov, A [Meditsinska Akademiya, Sofia (Bulgaria). Nauchen Inst. po Rentgenologiya i Radiobiologiya

1982-01-01

The hemodynamic response to dosed exercise of 705 physicians, nurses, roentgen technicians and hospital attendants, working with X-ray diagnostic and therapeutic devices, was studied. The doses received on professional irradiation proved to be below the threshold ones. A significantly increased incidence was recorded in cases of atonic hemodynamic response, mainly in medical workers, employed in X-ray departments.

Photoacoustic microscopy of cerebral hemodynamic and oxygen-metabolic responses to anesthetics

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Cao, Rui; Li, Jun; Ning, Bo; Sun, Naidi; Wang, Tianxiong; Zuo, Zhiyi; Hu, Song

2017-02-01

General anesthetics are known to have profound effects on cerebral hemodynamics and neuronal activities. However, it remains a challenge to directly assess anesthetics-induced hemodynamic and oxygen-metabolic changes from the true baseline under wakefulness at the microscopic level, due to the lack of an enabling technology for high-resolution functional imaging of the awake mouse brain. To address this challenge, we have developed head-restrained photoacoustic microscopy (PAM), which enables simultaneous imaging of the cerebrovascular anatomy, total concentration and oxygen saturation of hemoglobin (CHb and sO2), and blood flow in awake mice. From these hemodynamic measurements, two important metabolic parameters, oxygen extraction fraction (OEF) and the cerebral metabolic rate of oxygen (CMRO2), can be derived. Side-by-side comparison of the mouse brain under wakefulness and anesthesia revealed multifaceted cerebral responses to isoflurane, a volatile anesthetic widely used in preclinical research and clinical practice. Key observations include elevated cerebral blood flow (CBF) and reduced oxygen extraction and metabolism.

Singular system analysis of the Local Power Range Monitor (LPRM) readings of a Boiling Water Reactor (BWR) in an unstable event

International Nuclear Information System (INIS)

Ginestar Peiro, D.; Verdu, G.; Miro, R.

2006-01-01

Singular system analysis is a successful technique to separate oscillating components from a given signal. A methodology is proposed to apply this technique to the signals obtained from the LPRMs of a boiling water reactor core and extract the contributions of the in-phase oscillation and the out-of-phase oscillations from the LPRM readings during an unstable event. This methodology has been validated with synthetic signals and simulations of in-phase and out-of-phase oscillations of the Leibstadt reactor. Finally, one case of Ringhals I Stability Benchmark has been analysed. (author)

J-integral evaluation and stability analysis in the unstable ductile fracture

International Nuclear Information System (INIS)

Miyoshi, Toshiro; Yoshida, Yuichiro; Shiratori, Masaki.

1984-01-01

Concerning unstable ductile fracture, which is an important problem on the structural stability of line pipes, nuclear reactor piping and so on, the research on fracture mechanics parameters which control the beginning of the stable growth and unstable growth of cracks attracts interest. At present, as the parameters, the T-modulus based on J-integral crack tip opening angle, crack opening angle averaged over crack developing part, plastic work coefficient and so on have been proposed. The research on the effectiveness and inter-relation of these parameters is divided into generation phase and application phase, and by these researches, it was reported that all T-modulus, CTOA and COA took almost constant values in relation to crack development, except initial transition period. In order to decide which parameter is most appropriate, the detailed analysis is required. In this study, the analysis of unstable ductile fracture of a central crack test piece and a small tensile test piece was carried out by finite element method, and the evaluation of J-integral in relation to crack development, J-integral resistance value when COA is assumed to be a constant, the form of an unstable fracture occurring point and the compliance dependence were examined. The method of analysis, the evaluation of J-integral, J-integral resistance value, unstable fracture occurring point and stability diagram are described. (Kako, I.)

Accumulation of unstable periodic orbits and the stickiness in the two-dimensional piecewise linear map.

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Akaishi, A; Shudo, A

2009-12-01

We investigate the stickiness of the two-dimensional piecewise linear map with a family of marginal unstable periodic orbits (FMUPOs), and show that a series of unstable periodic orbits accumulating to FMUPOs plays a significant role to give rise to the power law correlation of trajectories. We can explicitly specify the sticky zone in which unstable periodic orbits whose stability increases algebraically exist, and find that there exists a hierarchy in accumulating periodic orbits. In particular, the periodic orbits with linearly increasing stability play the role of fundamental cycles as in the hyperbolic systems, which allows us to apply the method of cycle expansion. We also study the recurrence time distribution, especially discussing the position and size of the recurrence region. Following the definition adopted in one-dimensional maps, we show that the recurrence time distribution has an exponential part in the short time regime and an asymptotic power law part. The analysis on the crossover time T(c)(*) between these two regimes implies T(c)(*) approximately -log[micro(R)] where micro(R) denotes the area of the recurrence region.

Stabilization and analytical tuning rule of double-loop control scheme for unstable dead-time process

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Ugon, B.; Nandong, J.; Zang, Z.

2017-06-01

The presence of unstable dead-time systems in process plants often leads to a daunting challenge in the design of standard PID controllers, which are not only intended to provide close-loop stability but also to give good performance-robustness overall. In this paper, we conduct stability analysis on a double-loop control scheme based on the Routh-Hurwitz stability criteria. We propose to use this unstable double-loop control scheme which employs two P/PID controllers to control first-order or second-order unstable dead-time processes typically found in process industries. Based on the Routh-Hurwitz stability necessary and sufficient criteria, we establish several stability regions which enclose within them the P/PID parameter values that guarantee close-loop stability of the double-loop control scheme. A systematic tuning rule is developed for the purpose of obtaining the optimal P/PID parameter values within the established regions. The effectiveness of the proposed tuning rule is demonstrated using several numerical examples and the result are compared with some well-established tuning methods reported in the literature.

Decomposition of Near-Infrared Spectroscopy Signals Using Oblique Subspace Projections: Applications in Brain Hemodynamic Monitoring

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Alexander Caicedo

2016-11-01

Full Text Available Clinical data is comprised by a large number of synchronously collected biomedical signals that are measured at different locations. Deciphering the interrelationships of these signals can yield important information about their dependence providing some useful clinical diagnostic data. For instance, by computing the coupling between Near-Infrared Spectroscopy signals (NIRS and systemic variables the status of the hemodynamic regulation mechanisms can be assessed. In this paper we introduce an algorithm for the decomposition of NIRS signals into additive components. The algorithm, SIgnal DEcomposition base on Obliques Subspace Projections (SIDE-ObSP, assumes that the measured NIRS signal is a linear combination of the systemic measurements, following the linear regression model y = Ax + _. SIDE-ObSP decomposes the output such that, each component in the decomposition represents the sole linear influence of one corresponding regressor variable. This decomposition scheme aims at providing a better understanding of the relation between NIRS and systemic variables, and to provide a framework for the clinical interpretation of regression algorithms, thereby, facilitating their introduction into clinical practice. SIDE-ObSP combines oblique subspace projections (ObSP with the structure of a mean average system in order to define adequate signal subspaces. To guarantee smoothness in the estimated regression parameters, as observed in normal physiological processes, we impose a Tikhonov regularization using a matrix differential operator. We evaluate the performance of SIDE-ObSP by using a synthetic dataset, and present two case studies in the field of cerebral hemodynamics monitoring using NIRS. In addition, we compare the performance of this method with other system identification techniques. In the first case study data from 20 neonates during the first three days of life was used, here SIDE-ObSP decoupled the influence of changes in arterial oxygen

Decomposition of Near-Infrared Spectroscopy Signals Using Oblique Subspace Projections: Applications in Brain Hemodynamic Monitoring.

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Caicedo, Alexander; Varon, Carolina; Hunyadi, Borbala; Papademetriou, Maria; Tachtsidis, Ilias; Van Huffel, Sabine

2016-01-01

Clinical data is comprised by a large number of synchronously collected biomedical signals that are measured at different locations. Deciphering the interrelationships of these signals can yield important information about their dependence providing some useful clinical diagnostic data. For instance, by computing the coupling between Near-Infrared Spectroscopy signals (NIRS) and systemic variables the status of the hemodynamic regulation mechanisms can be assessed. In this paper we introduce an algorithm for the decomposition of NIRS signals into additive components. The algorithm, SIgnal DEcomposition base on Obliques Subspace Projections (SIDE-ObSP), assumes that the measured NIRS signal is a linear combination of the systemic measurements, following the linear regression model y = Ax + ϵ . SIDE-ObSP decomposes the output such that, each component in the decomposition represents the sole linear influence of one corresponding regressor variable. This decomposition scheme aims at providing a better understanding of the relation between NIRS and systemic variables, and to provide a framework for the clinical interpretation of regression algorithms, thereby, facilitating their introduction into clinical practice. SIDE-ObSP combines oblique subspace projections (ObSP) with the structure of a mean average system in order to define adequate signal subspaces. To guarantee smoothness in the estimated regression parameters, as observed in normal physiological processes, we impose a Tikhonov regularization using a matrix differential operator. We evaluate the performance of SIDE-ObSP by using a synthetic dataset, and present two case studies in the field of cerebral hemodynamics monitoring using NIRS. In addition, we compare the performance of this method with other system identification techniques. In the first case study data from 20 neonates during the first 3 days of life was used, here SIDE-ObSP decoupled the influence of changes in arterial oxygen saturation from the

Measurement of hemodynamics during postural changes using a new wearable cephalic laser blood flowmeter.

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Fujikawa, Tetsuya; Tochikubo, Osamu; Kura, Naoki; Kiyokura, Takanori; Shimada, Junichi; Umemura, Satoshi

2009-10-01

Patients with orthostatic hypotension have pathologic hemodynamics related to changes in body posture. A new cephalic laser blood flowmeter that can be worn on the tragus to investigate the hemodynamics upon rising from a sitting or squatting posture was developed. The relationship between cephalic hemodynamics and cerebral ischemic symptoms in 63 subjects in a sitting, squatting, and standing positions using the new device was evaluated. Transient decrease in blood pressure within 15 s after rising to an erect position possibly causes dizziness, syncope, and fall. Subjects exhibiting dizziness upon standing showed a significant decrease in the cephalic blood flow (CBF) and indirect beat-to-beat systolic blood pressure, as monitored by the Finometer, and a significant correlation was observed between the drop ratio (drop value on rising/mean value in the squatting position) of CBF and that of systolic blood pressure. This new wearable CBF-meter is potentially useful for estimating cephalic hemodynamics and objectively diagnosing cerebral ischemic symptoms of subjects in a standing posture.

Hemodynamics in stented vertebral artery ostial stenosis based on computational fluid dynamics simulations.

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Qiao, Aike; Dai, Xuan; Niu, Jing; Jiao, Liqun

2016-01-01

Hemodynamic factors may affect the potential occurrence of in-stent restenosis (ISR) after intervention procedure of vertebral artery ostial stenosis (VAOS). The purpose of the present study is to investigate the influence of stent protrusion length in implantation strategy on the local hemodynamics of the VAOS. CTA images of a 58-year-old female patient with posterior circulation transient ischemic attack were used to perform a 3D reconstruction of the vertebral artery. Five models of the vertebral artery before and after the stent implantation were established. Model 1 was without stent implantation, Model 2-5 was with stent protruding into the subclavian artery for 0, 1, 2, 3 mm, respectively. Computational fluid dynamics simulations based on finite element analysis were employed to mimic the blood flow in arteries and to assess hemodynamic conditions, particularly the blood flow velocity and wall shear stress (WSS). The WSS and the blood flow velocity at the vertebral artery ostium were reduced by 85.33 and 35.36% respectively after stents implantation. The phenomenon of helical flow disappeared. Hemodynamics comparison showed that stent struts that protruded 1 mm into the subclavian artery induced the least decrease in blood speed and WSS. The results suggest that stent implantation can improve the hemodynamics of VAOS, while stent struts that had protruded 1 mm into the subclavian artery would result in less thrombogenesis and neointimal hyperplasia and most likely decrease the risk of ISR.

The use of a mutationally unstable X-chromosome in Drosophila melanogaster for mutagenicity testing

International Nuclear Information System (INIS)

Rasmuson, B.; Svahlin, H.; Rasmuson, A.; Montell, I.; Olofsson, H.

1978-01-01

Somatic eye-colour mutations in an unstable genetic system, caused by a transposable element in the white locus of the X-chromosome in Drosophila melanogaster, is suggested as an assay system for mutagenicity testing. The system is evaluated by comparison with a corresponding system in a stable X-chromosome. Its sensitivity is confirmed with X-ray and EMS treatment, and it is found to be confined to the specific segment of the X-chromosome where the transposable element is localized. (Auth.)

Characterization of Unstable Rock Slopes Through Passive Seismic Measurements

Science.gov (United States)

Kleinbrod, U.; Burjanek, J.; Fäh, D.

2014-12-01

Catastrophic rock slope failures have high social impact, causing significant damage to infrastructure and many casualties throughout the world each year. Both detection and characterization of rock instabilities are therefore of key importance. An analysis of ambient vibrations of unstable rock slopes might be a new alternative to the already existing methods, e.g. geotechnical displacement measurements. Systematic measurements have been performed recently in Switzerland to study the seismic response of potential rockslides concerning a broad class of slope failure mechanisms and material conditions. Small aperture seismic arrays were deployed at sites of interest for a short period of time (several hours) in order to record ambient vibrations. Each measurement setup included a reference station, which was installed on a stable part close to the instability. Recorded ground motion is highly directional in the unstable parts of the rock slope, and significantly amplified with respect to stable areas. These effects are strongest at certain frequencies, which were identified as eigenfrequencies of the unstable rock mass. In most cases the directions of maximum amplification are perpendicular to open cracks and in good agreement with the deformation directions obtained by geodetic measurements. Such unique signatures might improve our understanding of slope structure and stability. Thus we link observed vibration characteristics with available results of detailed geological characterization. This is supported by numerical modeling of seismic wave propagation in fractured media with complex topography.For example, a potential relation between eigenfrequencies and unstable rock mass volume is investigated.

Characteristics of intraoperative abnormal hemodynamics during resection of an intra-fourth ventricular tumor located on the dorsal medulla oblongata.

Science.gov (United States)

Ideguchi, Makoto; Kajiwara, Koji; Yoshikawa, Koichi; Sadahiro, Hirokazu; Nomura, Sadahiro; Fujii, Masami; Suzuki, Michiyasu

2013-01-01

Abnormal hemodynamics during extirpation of a para-medulla oblongata (MO) tumor is common and may be associated with direct vagal stimulation of the medullary circuit. However, resection of tumors on the dorsal MO may also induce hemodynamic instability without direct vagal stimulus. The objective of this study was to examine the characteristics of hemodynamic instability unrelated to vagal stimulus during dissection of an intra-fourth ventricular tumor with attachment to the dorsal MO. A retrospective analysis was performed in 13 patients. Abnormal hemodynamics were defined as a > 20% change from the means of the intraoperative mean arterial pressure (MAP) and heart rate (HR). Relationships of intraoperative hemodynamics were evaluated with various parameters, including the volume of the MO. Six patients (46.2%) had intraoperative hypertension during separation of the tumor bulk from the dorsal MO. The maximum MAP and HR in these patients were significantly greater than those in patients with normal hemodynamics (116.0 ± 18.0 mmHg versus 85.6 ± 6.5 mmHg; 124.3 ± 22.8 bpm versus 90.5 ± 14.7 bpm). All six cases with abnormal hemodynamics showed hemodynamic fluctuation during separation of the tumor bulk from the dorsal MO. The preoperative volume of the MO in these patients was 1.11 cc less than that in patients with normal hemodynamics, but the volume after tumor resection was similar in the two groups (5.23 cc and 5.12 cc). This suggests that the MO was compressed by the conglutinate tumor bulk, with resultant fluctuation of hemodynamics. Recognition of and preparation for this phenomenon are important for surgery on a tumor located on the dorsal MO.

Unstable pigment mutants of Chlorella vulgaris B. as induced by UV irradiation

International Nuclear Information System (INIS)

Chankova, S.; Vinarova, K.

1987-01-01

The dynamics of arising of unstable 'segregating' pigment mutants of Chlorella vulgaris B. has been investigated in dependence on the dose of UV-rays applied and the macro- and microstructural changes taking place. The mutants are found to occur with a low frequency, irrespective of the dose applied and the presence or absence of photo-reactivation. A constantly recurring process of decomposition into two subclones is observed: light green (unstable) and yellow-green (stable). The existence of two cellular populations - structurally damaged and structurally undamaged - in the light-green unstable subclone has been demonstrated. There exists a qualitative and a quantitative correlation between the structural deformations in the cell and the dose with which the unstable pigment mutants are induced. Disturbances in the cell division are observed,resulting in delayed growth rate and the formation of small colonies

Differentiation of Constriction and Restriction: Complex Cardiovascular Hemodynamics.

Science.gov (United States)

Geske, Jeffrey B; Anavekar, Nandan S; Nishimura, Rick A; Oh, Jae K; Gersh, Bernard J

2016-11-29

Differentiation of constrictive pericarditis (CP) from restrictive cardiomyopathy (RCM) is a complex and often challenging process. Because CP is a potentially curable cause of heart failure and therapeutic options for RCM are limited, distinction of these 2 conditions is critical. Although different in regard to etiology, prognosis, and treatment, CP and RCM share a common clinical presentation of predominantly right-sided heart failure, in the absence of significant left ventricular systolic dysfunction or valve disease, due to impaired ventricular diastolic filling. Fundamental to the diagnosis of either condition is a clear understanding of the underlying hemodynamic principles and pathophysiology. We present a contemporary review of the pathophysiology, hemodynamics, diagnostic assessment, and therapeutic approach to patients presenting with CP and RCM. Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

A Novel Technique for Identifying Patients with ICU Needs Using Hemodynamic Features

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A. Jalali

2012-01-01

Full Text Available Identification of patients requiring intensive care is a critical issue in clinical treatment. The objective of this study is to develop a novel methodology using hemodynamic features for distinguishing such patients requiring intensive care from a group of healthy subjects. In this study, based on the hemodynamic features, subjects are divided into three groups: healthy, risky and patient. For each of the healthy and patient subjects, the evaluated features are based on the analysis of existing differences between hemodynamic variables: Blood Pressure and Heart Rate. Further, four criteria from the hemodynamic variables are introduced: circle criterion, estimation error criterion, Poincare plot deviation, and autonomic response delay criterion. For each of these criteria, three fuzzy membership functions are defined to distinguish patients from healthy subjects. Furthermore, based on the evaluated criteria, a scoring method is developed. In this scoring method membership degree of each subject is evaluated for the three classifying groups. Then, for each subject, the cumulative sum of membership degree of all four criteria is calculated. Finally, a given subject is classified with the group which has the largest cumulative sum. In summary, the scoring method results in 86% sensitivity, 94.8% positive predictive accuracy and 82.2% total accuracy.

Implant experience with an implantable hemodynamic monitor for the management of symptomatic heart failure.

Science.gov (United States)

Steinhaus, David; Reynolds, Dwight W; Gadler, Fredrik; Kay, G Neal; Hess, Mike F; Bennett, Tom

2005-08-01

Management of congestive heart failure is a serious public health problem. The use of implantable hemodynamic monitors (IHMs) may assist in this management by providing continuous ambulatory filling pressure status for optimal volume management. The Chronicle system includes an implanted monitor, a pressure sensor lead with passive fixation, an external pressure reference (EPR), and data retrieval and viewing components. The tip of the lead is placed near the right ventricular outflow tract to minimize risk of sensor tissue encapsulation. Implant technique and lead placement is similar to that of a permanent pacemaker. After the system had been successfully implanted in 148 patients, the type and frequency of implant-related adverse events were similar to a single-chamber pacemaker implant. R-wave amplitude was 15.2 +/- 6.7 mV and the pressure waveform signal was acceptable in all but two patients in whom presence of artifacts required lead repositioning. Implant procedure time was not influenced by experience, remaining constant throughout the study. Based on this evaluation, permanent placement of an IHM in symptomatic heart failure patients is technically feasible. Further investigation is warranted to evaluate the use of the continuous hemodynamic data in management of heart failure patients.

Technetium-99m-pyrophosphate myocardial imaging in unstable angina

International Nuclear Information System (INIS)

Willerson, J.T.; Parkey, R.W.; Lewis, S.E.; Buja, L.M.; Bonte, F.J.

1980-01-01

The authors have found that approximately one third of patients with the syndrome of unstable angina pectoris have abnormal 99mTc-pyrophosphate myocardial scintigrams even in the absence of abnormal enzymes and electrocardiographic confirmation of the presence of acute myocardial necrosis. Thus, 99mTc-pyrophosphate myocardial imaging technique appears to represent a sensitive means to detect acute multicellular injury associated with the clinical syndrome of unstable angina pectoris even when cardiac enzymes are normal and the electrocardiogram does not definitively document the presence of acute myocardial necrosis. (Auth.)

Race predictors and hemodynamic alteration after an ultra-trail marathon race

Directory of Open Access Journals (Sweden)

Taksaudom N

2017-10-01

Full Text Available Noppon Taksaudom,1 Natee Tongsiri,2 Amarit Potikul,1 Chawakorn Leampriboon,1 Apichat Tantraworasin,1 Anong Chaiyasri,1 1Cardiovascular and Thoracic Surgery Unit, Department of Surgery, Chiang Mai University Hospital, 2Department of Mathematics, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand Objective: Unique rough-terrain ultra-trail running races have increased in popularity. Concerns regarding the suitability of the candidates make it difficult for organizers to manage safety regulations. The purpose of this study was to identify possible race predictors and assess hemodynamic change after long endurance races.Methods: We studied 228 runners who competed in a 66 km-trail running race. A questionnaire and noninvasive hemodynamic flow assessment including blood pressure, heart rate, stroke volume, stroke volume variation, systemic vascular resistance, cardiac index, and oxygen saturation were used to determine physiologic alterations and to identify finish predictors. One hundred and thirty volunteers completed the questionnaire, 126 participants had a prerace hemodynamic assessment, and 33 of these participants completed a postrace assessment after crossing the finish line. The participants were divided into a finisher group and a nonfinisher group.Results: The average age of all runners was 37 years (range of 24–56 years. Of the 228 ­runners, 163 (71.5% were male. There were 189 (82.9% finishers. Univariable analysis indicated that the finish predictors included male gender, longest distance ever run, faster running records, and lower diastolic pressure. Only a lower diastolic pressure was a significant predictor of race finishing (diastolic blood pressure 74–84 mmHg: adjusted odd ratio 3.81; 95% confidence interval [CI]  =1.09–13.27 and diastolic blood pressure <74 mmHg: adjusted odd ratio 7.74; 95% CI =1.57–38.21 using the figure from the multivariable analysis. Among the finisher group, hemodynamic parameters

Morphologic and hemodynamic analysis of dental pulp in dogs after molar intrusion with the skeletal anchorage system.

Science.gov (United States)

Konno, Yuichi; Daimaruya, Takayoshi; Iikubo, Masahiro; Kanzaki, Reiko; Takahashi, Ichiro; Sugawara, Junji; Sasano, Takashi

2007-08-01

We have successfully treated skeletal open bite by intruding posterior teeth with the skeletal anchorage system. Our aim in this study was to morphologically and hemodynamically evaluate the changes in pulp tissues when molars are radically intruded. The mandibular fourth premolars of 9 adult beagle dogs were divided into 3 groups: a sham operated group (n = 6, 3 dogs), 4-month intrusion group (n = 6, 3 dogs), and a further 4-month retention group (n = 6, 3 dogs). We evaluated the morphological changes of the pulp and dentin-the amount of vacuolar degeneration in the odontoblast layer, the predentin width and nervous continuity in the pulp tissue, and the pulpal blood-flow response evoked by electrical stimulation in the dental pulp. Extreme molar intrusion with the skeletal anchorage system caused slight degenerative changes in the pulp tissue, followed by recovery after the orthodontic force was released. Circulatory system and nervous functions were basically maintained during the intrusion, although a certain level of downregulation was observed. These morphologic and functional regressive changes in the pulp tissue after molar intrusion improved during the retention period. Histologic changes and changes in pulpal blood flow and function are reversible, even during radical intrusion of molars.

A sliding mode observer for hemodynamic characterization under modeling uncertainties

KAUST Repository

Zayane, Chadia

2014-06-01

This paper addresses the case of physiological states reconstruction in a small region of the brain under modeling uncertainties. The misunderstood coupling between the cerebral blood volume and the oxygen extraction fraction has lead to a partial knowledge of the so-called balloon model describing the hemodynamic behavior of the brain. To overcome this difficulty, a High Order Sliding Mode observer is applied to the balloon system, where the unknown coupling is considered as an internal perturbation. The effectiveness of the proposed method is illustrated through a set of synthetic data that mimic fMRI experiments.

Endothelial cell impact on smooth muscle cell properties: role of hemodynamic forces

OpenAIRE

Killeen, Maria T.

2009-01-01

The vascular endothelium is a dynamic cell monolayer located at the interface of the vessel wall and bloodstream, where it regulates the physiological effects of humoral and hemodynamic stimuli on vessel tone and remodelling. Hemodynamic forces are of particular interest and include shear stress, the frictional force generated by blood as it drags against the endothelium, and cyclic strain, transmural pressure due to the pulsatile nature of blood flow. Both forces can profoundly modulate vasc...

Levosimendan reduces plasma B-type natriuretic peptide and interleukin 6, and improves central hemodynamics in severe heart failure patients.

Science.gov (United States)

Kyrzopoulos, Stamos; Adamopoulos, Stamatis; Parissis, John T; Rassias, John; Kostakis, George; Iliodromitis, Efstathios; Degiannis, Dimitrios; Kremastinos, Dimitrios Th

2005-03-30

Plasma B-type natriuretic peptide (BNP) and interleukin 6 (IL-6) levels have recently been demonstrated as significant neurohormonal markers associated with the progression of chronic heart failure (CHF). Additionally, clinical studies have shown that the calcium sensitizer, levosimendan, beneficially affects the central hemodynamics of CHF patients and improves their long-term prognosis. This study investigates whether levosimendan-induced hemodynamic improvement of CHF patients is related to the respective changes of NT-proBNP and IL-6 levels. Circulating levels of NT-pro BNP and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA) in 12 patients with decompensated advanced CHF at baseline, immediately after the end of a 24-h levosimendan infusion and 72 h after the initiation of treatment. Hemodynamic parameters of patients (pulmonary wedge and pulmonary artery pressure (PAP), systemic and pulmonary vascular resistance (PVR), stroke volume, and cardiac output and index) were also monitored during the same period. NT-proBNP and IL-6 levels were significantly reduced in severe CHF patients within 72 h after the initiation of levosimendan treatment (pNT-proBNP levels and the respective reduction of pulmonary wedge pressure (r(s)=0.65, pBNP and IL-6 levels may be useful biochemical markers related with the levosimendan-induced improvement in central hemodynamics and the clinical status of decompensated advanced CHF patients.

Non-invasive prediction of hemodynamically significant coronary artery stenoses by contrast density difference in coronary CT angiography

Energy Technology Data Exchange (ETDEWEB)

Hell, Michaela M., E-mail: michaela.hell@uk-erlangen.de [Department of Cardiology, University of Erlangen (Germany); Dey, Damini [Department of Biomedical Sciences, Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Taper Building, Room A238, 8700 Beverly Boulevard, Los Angeles, CA 90048 (United States); Marwan, Mohamed; Achenbach, Stephan; Schmid, Jasmin; Schuhbaeck, Annika [Department of Cardiology, University of Erlangen (Germany)

2015-08-15

Highlights: • Overestimation of coronary lesions by coronary computed tomography angiography and subsequent unnecessary invasive coronary angiography and revascularization is a concern. • Differences in plaque characteristics and contrast density difference between hemodynamically significant and non-significant stenoses, as defined by invasive fractional flow reserve, were assessed. • At a threshold of ≥24%, contrast density difference predicted hemodynamically significant lesions with a specificity of 75%, sensitivity of 33%, PPV of 35% and NPV of 73%. • The determination of contrast density difference required less time than transluminal attenuation gradient measurement. - Abstract: Objectives: Coronary computed tomography angiography (CTA) allows the detection of obstructive coronary artery disease. However, its ability to predict the hemodynamic significance of stenoses is limited. We assessed differences in plaque characteristics and contrast density difference between hemodynamically significant and non-significant stenoses, as defined by invasive fractional flow reserve (FFR). Methods: Lesion characteristics of 59 consecutive patients (72 lesions) in whom invasive FFR was performed in at least one coronary artery with moderate to high-grade stenoses in coronary CTA were evaluated by two experienced readers. Coronary CTA data sets were acquired on a second-generation dual-source CT scanner using retrospectively ECG-gated spiral acquisition or prospectively ECG-triggered axial acquisition mode. Plaque volume and composition (non-calcified, calcified), remodeling index as well as contrast density difference (defined as the percentage decline in luminal CT attenuation/cross-sectional area over the lesion) were assessed using a semi-automatic software tool (Autoplaq). Additionally, the transluminal attenuation gradient (defined as the linear regression coefficient between intraluminal CT attenuation and length from the ostium) was determined

Synthesis of unstable cyclic peroxides for chemiluminescence studies

Energy Technology Data Exchange (ETDEWEB)

Bartoloni, Fernando H.; Oliveira, Marcelo A. de; Augusto, Felipe A.; Ciscato, Luiz Francisco M.L.; Bastos, Erick L.; Baader, Wilhelm J., E-mail: wjbaader@iq.usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Quimica. Dept. de Quimica Fundamental

2012-11-15

Cyclic four-membered ring peroxides are important high-energy intermediates in a variety of chemi and bioluminescence transformations. Specifically, a-peroxy lactones (1,2-dioxetanones) have been considered as model systems for efficient firefly bioluminescence. However, the preparation of such highly unstable compounds is extremely difficult and, therefore, only few research groups have been able to study the properties of these substances. In this study, the synthesis, purification and characterization of three 1,2-dioxetanones are reported and a detailed procedure for the known synthesis of diphenoyl peroxide, another important model compound for the chemical generation of electronically excited states, is provided. For most of these peroxides, the complete spectroscopic characterization is reported here for the first time. (author)

Differential hemodynamic effects of exercise and volume expansion in people with and without heart failure

DEFF Research Database (Denmark)

Andersen, Mads Jønsson; Olson, Thomas P; Melenovsky, Vojtech

2015-01-01

BACKGROUND:Invasive hemodynamic exercise testing is commonly used in the evaluation of patients with suspected heart failure with preserved ejection fraction (HFpEF) or pulmonary hypertension. Saline loading has been suggested as an alternative provocative maneuver, but the hemodynamic changes...

Short-term vascular hemodynamic responses to isometric exercise in young adults and in the elderly

NARCIS (Netherlands)

Hartog, R. (Renee); D. Bolignano (Davide); E.J.G. Sijbrands (Eric); Pucci, G. (Giacomo); F.U.S. Mattace Raso (Francesco)

2018-01-01

textabstractBackground: Vascular aging is known to induce progressive stiffening of the large elastic arteries, altering vascular hemodynamics under both rest and stress conditions. In this study, we aimed to investigate changes in vascular hemodynamics in response to isometric handgrip exercise

Hemodynamic Effects of Phenylephrine, Vasopressin, and Epinephrine in Children With Pulmonary Hypertension: A Pilot Study.

Science.gov (United States)

Siehr, Stephanie L; Feinstein, Jeffrey A; Yang, Weiguang; Peng, Lynn F; Ogawa, Michelle T; Ramamoorthy, Chandra

2016-05-01

During a pulmonary hypertensive crisis, the marked increase in pulmonary vascular resistance can result in acute right ventricular failure and death. Currently, there are no therapeutic guidelines for managing an acute crisis. This pilot study examined the hemodynamic effects of phenylephrine, arginine vasopressin, and epinephrine in pediatric patients with pulmonary hypertension. In this prospective, open-label, nonrandomized pilot study, we enrolled pediatric patients previously diagnosed with pulmonary hypertensive who were scheduled electively for cardiac catheterization. Primary outcome was a change in the ratio of pulmonary-to-systemic vascular resistance. Baseline hemodynamic data were collected before and after the study drug was administered. Eleven of 15 participants were women, median age was 9.2 years (range, 1.7-14.9 yr), and median weight was 26.8 kg (range, 8.5-55.2 kg). Baseline mean pulmonary artery pressure was 49 ± 19 mm Hg, and mean indexed pulmonary vascular resistance was 10 ± 5.4 Wood units. Etiology of pulmonary hypertensive varied, and all were on systemic pulmonary hypertensive medications. Patients 1-5 received phenylephrine 1 μg/kg; patients 6-10 received arginine vasopressin 0.03 U/kg; and patients 11-15 received epinephrine 1 μg/kg. Hemodynamics was measured continuously for up to 10 minutes following study drug administration. After study drug administration, the ratio of pulmonary-to-systemic vascular resistance decreased in three of five patients receiving phenylephrine, five of five patients receiving arginine vasopressin, and three of five patients receiving epinephrine. Although all three medications resulted in an increase in aortic pressure, only arginine vasopressin consistently resulted in a decrease in the ratio of systolic pulmonary artery-to-aortic pressure. This prospective pilot study of phenylephrine, arginine vasopressin, and epinephrine in pediatric patients with pulmonary hypertensive showed an increase in aortic

Hemodynamic stroke: A rare pitfall in cranio cervical junction surgery

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Jan Frederick Cornelius

2014-01-01

Full Text Available Surgical C1C2-stabilization may be complicated by arterial-arterial embolism or arterial injury. Another potential complication is hemodynamic stroke. The latter might be induced in patients with poor posterior fossa collateralization (risk factor 1 when the vertebral artery (VA is compressed during reduction (risk factor 2. We report a clinical case where this rare situation occurred: A 72-year old patient was undergoing C1C2-stabilization for subluxation due to rheumatoid arthritis. Preoperative computed tomography angiography (CTA had shown poor collaterals in the posterior fossa. Furthermore, intraoperative Doppler ultrasound (US detected unilateral VA occlusion during reduction. It appeared to be a high-risk situation for hemodynamic stroke. Surgical inspection of the VA found osteofibrous compressing elements. Arterial decompression was performed resulting in the normal flow as detected by US. Subsequently, C1C2-stabilization could be realized. The clinical and radiological outcome was very favorable. In C1C2-stabilization precise analysis of preoperative CTA and intraoperative US are important to detect risk factors of hemodynamic stroke. Using these data may prevent this rare, but potentially life-threatening complication.

Time-Frequency Characterization of Cerebral Hemodynamics of Migraine Sufferers as Assessed by NIRS Signals

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Filippo Molinari

2010-01-01

Full Text Available Near-infrared spectroscopy (NIRS is a noninvasive system for the real-time monitoring of the concentration of oxygenated (O2Hb and reduced (HHb hemoglobin in the brain cortex. O2Hb and HHb concentrations vary in response to cerebral autoregulation. Sixty-eight women (14 migraineurs without aura, 49 migraineurs with aura, and 5 controls performed breath-holding and hyperventilation during NIRS recordings. Signals were processed using the Choi-Williams time-frequency transform in order to measure the power variation of the very-low frequencies (VLF: 20–40 mHz and of the low frequencies (LF: 40–140 mHz. Results showed that migraineurs without aura present different LF and VLF power levels than controls and migraineurs with aura. The accurate power measurement of the time-frequency analysis allowed for the discrimination of the subjects' hemodynamic patterns. The time-frequency analysis of NIRS signals can be used in clinical practice to assess cerebral hemodynamics.

Time-Frequency Characterization of Cerebral Hemodynamics of Migraine Sufferers as Assessed by NIRS Signals

Directory of Open Access Journals (Sweden)

Liboni William

2010-01-01

Full Text Available Abstract Near-infrared spectroscopy (NIRS is a noninvasive system for the real-time monitoring of the concentration of oxygenated ( and reduced (HHb hemoglobin in the brain cortex. and HHb concentrations vary in response to cerebral autoregulation. Sixty-eight women (14 migraineurs without aura, 49 migraineurs with aura, and 5 controls performed breath-holding and hyperventilation during NIRS recordings. Signals were processed using the Choi-Williams time-frequency transform in order to measure the power variation of the very-low frequencies (VLF: 20–40 mHz and of the low frequencies (LF: 40–140 mHz. Results showed that migraineurs without aura present different LF and VLF power levels than controls and migraineurs with aura. The accurate power measurement of the time-frequency analysis allowed for the discrimination of the subjects' hemodynamic patterns. The time-frequency analysis of NIRS signals can be used in clinical practice to assess cerebral hemodynamics.

Assessing the impact of sinus-saving modifications of carotid endarterectomy on autonomic regulation and central hemodynamics

Directory of Open Access Journals (Sweden)

А. А. Фокин

2016-03-01

Full Text Available BackgroundSuch complications as myocardial infarction, hyperperfusion syndrome and its effects, postoperative hematomes constitute a life-threatening event during early follow-up of carotid surgery. One of the main risk factors for these complications is a variation of central hemodynamics, especially that leading to arterial hypertension.ObjectiveThe study aimed to evaluate the safety of carotid sinus surgery as a way of preventing arterial hypertension after carotid artery reconstructions. The other objective was to compare the resultant data with the heart rate variations obtained during rhythmocardiography.MethodsThe study focused on central hemodynamics indicators and included 290 cases. All patients were broken down in two groups. 167 patients of the first group underwent dissection of carotid sinus nerves. The carotid sinus nerves of patients from the second group (123 patients were kept intact. Analysis of autonomic regulation of 13 patients from the first group and 17 patients from the other one was then carried out, with the heart rate variations accurately estimated at the neurocardiological laboratory.ResultsOn the first postoperative day all hemodynamic indicators (such as SBP, DBP, pulse pressure, heart rate in the second group were lower than those in the first group of patients (p<0.05, while tending to recover by the third day. This fact kept postoperative complications to a minimum. The patients from the second group also demonstrated a lower activity of the sympathetic nervous system and a higher activity of the parasympathetic one. These results explain the difference between the central hemodynamic indicators in two groups.ConclusionCarotid sinus-saving surgery decreases the risk of early postoperative complications caused by arterial hypertension. 

Comparison of hemodynamics during hyperthermal immersion and exercise testing in apparently healthy females aged 50-60 years.

Science.gov (United States)

Lietava, Jan; Vohnout, Branislav; Valent, Denis; Celko, Juraj

2004-07-01

Owing to excessive worries regarding adverse cardiac events, hyperthermal balneotherapy for patients with coronary artery disease is underprescribed. However, very few cardiac events occur in similar heat stress during Finnish sauna bathing. Exercise testing has proven to be a safe diagnostic procedure even in survivors of myocardial infarction. We compared the effects of hyperthermal immersion and exercise testing on cardiac hemodynamics in 21 apparently healthy women aged 50-60 years. The maximal symptom-limited bicycle exercise test was performed according to the modified protocol of Wasserman. Hyperthermal immersion was carried out in 40 degrees C water and was completed by increasing the core temperature by about 2 degrees C. The left ventricular function was evaluated using continuous measurement of thoracic electric bioimpedance during both tests. The blood pressure, index of contractility and heart rate were measured directly, whereas the cardiac index, left cardiac work index and systemic vascular resistance index were calculated. The hemodynamic response, as assessed at continuous non-invasive monitoring, showed substantial differences between hyperthermal immersion and exercise testing. Overall, we found a significantly lower hemodynamic load during hyperthermal immersion in comparison with exercise testing. Entering the bath, there was a significant decrease in the left cardiac work, contractility and blood pressure. We recorded a slight increase in the heart rate towards peak hyperthermal immersion. However, other modulators such as the mean arterial pressure, index of contractility, cardiac index and left cardiac work index decreased even below resting values. Excessive hyperthermal immersion induced a lower hemodynamic load in apparently healthy women than standard maximal exercise testing.

Ionizing radiation occupational exposure in the hemodynamics services; Exposicao ocupacional as radiacoes ionizantes nos servicos de hemodinamica

Energy Technology Data Exchange (ETDEWEB)

Gronchi, Claudia Carla

2004-07-01

The purpose of this research is to study the ionizing radiation occupational exposure in the hemodynamic services of two large scale hospitals (Hospital A and Hospital B) of the Sao Paulo city. The research looked into annual doses that 279 professionals of the hemodynamic services were exposed to between 1991 and 2002. The data analyzed was collected from the database of the Instituto de Pesquisas Energeticas e Nucleares (IPEN) for Hospital A, and from the Radiological Protection Department of Hospital B. Besides this, measures of hands and crystalline lens equivalent doses were performed during hemodynamic procedures of the physicians, assistant physicians and nursing assistants with TL dosimeters (CaSO{sub 4}:Dy + Teflon R) produced at IPEN. The safety procedures adopted by the hospitals were verified with the aid of a specific questionnaire for the hemodynamic services. Finally, a profile of the professionals that work in cardiac catheterism laboratories of the hemodynamic services was delineated, considering the variables of individual monitoring time, age and sex. This study allowed for observation of the behavior of the professionals' annual doses of these hemodynamic services in relation to the Comissao Nacional de Energia Nuclear and the Secretaria de Vigilancia Sanitaria limits. It showed that the annual doses of the same specialized occupations would vary from one hospital to another. It further showed the need of individual monitoring of the physicians' unprotected body parts (hands and crystalline lens) during the hemodynamic procedures. (author)

Is there a specific hemodynamic effect in reflexology? A systematic review of randomized controlled trials.

Science.gov (United States)

Jones, Jenny; Thomson, Patricia; Irvine, Kathleen; Leslie, Stephen J

2013-04-01

Reflexology claims that the feet are representative of the body and that massage to specific points of the feet increases blood supply to "mapped" organs in the body. This review provides the first systematic evaluation of existing reflexology randomized controlled trials (RCTs) to determine whether there is any evidence to suggest the existence of a reflexology treatment-related hemodynamic effect; to examine whether reflexology researchers used study designs that systematically controlled for nonspecific effects in order to isolate this specific component; and to highlight some of the methodological challenges that need to be overcome to demonstrate specific and beneficial hemodynamic effects. Fifty-two RCTs of reflexology published from 1990 to September 2011 were initially retrieved. Cardiorespiratory Department, Highland Heartbeat Centre, Raigmore Hospital, Inverness. Adult subjects. Studies using reflexology foot massage techniques as the intervention versus sham reflexology treatment, simple foot massage, conventional treatment, or no treatment as the control were then selected. OUTCOME MEASURES included any hemodynamic parameter potentially involved in the regulation of circulating blood volume and flow, including heart rate and systolic and diastolic arterial blood pressure. Seven RCTs suggested that reflexology has an effect on selected cardiovascular parameters; however, five of these delivered the reflexology intervention as a whole complex treatment, with the data collector often delivering the intervention themselves. This systematic review found that although reflexology has been shown to have an effect on selected hemodynamic variables, the lack of methodological control for nonspecific general massage effects means that there is little convincing evidence at this time to suggest the existence of a specific treatment-related hemodynamic effect. Furthermore, the review found that few studies of reflexology controlled for nonspecific effects in order

Collateral circulation alters downstream hemodynamic stress caused by intracranial atherosclerotic stenosis.

Science.gov (United States)

Liu, Xin; Dornbos, David; Pu, Yuehua; Leng, Xinyi; Song, Ligang; Jia, Baixue; Pan, Yuesong; Wang, David; Miao, Zhongrong; Wang, Yilong; Liu, Liping; Wang, Yongjun

2017-06-01

Fractional flow reserve (FFR) accurately predicts the degree of stenosis and is now widely used to identify clinically significant severe coronary artery lesions. In the current study, we utilized a similar indicator, fractional flow (FF), to determine the hemodynamic impact of symptomatic intracranial atherosclerotic stenosis (ICAS) and to assess the correlation of FF with the severity of stenosis and collateral circulation. Patients with symptomatic ICAS (70-99% stenosis) confirmed on digital subtraction angiography (DSA) were consecutively recruited. FF was obtained during DSA examination with the use of pressure sensors and was measured as a ratio, comparing measurements distal to an ICAS lesion (Pd) and within the aorta (Pa). The degree of leptomeningeal collateralization was graded from zero (absent) to four (complete compensatory). The correlation between FF, anatomical stenosis, and collateral status was then analyzed. Twenty-five patients with a mean age of 55.6 years were analyzed. The median percentage of stenosis and median FF were 82.3 and 0.68%, respectively. Eleven patients were found to have poor collateralization (grade 0-2), and fourteen patients were identified with good collateral circulation (grade 3-4). Overall, the hemodynamic impact of an atherosclerotic lesions worsened (decreased FF) as the percentage of stenosis increased, although this did not reach statistical significance (r = -0.398, p = 0.06). However, the status of collateralization significantly altered this correlation, worsening the hemodynamic impact in patients with poor collateral circulation (r = -0.677, p = 0.032). There was no difference in patients with good collateral circulation (r = -0.279, p = 0.356). An anatomically severe (70-99%) symptomatic ICAS lesion may generate significant hemodynamic stress downstream as assessed by the indicator FF, particularly in patients with poor collateral circulation. Further, good collateralization may mitigate this

Effects of pleural effusion drainage on oxygenation, respiratory mechanics, and hemodynamics in mechanically ventilated patients.

Science.gov (United States)

Razazi, Keyvan; Thille, Arnaud W; Carteaux, Guillaume; Beji, Olfa; Brun-Buisson, Christian; Brochard, Laurent; Mekontso Dessap, Armand

2014-09-01

In mechanically ventilated patients, the effect of draining pleural effusion on oxygenation is controversial. We investigated the effect of large pleural effusion drainage on oxygenation, respiratory function (including lung volumes), and hemodynamics in mechanically ventilated patients after ultrasound-guided drainage. Arterial blood gases, respiratory mechanics (airway, pleural and transpulmonary pressures, end-expiratory lung volume, respiratory system compliance and resistance), and hemodynamics (blood pressure, heart rate, and cardiac output) were recorded before and at 3 and 24 hours (H24) after pleural drainage. The respiratory settings were kept identical during the study period. The mean volume of effusion drained was 1,579 ± 684 ml at H24. Uncomplicated pneumothorax occurred in two patients. Respiratory mechanics significantly improved after drainage, with a decrease in plateau pressure and a large increase in end-expiratory transpulmonary pressure. Respiratory system compliance, end-expiratory lung volume, and PaO2/FiO2 ratio all improved. Hemodynamics were not influenced by drainage. Improvement in the PaO2/FiO2 ratio from baseline to H24 was positively correlated with the increase in end-expiratory lung volume during the same time frame (r = 0.52, P = 0.033), but not with drained volume. A high value of pleural pressure or a highly negative transpulmonary pressure at baseline predicted limited lung expansion following effusion drainage. A lesser improvement in oxygenation occurred in patients with ARDS. Drainage of large (≥500 ml) pleural effusion in mechanically ventilated patients improves oxygenation and end-expiratory lung volume. Oxygenation improvement correlated with an increase in lung volume and a decrease in transpulmonary pressure, but was less so in patients with ARDS.

Impact of Diversity of Morphological Characteristics and Reynolds number on Local Hemodynamics in Basilar Aneurysms

DEFF Research Database (Denmark)

Rafat, Marjan; Dabagh, Mahsa; Heller, Martin

2018-01-01

management. Existing aneurysm hemodynamics studies generally evaluate limited geometries or Reynolds numbers (Re), which are difficult to apply to a wide range of patient-specific cases. We focused on the association between hemodynamic characteristics and morphology. We assessed several two-dimensional (2D...

Journal of Clinical Monitoring and Computing 2015 end of year summary : cardiovascular and hemodynamic monitoring

NARCIS (Netherlands)

Bendjelid, Karim; Rex, Steffen; Scheeren, Thomas; Saugel, Bernd

Hemodynamic monitoring is essential in critically ill patients. In this regard, the Journal of Clinical Monitoring and Computing (JCMC) has become an ideal platform for publishing cardiovascular and hemodynamic monitoring-related research, as reflected by an increasing number of articles related to

Short separation regression improves statistical significance and better localizes the hemodynamic response obtained by near-infrared spectroscopy for tasks with differing autonomic responses.

Science.gov (United States)

Yücel, Meryem A; Selb, Juliette; Aasted, Christopher M; Petkov, Mike P; Becerra, Lino; Borsook, David; Boas, David A

2015-07-01

Autonomic nervous system response is known to be highly task-dependent. The sensitivity of near-infrared spectroscopy (NIRS) measurements to superficial layers, particularly to the scalp, makes it highly susceptible to systemic physiological changes. Thus, one critical step in NIRS data processing is to remove the contribution of superficial layers to the NIRS signal and to obtain the actual brain response. This can be achieved using short separation channels that are sensitive only to the hemodynamics in the scalp. We investigated the contribution of hemodynamic fluctuations due to autonomous nervous system activation during various tasks. Our results provide clear demonstrations of the critical role of using short separation channels in NIRS measurements to disentangle differing autonomic responses from the brain activation signal of interest.

Robust Output Model Predictive Control of an Unstable Rijke Tube

Directory of Open Access Journals (Sweden)

Fabian Jarmolowitz

2012-01-01

Full Text Available This work investigates the active control of an unstable Rijke tube using robust output model predictive control (RMPC. As internal model a polytopic linear system with constraints is assumed to account for uncertainties. For guaranteed stability, a linear state feedback controller is designed using linear matrix inequalities and used within a feedback formulation of the model predictive controller. For state estimation a robust gain-scheduled observer is developed. It is shown that the proposed RMPC ensures robust stability under constraints over the considered operating range.

Physiological basis of clinically used coronary hemodynamic indices

NARCIS (Netherlands)

Spaan, Jos A. E.; Piek, Jan J.; Hoffman, Julien I. E.; Siebes, Maria

2006-01-01

In deriving clinically used hemodynamic indices such as fractional flow reserve and coronary flow velocity reserve, simplified models of the coronary circulation are used. In particular, myocardial resistance is assumed to be independent of factors such as heart contraction and driving pressure.

Scaling Laws for Unstable Interfaces Driven by Strong Shocks in Cylindrical Geometry

International Nuclear Information System (INIS)

Zhang, Q.; Graham, M.J.; Graham, M.J.

1997-01-01

The Richtmyer-Meshkov (RM) instability is an interfacial interface between two fluids of different densities driven by shock waves and plays an important role in the studies of inertial confinement fusion and of supernovas. So far, most of the studies are for RM unstable interfaces driven by weak or intermediate shocks in planar geometry. For experiments conducted at the Nova laser, the unstable material interface is accelerated by very strong shocks. In this Letter, we present scaling laws for the RM unstable interface driven by strong imploding and exploding shocks. copyright 1997 The American Physical Society

Disorders of cardiac hemodynamic in attack period of bronchial asthma in children

Directory of Open Access Journals (Sweden)

Kondratiev V.А.

2016-05-01

Full Text Available By dopplerechocardiography method there was studied functional state of cardiac ventricles and character of hemodynamic disorders in 48 patients aged 5-17 years in attack period of moderately-severe and severe bronchial asthma. Group of comparison included 40 healthy peers. Disorders of central and peripheral hemodynamic in attack period of bronchial asthma in children were accompanied both by systolic and diastolic dysfunction of the left and right heart ventricles, herewith right ventricle was functioning in the mode of hyperdynamic, and left one – in the mode of hypodynamic. Combined systolic-diastolic variant of dysfunction both of right and left ventricles was developing in 58,3% of patients with moderately-severe and in 91,6% of patients with severe bronchial asthma. In the attack period of bronchial asthma in children equal directionality of systolic and diastolic dysfunction of heart ventricles was developing; this was characterized by synchronization of their function. Assessment of functional interaction of the ventricles under conditions of severe asthma attack showed direct and high (r=0,67 correlative interaction between finding of Tei index of the left and right ventricles, which characterize their systolic function; this, under conditions of increased hemodynamic pre-loading testified to compensatory increase of systolic interaction of ventricles. Direct and high (r=0,69 correlative interaction between time indices of isovolumic relaxation of the left and right ventricles, characterizing their diastolic function, testified to compensatory increase of diastolic interaction of ventricles under conditions of increase of hemodynamic post-loading. Imbalance of central and peripheral link of hemodynamic in attack period of bronchial asthma in children testified to development of cardiac insufficiency, which was compensated predominantly at the expense of increase of heart contractions rate.

Hemodynamic effects of rapid and slow infusions of manganese chloride and gadolinium-DTPA in dogs

International Nuclear Information System (INIS)

Slutsky, R.A.; Peterson, T.; Strich, G.; Brown, J.J.

1985-01-01

The acute hemodynamic effects of two paramagnetic contrast materials, manganese chloride and gadolinium-DTPA, were examined in dogs using ultrasonic dimension gauge crystals. Slow infusions (more than 15 minutes) of MnCl 2 or Gd-DTPA via an infusion pump had no significant hemodynamic effects. When given in just over 1 minute, Gd-DTPA produced elevated left ventricular (LV) end diastolic pressure and minor dilation of the ventricle and slowed diastolic filling. MnCl 2 , given rapidly, reduced systemic vascular resistance, resulting in hypotension. With both agents, these side effects waned after 5-10 minutes. It is concluded that both Gd-DTPA and MnCl 2 can be given safely in 0.1-mm/kg doses when administered as a slow, continuous infusion. Slow, intravenous infusion of Gd-DTPA or MnCl 2 is likely to be tolerated well by even severely ill individuals

Hemodynamics in diabetic orthostatic hypotension

DEFF Research Database (Denmark)

Hilsted, J; Parving, H H; Christensen, N J

1981-01-01

Hemodynamic variables (blood pressure, cardiac output, heart rate, plasma volume, splanchnic blood flow, and peripheral subcutaneous blood flow) and plasma concentrations of norepinephrine, epinephrine, and renin were measured in the supine position and after 30 min of quiet standing. This was done...... in normal subjects (n = 7) and in juvenile-onset diabetic patients without neuropathy (n = 8), with slight neuropathy (decreased beat-to-beat variation in heart rate during hyperventilation) (n = 8), and with severe neuropathy including orthostatic hypotension (n = 7). Blood pressure decreased precipitously...

Hemodynamic measurements in rat brain and human muscle using diffuse near-infrared absorption and correlation spectroscopies

Science.gov (United States)

Yu, Guoqiang; Durduran, Turgut; Furuya, D.; Lech, G.; Zhou, Chao; Chance, Britten; Greenberg, J. H.; Yodh, Arjun G.

2003-07-01

Measurement of concentration, oxygenation, and flow characteristics of blood cells can reveal information about tissue metabolism and functional heterogeneity. An improved multifunctional hybrid system has been built on the basis of our previous hybrid instrument that combines two near-infrared diffuse optical techniques to simultaneously monitor the changes of blood flow, total hemoglobin concentration (THC) and blood oxygen saturation (StO2). Diffuse correlation spectroscopy (DCS) monitors blood flow (BF) by measuring the optical phase shifts caused by moving blood cells, while diffuse photon density wave spectroscopy (DPDW) measures tissue absorption and scattering. Higher spatial resolution, higher data acquisition rate and higher dynamic range of the improved system allow us to monitor rapid hemodynamic changes in rat brain and human muscles. We have designed two probes with different source-detector pairs and different separations for the two types of experiments. A unique non-contact probe mounted on the back of a camera, which allows continuous measurements without altering the blood flow, was employed to in vivo monitor the metabolic responses in rat brain during KCl induced cortical spreading depression (CSD). A contact probe was used to measure changes of blood flow and oxygenation in human muscle during and after cuff occlusion or exercise, where the non-contact probe is not appropriate for monitoring the moving target. The experimental results indicate that our multifunctional hybrid system is capable of in vivo and non-invasive monitoring of the hemodynamic changes in different tissues (smaller tissues in rat brain, larger tissues in human muscle) under different conditions (static versus moving). The time series images of flow during CSD obtained by our technique revealed spatial and temporal hemodynamic changes in rat brain. Two to three fold longer recovery times of flow and oxygenation after cuff occlusion or exercise from calf flexors in a

Year in review in journal of clinical monitoring and computing 2014 : cardiovascular and hemodynamic monitoring

NARCIS (Netherlands)

Bendjelid, Karim; Rex, Steffen; Scheeren, Thomas; Critchley, Lester

Hemodynamic instability is a common sign in critically ill patients and its importance has been increasingly recognized during the last 20 years. Indeed, It is now appreciated that an adequate hemodynamic monitoring associated to reactive vigorous therapy is able to decrease the present ominous

Estimation of equivalent dose on the ends of hemodynamic physicians during neurological procedures

International Nuclear Information System (INIS)

Squair, Peterson L.; Souza, Luiz C. de; Oliveira, Paulo Marcio C. de

2005-01-01

The estimation of doses in the hands of physicists during hemodynamic procedures is important to verify the application of radiation protection related to the optimization and limit of dose, principles required by the Portaria 453/98 of Ministry of Health/ANVISA, Brazil. It was checked the levels of exposure of the hands of doctors during the use of the equipment in hemodynamic neurological procedures through dosimetric rings with thermoluminescent dosemeters detectors of LiF: Mg, Ti (TLD-100), calibrated in personal Dose equivalent HP (0.07). The average equivalent dose in the end obtained was 41.12. μSv per scan with an expanded uncertainty of 20% for k = 2. This value is relative to the hemodynamic Neurology procedure using radiological protection procedures accessible to minimize the dose

Hemodynamic and morphological characteristics of unruptured posterior communicating artery aneurysms with oculomotor nerve palsy.

Science.gov (United States)

Lv, Nan; Yu, Ying; Xu, Jinyu; Karmonik, Christof; Liu, Jianmin; Huang, Qinghai

2016-08-01

OBJECT Unruptured posterior communicating artery (PCoA) aneurysms with oculomotor nerve palsy (ONP) have a very high risk of rupture. This study investigated the hemodynamic and morphological characteristics of intracranial aneurysms with high rupture risk by analyzing PCoA aneurysms with ONP. METHODS Fourteen unruptured PCoA aneurysms with ONP, 33 ruptured PCoA aneurysms, and 21 asymptomatic unruptured PCoA aneurysms were included in this study. The clinical, morphological, and hemodynamic characteristics were compared among the different groups. RESULTS The clinical characteristics did not differ among the 3 groups (p > 0.05), whereas the morphological and hemodynamic analyses showed that size, aspect ratio, size ratio, undulation index, nonsphericity index, ellipticity index, normalized wall shear stress (WSS), and percentage of low WSS area differed significantly (p PCoA aneurysms with ONP demonstrated a distinctive morphological-hemodynamic pattern that was significantly different compared with asymptomatic unruptured PCoA aneurysms and was similar to ruptured PCoA aneurysms. The larger size, more irregular shape, and lower WSS might be related to the high rupture risk of PCoA aneurysms.

HEMODYNAMIC AND LACTIC ACID RESPONSES TO PROPRIOCEPTIVE NEUROMUSCULAR FACILITATION EXERCISE

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Zuhal Gültekin

2006-09-01

Full Text Available The hemodynamic and metabolic responses to proprioceptive neuromuscular facilitation (PNF exercise were examined in 32 male university students (aged 19-28 years. Ten repetitions of PNF exercises were applied to the subjects' dominant upper extremities in the following order: as an agonist pattern flexion, adduction and external rotation; and as an antagonist pattern extension, abduction and internal rotation. Heart rate (HR, systolic blood pressure (SBP, diastolic blood pressure (DBP, double product (DP, and blood lactate concentration (La were determined before, immediately after, and at 1st, 3rd, and 5th minutes after PNF exercise. A one-way ANOVA with repeated measures indicated significant differences in HR, SBP, DBP, DP and La immediately after PNF exercise. HR increased from 81 (±10 to 108 (±15 b·min-1 (p < 0.01, SBP increased from 117 (±10 to 125 (±11 mmHg (p < 0.01, DBP increased from 71 (±10 to 75 (±8 mmHg (p < 0.01, DP increased from 96 (±16 to 135 (±24 (p < 0.01, and La increased from 0.69 (±0.31 to 3.99 (±14.63 mmol·L-1 (p < 0.01. Thus PNF exercise resulted in increased hemodynamic responses and blood lactate concentration that indicate a high strain on the cardiovascular system and anaerobic metabolism in healthy subjects

Wear Behavior of an Unstable Knee: Stabilization via Implant Design?

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Jörn Reinders

2014-01-01

Full Text Available Background. Wear-related failures and instabilities are frequent failure mechanisms of total knee replacements. High-conforming designs may provide additional stability for the joint. This study analyzes the effects of a ligamentous insufficiency on the stability and the wear behavior of a high-conforming knee design. Methods. Two simulator wear tests were performed on a high-conforming total knee replacement design. In the first, a ligamentous-stable knee replacement with a sacrificed anterior cruciate ligament was simulated. In the second, a ligamentous-unstable knee with additionally insufficient posterior cruciate ligament and medial collateral ligament was simulated. Wear was determined gravimetrically and wear particles were analyzed. Implant kinematics was recorded during simulation. Results. Significantly higher wear rates (P≤0.001 were observed for the unstable knee (14.58±0.56 mg/106 cycles compared to the stable knee (7.97 ± 0.87 mg/106 cycles. A higher number of wear particles with only small differences in wear particle characteristics were observed. Under unstable knee conditions, kinematics increased significantly for translations and rotations (P≤0.01. This increase was mainly attributed to higher tibial posterior translation and internal rotations. Conclusion. Higher kinematics under unstable test conditions is a result of insufficient stabilization via implant design. Due to the higher kinematics, increased wear was observed in this study.

gamma. -unstable nuclei in the sdg boson model

Energy Technology Data Exchange (ETDEWEB)

Kuyucak, S.; Lac, V.S.; Morrison, I.; Barrett, B.R. (School of Physics, Univ. of Melbourne, Parkville (Australia))

1991-07-18

Following the recent Pt(p, p') experiments which indicated the need for g bosons to reproduce the E4 data, we have extended the O(6) limit of the sd boson model to include g bosons. It is shown that a {gamma}-unstable hamiltonian in the sdg model consisting of a quadrupole interaction and a g boson energy leads to results that are very similar to the O(6) limit. Deviations from the empirical energy spectrum that stem from the {gamma}-unstable nature of the hamiltonian can be improved by including a consistent hexadecapole interaction which induces triaxiality. The same hexadecapole operator can also account for the strong E4 transitions. Applications are made to the Xe and Pt isotopes. (orig.).

γ-unstable nuclei in the sdg boson model

Science.gov (United States)

Kuyucak, S.; Lac, V.-S.; Morrison, I.; Barrett, B. R.

1991-07-01

Following the recent Pt(p, p‧) experiments which indicated the need for g bosons to reproduce the E4 data, we have extended the O(6) limit of the sd boson model to include g bosons. It is shown that a γ-unstable hamiltonian in the sdg model consisting of a quadrupole interaction and a g boson energy leads to results that are very similar to the O(6) limit. Deviations from the empirical energy spectrum that stem from the γ-unstable nature of the hamiltonian can be improved by including a consistent hexadecapole interaction which induces triaxiality. The same hexadecapole operator can also account for the strong E4 transitions. Applications are made to the Xe and Pt isotopes.

Impact of tubing length on hemodynamics in a simulated neonatal extracorporeal life support circuit.

Science.gov (United States)

Qiu, Feng; Uluer, Mehmet C; Kunselman, Allen; Clark, J Brian; Myers, John L; Undar, Akif

2010-11-01

During extracorporeal life support (ECLS), a large portion of the hemodynamic energy is lost to various components of the circuit. Minimization of this loss in the circuit leads to better vital organ perfusion and decreases the risk of systemic inflammation. In this study, we evaluated the hemodynamic properties of differing lengths of tubing in a simulated neonatal ECLS circuit. The neonatal ECLS circuit used in this study included a Capiox Baby RX05 oxygenator (Terumo Corporation, Tokyo, Japan), a Rotaflow centrifugal pump (MAQUET Cardiopulmonary AG, Hirrlingen, Germany), and a heater and cooler unit. An 8Fr Biomedicus arterial and a 10Fr Biomedicus venous cannula were connected to the pseudopatient. One-fourth inch tubing was used for both the arterial and the venous line. A Hoffman clamp was located upstream from the pseudopatient to maintain a certain patient pressure. Three pressure transducers were placed at different sites: postoxygenator, prearterial cannula, and postarterial cannula. The system was primed with Lactated Ringer's solution; human blood was then added to maintain a hematocrit of 40%. The volume of the pseudopatient was 500mL. We hemodynamically evaluated three circuits with different lengths of tubing: 6, 4, and 2 feet (182.88, 121.92, and 60.96 cm, respectively) for both arterial and venous lines; the priming volumes including all of the components of the circuits were 195, 155, and 115mL, respectively. In each circuit, we measured the pressure drops of the arterial tubing and the arterial cannula, as well as the flow rates at different rpm (1750-3000, 250 intervals) under three patient pressures (40, 60, and 80mm Hg). All the experiments were conducted at 37°C. The pressure drop across the arterial cannula is much larger than that of arterial tubing in all set-ups, especially under high flow rates. Upon cutting the tubing from 6 to 2 feet, the pressure drop of the arterial tubing decreased by half, while the pressure drop of the arterial

The hemodynamic basis of exercise intolerance in tricuspid regurgitation

DEFF Research Database (Denmark)

Andersen, Mads Jønsson; Nishimura, Rick a; Borlaug, Barry A

2014-01-01

≥3 TR underwent high-fidelity invasive hemodynamic exercise testing with simultaneous expired gas analysis and were compared with 13 age- and sex-matched controls. At rest, TR subjects had lower pulmonary blood flow (3.6±0.4 versus 5.1±1.9 L/min; P=0.01), increased right atrial pressure (12±5 versus.......001). TR subjects displayed higher pulmonary capillary wedge pressure with exercise, but this was solely because of RA hypertension (27±9 versus 8±3 mm Hg; P......BACKGROUND:Patients with severe tricuspid regurgitation (TR) frequently present with exertional fatigue and dyspnea, but the hemodynamic basis for exercise limitation in people with TR remains unclear. METHODS AND RESULTS:Twelve subjects with normal left ventricular (LV) ejection fraction and grade...

Patient-Specific Modeling of Intraventricular Hemodynamics

Science.gov (United States)

Vedula, Vijay; Marsden, Alison

2017-11-01

Heart disease is the one of the leading causes of death in the world. Apart from malfunctions in electrophysiology and myocardial mechanics, abnormal hemodynamics is a major factor attributed to heart disease across all ages. Computer simulations offer an efficient means to accurately reproduce in vivo flow conditions and also make predictions of post-operative outcomes and disease progression. We present an experimentally validated computational framework for performing patient-specific modeling of intraventricular hemodynamics. Our modeling framework employs the SimVascular open source software to build an anatomic model and employs robust image registration methods to extract ventricular motion from the image data. We then employ a stabilized finite element solver to simulate blood flow in the ventricles, solving the Navier-Stokes equations in arbitrary Lagrangian-Eulerian (ALE) coordinates by prescribing the wall motion extracted during registration. We model the fluid-structure interaction effects of the cardiac valves using an immersed boundary method and discuss the potential application of this methodology in single ventricle physiology and trans-catheter aortic valve replacement (TAVR). This research is supported in part by the Stanford Child Health Research Institute and the Stanford NIH-NCATS-CTSA through Grant UL1 TR001085 and partly through NIH NHLBI R01 Grant 5R01HL129727-02.

Hemodynamic Simulations in Dialysis Access Fistulae

Science.gov (United States)

McGah, Patrick; Leotta, Daniel; Beach, Kirk; Riley, James; Aliseda, Alberto

2010-11-01

Arteriovenous fistulae are created surgically to provide adequate access for dialysis in patients with End-Stage Renal Disease. It has long been hypothesized that the hemodynamic and mechanical forces (such as wall shear stress, wall stretch, or flow- induced wall vibrations) constitute the primary external influence on the remodeling process. Given that nearly 50% of fistulae fail after one year, understanding fistulae hemodynamics is an important step toward improving patency in the clinic. We perform numerical simulations of the flow in patient-specific models of AV fistulae reconstructed from 3D ultrasound scans with physiologically-realistic boundary conditions also obtained from Doppler ultrasound. Comparison of the flow features in different geometries and configurations e.g. end-to-side vs. side-to-side, with the in vivo longitudinal outcomes will allow us to hypothesize which flow conditions are conducive to fistulae success or failure. The flow inertia and pulsatility in the simulations (mean Re 700, max Re 2000, Wo 4) give rise to complex secondary flows and coherent vortices, further complicating the spatio- temporal variability of the wall pressure and shear stresses. Even in mature fistulae, the anastomotic regions are subjected to non-physiological shear stresses (>10.12pcPa) which may potentially lead to complications.

Isolation and Purification of Unstable Iridoid Glucosides from Traditional Chinese Medicine by Preparative High Performance Liquid Chromatography Coupled with Solid-phase Extraction

Institute of Scientific and Technical Information of China (English)

LI Cun-man; XIAO Yuan-sheng; XUE Xing-ya; FENG Jia-tao; ZHANG Xiu-li; LIANG Xin-miao

2011-01-01

An efficient preparative method was successfully developed for isolation and purification of unstable components from medicinal plant extracts, using a combined method of preparative high performance liquid chro matography(HPLC) and solid-phase extraction(SPE). The aim of this study was to obtain an effective method with high preparative efficiency and importantly to avoid the transformation of unstable compounds. The preparative HPLC system was based on an LC/MS controlled four-channel autopurification system. The SPE method was per formed with a C1s packing material to trap the target compounds and to remove the acidic additive derived from the mobile phase. Using this method, the unstable iridoid glucosides(IGs) as model compounds were successfully iso lated and purified from the extract of Hedyotis diffusa Willd. Six IGs(including one new minor IG) and one nucleo tide compound were simultaneously obtained, each with a purity of ＞91% as determined by HPLC. The structures of the isolated compounds were identified by UPLC/Q-TOF MS, UV, ID and/or 2D NMR. It was demonstrated that the combination of preparative HPLC with SPE is a versatile tool for preparative purification of unstable compounds from complex natural products.

Isolation and Purification of Unstable Iridoid Glucosides from Traditional Chinese Medicine by Preparative High Performance Liquid Chromatography Coupled with Solid-phase Extraction

Institute of Scientific and Technical Information of China (English)

无

2011-01-01

An efficient preparative method was successfully developed for isolation and purification of unstable components from medicinal plant extracts, using a combined method of preparative high performance liquid chro-matography（HPLC） and solid-phase extraction（SPE）. The aim of this study was to obtain an effective method with high preparative efficiency and importantly to avoid the transformation of unstable compounds. The preparative HPLC system was based on an LC/MS controlled four-channel autopurification system. The SPE method was performed with a C18 packing material to trap the target compounds and to remove the acidic additive derived from the mobile phase. Using this method, the unstable iridoid glucosides（IGs） as model compounds were successfully isolated and purified from the extract of Hedyotis diffusa Willd. Six IGs（including one new minor IG） and one nucleotide compound were simultaneously obtained, each with a purity of 〉91% as determined by HPLC. The structures of the isolated compounds were identified by UPLC/Q-TOF MS, UV, 1D and/or 2D NMR. It was demonstrated that the combination of preparative HPLC with SPE is a versatile tool for preparative purification of unstable compounds from complex natural products.

Morphological and hemodynamic analysis of mirror posterior communicating artery aneurysms.

Directory of Open Access Journals (Sweden)

Jinyu Xu

Full Text Available BACKGROUND AND PURPOSE: Hemodynamic factors are commonly believed to play an important role in the pathogenesis, progression, and rupture of cerebral aneurysms. In this study, we aimed to identify significant hemodynamic and morphological parameters that discriminate intracranial aneurysm rupture status using 3-dimensional-angiography and computational fluid dynamics technology. MATERIALS AND METHODS: 3D-DSA was performed in 8 patients with mirror posterior communicating artery aneurysms (Pcom-MANs. Each pair was divided into ruptured and unruptured groups. Five morphological and three hemodynamic parameters were evaluated for significance with respect to rupture. RESULTS: The normalized mean wall shear stress (WSS of the aneurysm sac in the ruptured group was significantly lower than that in the unruptured group (0.52±0.20 versus 0.81±0.21, P = .012. The percentage of the low WSS area in the ruptured group was higher than that in the unruptured group (4.11±4.66% versus 0.02±0.06%, P = .018. The AR was 1.04±0.21 in the ruptured group, which was significantly higher than 0.70±0.17 in the unruptured group (P = .012. By contrast, parameters that had no significant differences between the two groups were OSI (P = .674, aneurysm size (P = .327, size ratio (P = .779, vessel angle (P = 1.000 and aneurysm inclination angle (P = 1.000. CONCLUSIONS: Pcom-MANs may be a useful disease model to investigate possible causes of aneurysm rupture. The ruptured aneurysms manifested lower WSS, higher percentage of low WSS area, and higher AR, compared with the unruptured one. And hemodynamics is as important as morphology in discriminating aneurysm rupture status.

The Effect of Inlet Waveforms on Computational Hemodynamics of Patient-Specific Intracranial Aneurysms

OpenAIRE

Xiang, J.; Siddiqui, A.H.; Meng, H.

2014-01-01

Due to the lack of patient-specific inlet flow waveform measurements, most computational fluid dynamics (CFD) simulations of intracranial aneurysms usually employ waveforms that are not patient-specific as inlet boundary conditions for the computational model. The current study examined how this assumption affects the predicted hemodynamics in patient-specific aneurysm geometries. We examined wall shear stress (WSS) and oscillatory shear index (OSI), the two most widely studied hemodynamic qu...

Optical isotope shifts for unstable samarium isotopes

International Nuclear Information System (INIS)

Eastham, D.A.; Walker, P.M.; Griffith, J.A.R.; Evans, D.E.; Grant, I.S.; England, J.G.; Fawcett, M.J.

1984-01-01

Using a tunable dye laser beam intersecting a thermal atomic beam, optical isotope shifts and hyperfine splittings have been measured for the four unstable samarium isotopes between 144 Sm and 154 Sm, covering the well known transition region from spherical to deformed shapes. (orig.)

Numerical simulation of a improving virtual confocal unstable resonator with circular mirrors of spherical surfaces

International Nuclear Information System (INIS)

Wang Taichun; Fu Hanqing; Du Xiangwan

1999-01-01

Based on the analysis of advantages and disadvantages of the unstable resonator with a phase-unifying output coupler, the improving unstable resonator are designed. The numerical simulation results indicate that the improving unstable resonator overcomes disadvantages of that resonator and its far-field intensity focusing is better than the conventional resonator

Lack of evidence for an association between hemodynamic variables and hematoma growth in spontaneous intracerebral hemorrhage.

Science.gov (United States)

Jauch, Edward C; Lindsell, Christopher J; Adeoye, Opeolu; Khoury, Jane; Barsan, William; Broderick, Joseph; Pancioli, Arthur; Brott, Thomas

2006-08-01

Early hematoma expansion in spontaneous intracerebral hemorrhage (ICH) is associated with worse clinical outcome. We hypothesized that hemodynamic parameters are associated with the increase in hematoma volume owing to their relationship to blood vessel wall stresses. We performed a post hoc analysis of clinical and computed tomography (CT) data from patients enrolled in a prospective observational study of ICH patients presenting within 3 hours from symptom onset. Hematoma volumes were measured at hospital arrival and at 1 and 20 hours from presentation. Blood pressure and heart rate, recorded at 19 time points between presentation and 20 hours, were used to derive hemodynamic variables. Multivariable logistic-regression models were constructed to assess the relation between hemodynamic parameters and hematoma growth, adjusted for clinical covariates. From the original study, 98 patients underwent baseline and 1-hour CT scans; of these, 65 had 20-hour CT scans. Substantial hematoma growth was observed in 28% within the first hour. Of the 65 patients not undergoing surgery within 20 hours, 37% experienced hematoma growth by 20 hours. Neither baseline or peak hemodynamic parameters nor changes in hemodynamic parameters were significantly associated with hematoma growth at either 1 or 20 hours. We found no blood pressure or heart rate parameters, individually or in combination, that were associated with hematoma growth. Our data suggest the influence of hemodynamic parameters on vessel wall stress to be an unlikely target for intervention in reducing the risk of early hematoma growth in ICH.

Treatment of unstable trochanteric fractures. Randomised comparison of the gamma nail and the proximal femoral nail.

NARCIS (Netherlands)

Schipper, I.B.; Steyerberg, E.W.; Castelein, R.M.; Heijden, F.H. van der; Hoed, P.T. den; Kerver, A.J.; Vugt, A.B. van

2004-01-01

The proximal femoral nail (PFN) is a recently introduced intramedullary system, designed to improve treatment of unstable trochanteric fractures of the hip. In a multicentre prospective clinical study, the intra-operative use, complications and outcome of treatment using the PFN (n = 211) were

The central hemodynamics at the newborns from the radionuclide contaminated territories

International Nuclear Information System (INIS)

Kalyuzhin, V.G.; Voskresenskaya, T.V.; Deryugina, O.A.; Adas'ko, V.I.; Platonova, O.A.

1995-01-01

As known the cardiovascular system has enough high radiosensitivity. The operation features of the central part of a cardiovascular system of newborns living on contaminated territories were studied. The screening research of a cardiovascular system state of 50 newborns from regions with contamination by 137 Cs more than 15 Ci/sq.km were conducted. The obtained data were compared with results of the similar investigation of 30 newborns from a control 'clean' regions. Is revealed that for newborns from a contaminated zone the more stressed in comparison with one from control group the hemodynamics adaptation process of the central link of a cardiovascular system is characteristic, especially in the first days of a life. For newborns with the disadaptation of a cardiovascular system the constant control for the circulatory homeostasis parameters and more sparing mode of a care in the first days of a life is required. 7 refs., 1 tab

Is the antiproteinuric effect of dipyridamole hemodynamically mediated

NARCIS (Netherlands)

de Jong, P. E.; van der Meer, J.; van der Hem, G. K.; de Zeeuw, D.

1988-01-01

We studied the acute antiproteinuric and renal hemodynamic effect of dipyridamole 30–60 mg intravenously in 13 salt-depleted patients with the nephrotic syndrome of different etiology. Whereas mean arterial pressure did not change, a small fall in glomerular filtration rate with a concomitant fall

Effects of an unstable shoe construction on balance in women aged over 50 years

DEFF Research Database (Denmark)

Ramstrand, Nerrolyn; Thuesen, Anna Helena; Nielsen, Dennis Brandborg

2010-01-01

BACKGROUND: Shoes with an unstable sole construction are commonly used as a therapeutic tool by physiotherapists and are widely available from shoe and sporting goods retailers. The aim of this study was to investigate the effects of using an unstable shoe (Masai Barefoot Technology) on standing ....... INTERPRETATION: Results from the present study suggest that, for this group of individuals, use of unstable footwear may improve certain aspects of balance....

Freedom Solo Versus Trifecta Bioprotheses: Clinical and Hemodynamic Evaluation after Propensity Score Matching.

Science.gov (United States)

J Cerqueira, Rui; Melo, Renata; Moreira, Soraia; A Saraiva, Francisca; Andrade, Marta; Salgueiro, Elson; Almeida, Jorge; J Amorim, Mário; Pinho, Paulo; Lourenço, André; F Leite-Moreira, Adelino

2017-01-01

To compare stentless Freedom Solo and stented Trifecta aortic bioprostheses regarding hemodynamic profile, left ventricular mass regression, early and late postoperative outcomes and survival. Longitudinal cohort study of consecutive patients undergoing aortic valve replacement (from 2009 to 2016) with either Freedom Solo or Trifecta at one centre. Local databases and national records were queried. Postoperative echocardiography (3-6 months) was obtained for hemodynamic profile (mean transprosthetic gradient and effective orifice area) and left ventricle mass determination. After propensity score matching (21 covariates), Kaplan-Meier analysis and cumulative incidence analysis were performed for survival and combined outcome of structural valve deterioration and endocarditis, respectively. Hemodynamics and left ventricle mass regression were assessed by a mixed- -effects model including propensity score as a covariate. From a total sample of 397 Freedom Solo and 525 Trifecta patients with a median follow-up time of 4.0 (2.2- 6.0) and 2.4 (1.4-3.7) years, respectively, a matched sample of 329 pairs was obtained. Well-balanced matched groups showed no difference in survival (hazard ratio=1.04, 95% confidence interval=0.69-1.56) or cumulative hazards of combined outcome (subhazard ratio=0.54, 95% confidence interval=0.21-1.39). Although Trifecta showed improved hemodynamic profile compared to Freedom Solo, no differences were found in left ventricle mass regression. Trifecta has a slightly improved hemodynamic profile compared to Freedom Solo but this does not translate into differences in the extent of mass regression, postoperative outcomes or survival, which were good and comparable for both bioprostheses. Long-term follow-up is needed for comparisons with older models of bioprostheses.

The Effect of Hemodynamics on Cerebral Aneurysm Morphology

Science.gov (United States)

Metcalfe, Ralph; Mantha, Aishwarya; Karmonik, Christof; Strother, Charles

2004-11-01

One of the difficulties in applying principles of hemodynamics to the study of blood flow in aneurysms are the drastic variations in possible shape of both the aneurysms and the parent arteries in the region of interest. We have taken data from three para-opthalmic internal carotid artery aneurysms using 3D-digital subtraction angiography (3D-DSA) and performed CFD simulations of steady and unsteady flows through the three different cases using the same pressure gradients and pulsatile flow waveforms (based on the Ku model for flow through the Carotid bifurcation). We have found that the total pressure differential within the aneurysms is consistent with the direction of flow, and that the dynamic pressure gradient within the aneurysm is very small compared with the static pressure variations. Wall shear stresses were highest near regions of sharp arterial curvature, but always remained low inside the aneurysm. These results suggest a more complex role for hemodynamics in aneurysm generation, growth and rupture.

Robotic tilt table reduces the occurrence of orthostatic hypotension over time in vegetative states.

Science.gov (United States)

Taveggia, Giovanni; Ragusa, Ivana; Trani, Vincenzo; Cuva, Daniele; Angeretti, Cristina; Fontanella, Marco; Panciani, Pier Paolo; Borboni, Alberto

2015-06-01

The aim of this study is to evaluate the effects of verticalization with or without combined movement of the lower limbs in patients in a vegetative state or a minimally conscious state. In particular, we aimed to study whether, in the group with combined movement, there was better tolerance to verticalization. This was a randomized trial conducted in a neurorehabilitation hospital. Twelve patients with vegetative state and minimally conscious state 3-18 months after acute acquired brain injuries were included. Patients were randomized into A and B treatment groups. Study group A underwent verticalization with a tilt table at 65° and movimentation of the lower limbs with a robotic system for 30 min three times a week for 24 sessions. Control group B underwent the same rehabilitation treatment, with a robotic verticalization system, but an inactive lower-limb movement system. Systolic and diastolic blood pressure and heart rate were determined. Robotic movement of the lower limbs can reduce the occurrence of orthostatic hypotension in hemodynamically unstable patients. Despite the small number of patients involved (only eight patients completed the trial), our results indicate that blood pressures and heart rate can be stabilized better (with) by treatment with passive leg movements in hemodynamically unstable patients.

Place of Arterial Embolization in Severe Blunt Hepatic Trauma: A Multidisciplinary Approach

International Nuclear Information System (INIS)

Monnin, Valerie; Sengel, Christian; Thony, Frederic; Bricault, Ivan; Voirin, David; Letoublon, Christian; Broux, Christophe; Ferretti, Gilbert

2008-01-01

This study evaluates the efficacy of arterial embolization (AE) for blunt hepatic traumas (BHT) as part of a combined management strategy based on the hemodynamic status of patients and CT findings. From 2000 to 2005, 84 patients were admitted to our hospital for BHT. Of these, 14 patients who had high-grade injuries (grade III [n = 2], grade IV [n = 9], grade V [n = 3]) underwent AE because of arterial bleeding and were included in the study. They were classified into three groups according to their hemodynamic status: (1) unresponsive shock, (2) shock improved with resuscitation, and (3) hemodynamic stability. Four patients (group 1) underwent, first, laparotomy with packing and, then, AE for persistent bleeding. Ten patients who were hemodynamically stable (group 1) or even unstable (group 2) underwent AE first, based on CT findings. AE was successful in all cases. The mortality rate was 7% (1/14). Only two angiography-related complications (gallbladder infarction) were reported. Liver-related complications (abdominal compartment syndrome and biliary complications) were frequent and often required secondary interventions. Our multidisciplinary approach for the management of BHT gives a main role to embolization, even for hemodynamically unstable patients. In this strategy AE is very efficient and has a low complication rate.

Unifying treatment of nonequilibrium and unstable dynamics of cold bosonic atom system with time-dependent order parameter in Thermo Field Dynamics

International Nuclear Information System (INIS)

Nakamura, Y.; Yamanaka, Y.

2011-01-01

Research highlights: → Cold atoms with time-dependent condensate in nonequilibrium Thermo Field Dynamics. → Coupled equations which describe the temporal evolution of the system are derived. → They are not the naive assemblages of presumable equations, but the self-consistently ones. → Valid even for systems with Landau or dynamical instability, and describing decays. → Transport equation has new collision term that is important in Landau instability. - Abstract: The coupled equations which describe the temporal evolution of the Bose-Einstein condensed system are derived in the framework of nonequilibrium Thermo Field Dynamics. The key element is that they are not the naive assemblages of assumed equations, but are the self-consistent ones derived by appropriate renormalization conditions. While the order parameter is time-dependent, an explicit quasiparticle picture is constructed by a time-dependent expansion. Our formulation is valid even for the system with a unstable condensate, and describes the condensate decay caused by the Landau instability as well as by the dynamical one.

Ultrasound investigation central hemodynamics as a method of assessment effective analgesia in children

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K. Y. Dmytriieva

2016-06-01

Vinnitsa National Medical University M.I. Pirogov   Summary: The study was include in 23 children (12,4±1,2 years operated on for tumors of the retroperitoneal space (14 children, 61%, renal tumors (6 children, 26%, ovarian cancer (3 children, 13% showed that a comprehensive study of the reactions of pain behavior and central hemodynamics by ultrasonography showed that the use of the scheme KSME bupivacaine 0.3-0.4 mg / kg and a continuous infusion of drugs (fentanyl in a dose of 10 mcg/kg/h for postoperative pain relief leads to effective analgesia after traumatic operations and comprehensive ultrasound including color and spectral Doppler studies, is the main tool by enabling timely and accurately assess the condition of the central hemodynamics at different methods of analgesia.   Key words: central hemodynamics, ultrasound, anesthesia.

[Effect of complex sanatorium treatment including magnetotherapy on hemodynamics in patients with arterial hypertension].

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Efremushkin, G G; Duruda, N V

2003-01-01

Forty nine patients with arterial hypertension of stage I-II received combined sanatorium treatment. Of them, 21 had adjuvant total magnetotherapy. All the patients were examined for parameters of central, cerebral hemodynamics and microcirculation. The adjuvant magnetotherapy produced a beneficial effect on hypertension: clinical symptoms attenuated, arterial pressure became more stable, hemodynamics improved, duration of hospitalization reduced, requirement in hypotensive drugs diminished.

Impact of Clipping versus Coiling on Postoperative Hemodynamics and Pulmonary Edema after Subarachnoid Hemorrhage

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Nobutaka Horie

2014-01-01

Full Text Available Volume management is critical for assessment of cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH. This multicenter prospective cohort study compared the impact of surgical clipping versus endovascular coiling on postoperative hemodynamics and pulmonary edema in patients with SAH. Hemodynamic parameters were measured for 14 days using a transpulmonary thermodilution system. The study included 202 patients, including 160 who underwent clipping and 42 who underwent coiling. There were no differences in global ejection fraction (GEF, cardiac index, systemic vascular resistance index, or global end-diastolic volume index between the clipping and coiling groups in the early period. However, extravascular lung water index (EVLWI and pulmonary vascular permeability index (PVPI were significantly higher in the clipping group in the vasospasm period. Postoperative C-reactive protein (CRP level was higher in the clipping group and was significantly correlated with postoperative brain natriuretic peptide level. Multivariate analysis found that PVPI and GEF were independently associated with high EVLWI in the early period, suggesting cardiogenic edema, and that CRP and PVPI, but not GEF, were independently associated with high EVLWI in the vasospasm period, suggesting noncardiogenic edema. In conclusion, clipping affects postoperative CRP level and may thereby increase noncardiogenic pulmonary edema in the vasospasm period. His trial is registered with University Hospital Medical Information Network UMIN000003794.

Implications of the Hemodynamic Optimization Approach Guided by Right Heart Catheterization in Patients with Severe Heart Failure

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Luís E. Rohde

2002-03-01

Full Text Available OBJECTIVE: To report the hemodynamic and functional responses obtained with clinical optimization guided by hemodynamic parameters in patients with severe and refractory heart failure. METHODS: Invasive hemodynamic monitoring using right heart catheterization aimed to reach low filling pressures and peripheral resistance. Frequent adjustments of intravenous diuretics and vasodilators were performed according to the hemodynamic measurements. RESULTS: We assessed 19 patients (age = 48±12 years and ejection fraction = 21±5% with severe heart failure. The intravenous use of diuretics and vasodilators reduced by 12 mm Hg (relative reduction of 43% pulmonary artery occlusion pressure (P<0.001, with a concomitant increment of 6 mL per beat in stroke volume (relative increment of 24%, P<0.001. We observed significant associations between pulmonary artery occlusion pressure and mean pulmonary artery pressure (r=0.76; P<0.001 and central venous pressure (r=0.63; P<0.001. After clinical optimization, improvement in functional class occurred (P< 0.001, with a tendency towards improvement in ejection fraction and no impairment to renal function. CONCLUSION: Optimization guided by hemodynamic parameters in patients with refractory heart failure provides a significant improvement in the hemodynamic profile with concomitant improvement in functional class. This study emphasizes that adjustments in blood volume result in imme-diate benefits for patients with severe heart failure.

Trunk muscle activity increases with unstable squat movements.

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Anderson, Kenneth; Behm, David G

2005-02-01

The objective of this study was to determine differences in electromyographic (EMG) activity of the soleus (SOL), vastus lateralis (VL), biceps femoris (BF), abdominal stabilizers (AS), upper lumbar erector spinae (ULES), and lumbo-sacral erector spinae (LSES) muscles while performing squats of varied stability and resistance. Stability was altered by doing the squat movement on a Smith machine, a free squat, and while standing on two balance discs. Fourteen male subjects performed the movements. Activities of the SOL, AS, ULES, and LSES were highest during the unstable squat and lowest with the Smith machine protocol (p squats on unstable surfaces may permit a training adaptation of the trunk muscles responsible for supporting the spinal column (i.e., erector spinae) as well as the muscles most responsible for maintaining posture (i.e., SOL).

Gamma-unstable nuclei in the sdg boson model

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Kuyucak, S.; Lac, V.-S.; Morrison, I.; Barret, B. R.

Following the recent Pt(p,p') experiments which indicated the need for high angular momentum (g) bosons to reproduce the E4 data, we have extended the O(6) limit of the sd boson model to the sdg bosons. It is shown that a gamma-unstable Hamiltonian in the sdg model consisting of a quadrupole interaction and a g boson energy leads to results that are very similar to the O(6) limit. Deviations from the empirical energy spectrum that stem from the gamma-unstable nature of the Hamiltonian can be improved by including a consistent hexadecapole interaction which induces triaxiality. The same hexadecapole operator can also account for the strong E4 transitions to the 4(sup +) states presumed to be g boson states. Specific applications are made to the Xe and Pt isotopes.

Multiparametric estimation of brain hemodynamics with MR fingerprinting ASL.

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Su, Pan; Mao, Deng; Liu, Peiying; Li, Yang; Pinho, Marco C; Welch, Babu G; Lu, Hanzhang

2017-11-01

Assessment of brain hemodynamics without exogenous contrast agents is of increasing importance in clinical applications. This study aims to develop an MR perfusion technique that can provide noncontrast and multiparametric estimation of hemodynamic markers. We devised an arterial spin labeling (ASL) method based on the principle of MR fingerprinting (MRF), referred to as MRF-ASL. By taking advantage of the rich information contained in MRF sequence, up to seven hemodynamic parameters can be estimated concomitantly. Feasibility demonstration, flip angle optimization, comparison with Look-Locker ASL, reproducibility test, sensitivity to hypercapnia challenge, and initial clinical application in an intracranial steno-occlusive process, Moyamoya disease, were performed to evaluate this technique. Magnetic resonance fingerprinting ASL provided estimation of up to seven parameters, including B1+, tissue T 1 , cerebral blood flow (CBF), tissue bolus arrival time (BAT), pass-through arterial BAT, pass-through blood volume, and pass-through blood travel time. Coefficients of variation of the estimated parameters ranged from 0.2 to 9.6%. Hypercapnia resulted in an increase in CBF by 57.7%, and a decrease in BAT by 13.7 and 24.8% in tissue and vessels, respectively. Patients with Moyamoya disease showed diminished CBF and lengthened BAT that could not be detected with regular ASL. Magnetic resonance fingerprinting ASL is a promising technique for noncontrast, multiparametric perfusion assessment. Magn Reson Med 78:1812-1823, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Wind tunnel experiments on unstable self-excited vibration of sectional girders

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Král, Radomil; Pospíšil, Stanislav; Náprstek, Jiří

2014-01-01

In this paper, a wind tunnel analysis of two degrees-of-freedom system represented by sectional girders is carried out. Besides an evaluation of the aeroelastic coefficients, the analysis is focused on the influence of the natural frequency ratio on the initiation of unstable vibration, which can be of practical interest. On the phenomenological level, the paper also discusses experimentally ascertained response regimes, with an emphasis on their stability character. The attention is paid to the memory effect in the response described by the hysteresis loop together with the separation curves determining the stability boundaries. The influence of initial disturbance on the stability is examined. Two types of cross-sections were investigated: (i) rectangular one with the aspect ratio 1:5, and (ii) bridge-like cross-section with comparable principal dimensions. For both types of cross-sections, the limits of the stability are significantly affected by an intentionally introduced initial disturbance. This holds especially with regard to the rectangular profile where the separation curves create very narrow sub-domains between a stable and an unstable response, while the bridge-like cross-section demonstrates much stable behaviour.

Cerebrovascular Hemodynamics in Women.

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Duque, Cristina; Feske, Steven K; Sorond, Farzaneh A

2017-12-01

Sex and gender, as biological and social factors, significantly influence health outcomes. Among the biological factors, sex differences in vascular physiology may be one specific mechanism contributing to the observed differences in clinical presentation, response to treatment, and clinical outcomes in several vascular disorders. This review focuses on the cerebrovascular bed and summarizes the existing literature on sex differences in cerebrovascular hemodynamics to highlight the knowledge deficit that exists in this domain. The available evidence is used to generate mechanistically plausible and testable hypotheses to underscore the unmet need in understanding sex-specific mechanisms as targets for more effective therapeutic and preventive strategies. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Clinical Implications of Cluster Analysis-Based Classification of Acute Decompensated Heart Failure and Correlation with Bedside Hemodynamic Profiles.

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Tariq Ahmad

Full Text Available Classification of acute decompensated heart failure (ADHF is based on subjective criteria that crudely capture disease heterogeneity. Improved phenotyping of the syndrome may help improve therapeutic strategies.To derive cluster analysis-based groupings for patients hospitalized with ADHF, and compare their prognostic performance to hemodynamic classifications derived at the bedside.We performed a cluster analysis on baseline clinical variables and PAC measurements of 172 ADHF patients from the ESCAPE trial. Employing regression techniques, we examined associations between clusters and clinically determined hemodynamic profiles (warm/cold/wet/dry. We assessed association with clinical outcomes using Cox proportional hazards models. Likelihood ratio tests were used to compare the prognostic value of cluster data to that of hemodynamic data.We identified four advanced HF clusters: 1 male Caucasians with ischemic cardiomyopathy, multiple comorbidities, lowest B-type natriuretic peptide (BNP levels; 2 females with non-ischemic cardiomyopathy, few comorbidities, most favorable hemodynamics; 3 young African American males with non-ischemic cardiomyopathy, most adverse hemodynamics, advanced disease; and 4 older Caucasians with ischemic cardiomyopathy, concomitant renal insufficiency, highest BNP levels. There was no association between clusters and bedside-derived hemodynamic profiles (p = 0.70. For all adverse clinical outcomes, Cluster 4 had the highest risk, and Cluster 2, the lowest. Compared to Cluster 4, Clusters 1-3 had 45-70% lower risk of all-cause mortality. Clusters were significantly associated with clinical outcomes, whereas hemodynamic profiles were not.By clustering patients with similar objective variables, we identified four clinically relevant phenotypes of ADHF patients, with no discernable relationship to hemodynamic profiles, but distinct associations with adverse outcomes. Our analysis suggests that ADHF classification using

Hemodynamic evaluation of the right portal vein in healthy dogs of different body weights

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de Almeida Mariana F

2010-05-01

Full Text Available Abstract Background Doppler ultrasonography is an important tool for evaluating hepatic portal hemodynamics. However, no study in dogs of different body weights, in the range encountered in routine clinical veterinary practice, has been reported. It can be difficult to obtain an ideal insonation angle when evaluating the main portal vein, so evaluation of the right portal vein branch has been described in humans as an alternative. The aim of this study was to analyze, through Doppler ultrasonography, the hemodynamics in the right portal vein branch in dogs of different body weights. Methods Thirty normal dogs were divided in three groups by weight, in order to establish normal values for mean velocity, flow volume and portal congestion index of the right portal vein branch by means of Doppler ultrasonography. Results In all dogs ideal insonation angles were obtained for the right portal vein branch. The average velocity was similar in the three groups, but the portal congestion index and the flow volume differed, showing that the weight of the dog can influence these values. Conclusion Doppler ultrasonography for the evaluation of flow in the right branch of the portal vein could be a viable alternative, or complement, to examining the main vessel segment. This is especially so in those animals in which an ideal insonation angle for examination of the main portal vein is hard to obtain. In addition, the weight of the dog must be considered for the correct evaluation of the portal system hemodynamics, particularly for portal blood flow and the congestion index.

Novel method to classify hemodynamic response obtained using multi-channel fNIRS measurements into two groups: Exploring the combinations of channels

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Hiroko eIchikawa

2014-07-01

Full Text Available Near-infrared spectroscopy (NIRS in psychiatric studies has widely demonstrated that cerebral hemodynamics differs among psychiatric patients. Recently we found that children with attention attention-deficit / hyperactivity disorder (ADHD and children with autism spectrum disorders (ASD showed different hemodynamic responses to their own mother’s face. Based on this finding, we may be able to classify their hemodynamic data into two those groups and predict which diagnostic group an unknown participant belongs to. In the present study, we proposed a novel statistical method for classifying the hemodynamic data of these two groups. By applying a support vector machine (SVM, we searched the combination of measurement channels at which the hemodynamic response differed between the two groups; ADHD and ASD. The SVM found the optimal subset of channels in each data set and successfully classified the ADHD data from the ASD data. For the 24-dimentional hemodynamic data, two optimal subsets classified the hemodynamic data with 84% classification accuracy while the subset contains all 24 channels classified with 62% classification accuracy. These results indicate the potential application of our novel method for classifying the hemodynamic data into two groups and revealing the combinations of channels that efficiently differentiate the two groups.

A pilot study on the influence of exercising on unstable training machine on balance control and trunk muscles activity.

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Domeika, Aurelijus; Aleknaite-Dambrauskiene, Ieva; Poskaitis, Vytautas; Zaveckas, Vidmantas; Grigas, Vytautas; Zvironiene, Ausra

2018-05-16

The main position of the working population is becoming sitting. Immobile prolonged sedentary time may cause negative effects including reduced intervertebral discs nutrition. Main ways of mitigating them are regular position changes and exercising. To evaluate influence of the short term training on unstable training machine on balance control and trunk muscles activity in patients with lower back pain. Participants (n=16) experiencing lower back pain were trained on an unstable sculling machine "Rehabili". Their balance tested by (Biodex Balance System) and rectus abdominis, externus oblique, transverse abdominis, multifidus and erector spine muscles activity (measured by surface electromyography) while sitting and standing with usual and aligned body postures both before and after six weeks of training (three 15 minutes sessions per week) were compared in between. Balance control improved after the training program. Besides, more symmetrical activation of both sides rectus and transversus abdominis muscles, as well as increased transversus abdominis muscle activation of 19% (p< 0.05), were observed. Six weeks short sessions training on unstable training machine improved balance control and increased trunk muscles activity especially in aligned body posture when standing or sitting on unstable surface.

The azimuthally anisotropic emission of unstable light nuclear in the heavy ion collisions at intermediate energy

International Nuclear Information System (INIS)

He Zhiyong; Jin Genming; Li Zuyu; Duan Limin; Dai Guangxi; Zhang Baoguo; Wu Heyu; Wen Wanxin; Qi Yujin; Luo Qingzheng

1996-01-01

The unstable light nuclei emitted in the interaction of 40 Ar on 197 Au have been detected at energy of 25 MeV/u by using particle-particle correlation measurement at small relative angle. Their in-plane and out-of-plane emission were measured for three bins of experimentally estimated impact parameter. The enhanced in-plane emission for mid-rapidity unstable nuclei is observed. This enhanced in-plane emission becomes stronger with increasing of impact parameter, but changes small with the mass of unstable nuclei. The in-plane enhancement decreases slightly with the energy of excited state of unstable nuclei. For projectile-like unstable nuclei, the in-plane emission dominates as expected

Hemodynamic challenge to early mobilization after cardiac surgery: A pilot study

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Tiziano Cassina

2016-01-01

Full Text Available Background: Active mobilization is a key component in fast-track surgical strategies. Following major surgery, clinicians are often reluctant to mobilize patients arguing that circulatory homeostasis would be impaired as a result of myocardial stunning, fluid shift, and autonomic dysfunction. Aims: We examined the feasibility and safety of a mobilization protocol 12-24 h after elective cardiac surgery. Setting and Design: This observational study was performed in a tertiary nonacademic cardiovascular Intensive Care Unit. Materials and Methods: Over a 6-month period, we prospectively evaluated the hemodynamic response to a two-staged mobilization procedure in 53 consecutive patients. Before, during, and after the mobilization, hemodynamics parameters were recorded, including the central venous oxygen saturation (ScvO 2 , lactate concentrations, mean arterial pressure (MAP, heart rate (HR, right atrial pressure (RAP, and arterial oxygen saturation (SpO 2 . Any adverse events were documented. Results: All patients successfully completed the mobilization procedure. Compared with the supine position, mobilization induced significant increases in arterial lactate (34.6% [31.6%, 47.6%], P = 0.0022 along with reduction in RAP (−33% [−21%, −45%], P 10% and nine of them (17% required treatment. Hypotensive patients experienced a greater decrease in ScvO 2 (−18 ± 5% vs. −9 ± 4%, P = 0.004 with similar changes in RAP and HR. All hemodynamic parameters, but arterial lactate, recovered baseline values after resuming the horizontal position. Conclusions: Early mobilization after cardiac surgery appears to be a safe procedure as far as it is performed under close hemodynamic and clinical monitoring in an intensive care setting.

Clofibrate prevents and reverses the hemodynamic manifestations of hyperthyroidism in rats.

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Rodríguez-Gómez, Isabel; Cruz, Antonio; Moreno, Juan Manuel; Soler, Agatángelo; Osuna, Antonio; Vargas, Félix

2008-03-01

This study analyzed the effects of the chronic administration of clofibrate, a peroxisome proliferator-activated receptor-alpha (PPARalpha) agonist, on the development and established hemodynamic, morphologic, metabolic, and renal manifestations of hyperthyroidism in rats. The prevention study used four groups of male Wistar rats: control, clofibrate (240 mg/kg/day by gavage), T(4)(75 microg thyroxine/rat/day s.c.), and T(4)+clofibrate. All treatments were maintained for 3 weeks. Body weight (BW), tail systolic blood pressure (SBP), and heart rate (HR) were recorded weekly. Finally, temperature, SBP, pulse pressure (PP) and HR were recorded in conscious rats, and morphologic, metabolic, plasma, and renal variables were measured. The reversion study used two groups of rats, T(4)(treated for 6 weeks) and T(4)+clofibrate, measuring their hemodynamic variables and temperature for 3 weeks. T(4) increased BP, HR, PP, and temperature when compared with control rats. Clofibrate prevented and reversed the increase in SBP, HR, PP, and temperature produced by T(4) administration, reduced plasma thyroid hormone levels, and increased plasma thyroid-stimulating hormone values and phenol-uridine diphosphate-glucuronosyl-transferase (UGT) activity. However, clofibrate did not modify the cardiac or renal hypertrophy, polyphagia, polydipsia, or proteinuria of hyperthyroid rats. In normal rats, clofibrate treatment did not significantly change thyroid hormone levels, phenol-UGT activity, or any hemodynamic, morphologic, or renal variables. Chronic clofibrate treatment suppressed the hemodynamic manifestations and increased temperature of hyperthyroidism, an effect that can be produced by direct antithyroid effects. However, clofibrate administration did not modify the morphologic, metabolic, or renal alterations of hyperthyroid rats, indicating specificity in the antithyroid actions of clofibrate.

Dynamics of unstable systems

International Nuclear Information System (INIS)

Posch, H.A.; Narnhofer, H.; Thirring, W.

1990-01-01

We study the dynamics of classical particles interacting with attractive Gaussian potentials. This system is thermodynamically not stable and exhibits negative specific heat. The results of the computer simulation of the dynamics are discussed in comparison with various theories. In particular, we find that the condensed phase is a stationary solution of the Vlasov equation, but the Vlasov dynamics cannot describe the collapse. 14 refs., 1 tab., 11 figs. (Authors)

Endovascular management of renal transplant dysfunction secondary to hemodynamic effects related to ipsilateral femoral arteriovenous graft

Science.gov (United States)

Salsamendi, Jason; Pereira, Keith; Quintana, David; Bleicher, Drew; Tabbara, Marwan; Goldstein, Michael; Narayanan, Govindarajan

2016-01-01

Hemodialysis access options become complex in long-term treatment for patients with renal disease, while awaiting renal transplantation (RT). Once upper extremity sites are exhausted, lower extremities are used. RT is preferably in the contralateral iliac fossa, rarely ipsilateral. In current literature, RT dysfunction secondary to the hemodynamic effects of an ipsilateral femoral arteriovenous graft (AVG) has been rarely described. To our knowledge, AVG ligation is the only published technique for hemodynamic correction of an ipsilateral AVG. We present a simple, potentially reversible endovascular approach to manage the hemodynamic effects of an AVG, without potentially permanently losing future AVG access. PMID:26899147

Biomechanical and Hemodynamic Measures of Right Ventricular Diastolic Function: Translating Tissue Biomechanics to Clinical Relevance.

Science.gov (United States)

Jang, Sae; Vanderpool, Rebecca R; Avazmohammadi, Reza; Lapshin, Eugene; Bachman, Timothy N; Sacks, Michael; Simon, Marc A

2017-09-12

Right ventricular (RV) diastolic function has been associated with outcomes for patients with pulmonary hypertension; however, the relationship between biomechanics and hemodynamics in the right ventricle has not been studied. Rat models of RV pressure overload were obtained via pulmonary artery banding (PAB; control, n=7; PAB, n=5). At 3 weeks after banding, RV hemodynamics were measured using a conductance catheter. Biaxial mechanical properties of the RV free wall myocardium were obtained to extrapolate longitudinal and circumferential elastic modulus in low and high strain regions (E 1 and E 2 , respectively). Hemodynamic analysis revealed significantly increased end-diastolic elastance (E ed ) in PAB (control: 55.1 mm Hg/mL [interquartile range: 44.7-85.4 mm Hg/mL]; PAB: 146.6 mm Hg/mL [interquartile range: 105.8-155.0 mm Hg/mL]; P =0.010). Longitudinal E 1 was increased in PAB (control: 7.2 kPa [interquartile range: 6.7-18.1 kPa]; PAB: 34.2 kPa [interquartile range: 18.1-44.6 kPa]; P =0.018), whereas there were no significant changes in longitudinal E 2 or circumferential E 1 and E 2 . Last, wall stress was calculated from hemodynamic data by modeling the right ventricle as a sphere: stress=Pressure×radius2×thickness. RV pressure overload in PAB rats resulted in an increase in diastolic myocardial stiffness reflected both hemodynamically, by an increase in E ed , and biomechanically, by an increase in longitudinal E 1 . Modest increases in tissue biomechanical stiffness are associated with large increases in E ed . Hemodynamic measurements of RV diastolic function can be used to predict biomechanical changes in the myocardium. © 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.

Encephalic hemodynamic phases in subarachnoid hemorrhage: how to improve the protective effect in patient prognoses

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Marcelo de Lima Oliveira

2015-01-01

Full Text Available Subarachnoid hemorrhage is frequently associated with poor prognoses. Three different hemodynamic phases were identified during subarachnoid hemorrhage: oligemia, hyperemia, and vasospasm. Each phase is associated with brain metabolic changes. In this review, we correlated the hemodynamic phases with brain metabolism and potential treatment options in the hopes of improving patient prognoses.

Weak correlations between hemodynamic signals and ongoing neural activity during the resting state

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Winder, Aaron T.; Echagarruga, Christina; Zhang, Qingguang; Drew, Patrick J.

2017-01-01

Spontaneous fluctuations in hemodynamic signals in the absence of a task or overt stimulation are used to infer neural activity. We tested this coupling by simultaneously measuring neural activity and changes in cerebral blood volume (CBV) in the somatosensory cortex of awake, head-fixed mice during periods of true rest, and during whisker stimulation and volitional whisking. Here we show that neurovascular coupling was similar across states, and large spontaneous CBV changes in the absence of sensory input were driven by volitional whisker and body movements. Hemodynamic signals during periods of rest were weakly correlated with neural activity. Spontaneous fluctuations in CBV and vessel diameter persisted when local neural spiking and glutamatergic input was blocked, and during blockade of noradrenergic receptors, suggesting a non-neuronal origin for spontaneous CBV fluctuations. Spontaneous hemodynamic signals reflect a combination of behavior, local neural activity, and putatively non-neural processes. PMID:29184204

Gender-specific hemodynamics in prefrontal cortex during a verbal working memory task by near-infrared spectroscopy.

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Li, Ting; Luo, Qingming; Gong, Hui

2010-05-01

The presence or absence of gender differences in working memory, localized in the prefrontal cortex (PFC), has been debated in a few fMRI studies. However, the hypothesis of gender differences in PFC function has not been elaborated, and comparisons among hemodynamic parameters designed to test for gender differences are scarce. We utilized near-infrared spectroscopy during verbal N-back tasks on 26 male and 24 female healthy volunteers. Changes in the concentrations of oxy- (Delta[oxy-Hb]), deoxy- (Delta[deoxy-Hb]) and total hemoglobin (Delta[tot-Hb]) were recorded simultaneously. Delta[oxy-Hb] and Delta[tot-Hb] exhibited obvious gender differences, but Delta[deoxy-Hb] did not. Males showed bilateral activation with slight left-side dominance, whereas females showed left activation. The activation in males was more wide-spread and stronger than in females. Furthermore, females required a lower hemodynamic supply than males to obtain comparable performance, and only females exhibited positive correlations between hemodynamic parameters and behavioral performance. The results reinforce the existence of a gender effect in hemodynamic-based functional imaging studies. Our findings suggest that females possess more efficient hemodynamics in the PFC during working memory and emphasize the importance of studying the PFC to further a scientific understanding of gender differences.

An efficient identification approach for stable and unstable nonlinear systems using Colliding Bodies Optimization algorithm.

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Pal, Partha S; Kar, R; Mandal, D; Ghoshal, S P

2015-11-01

This paper presents an efficient approach to identify different stable and practically useful Hammerstein models as well as unstable nonlinear process along with its stable closed loop counterpart with the help of an evolutionary algorithm as Colliding Bodies Optimization (CBO) optimization algorithm. The performance measures of the CBO based optimization approach such as precision, accuracy are justified with the minimum output mean square value (MSE) which signifies that the amount of bias and variance in the output domain are also the least. It is also observed that the optimization of output MSE in the presence of outliers has resulted in a very close estimation of the output parameters consistently, which also justifies the effective general applicability of the CBO algorithm towards the system identification problem and also establishes the practical usefulness of the applied approach. Optimum values of the MSEs, computational times and statistical information of the MSEs are all found to be the superior as compared with those of the other existing similar types of stochastic algorithms based approaches reported in different recent literature, which establish the robustness and efficiency of the applied CBO based identification scheme. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Pipeline modeling and assessment in unstable slopes

Energy Technology Data Exchange (ETDEWEB)

Caceres, Carlos Nieves [Oleoducto Central S.A., Bogota, Cundinamarca (Colombia); Ordonez, Mauricio Pereira [SOLSIN S.A.S, Bogota, Cundinamarca (Colombia)

2010-07-01

The OCENSA pipeline system is vulnerable to geotechnical problems such as faults, landslides or creeping slopes, which are well-known in the Andes Mountains and tropical countries like Colombia. This paper proposes a methodology to evaluate the pipe behaviour during the soil displacements of slow landslides. Three different cases of analysis are examined, according to site characteristics. The process starts with a simplified analytical model and develops into 3D finite element numerical simulations applied to the on-site geometry of soil and pipe. Case 1 should be used when the unstable site is subject to landslides impacting significant lengths of pipeline, pipeline is straight, and landslide is simple from the geotechnical perspective. Case 2 should be used when pipeline is straight and landslide is complex (creeping slopes and non-conventional stabilization solutions). Case 3 should be used if the pipeline presents vertical or horizontal bends.

Modeling of supermodes in coupled unstable resonators

International Nuclear Information System (INIS)

Townsend, S.S.

1986-01-01

A general formalism describing the supermodes of an array of N identical, circulantly coupled resonators is presented. The symmetry of the problem results in a reduction of the N coupled integral equations to N decoupled integral equations. Each independent integral equation defines a set of single-resonator modes derived for a hypothetical resonator whose geometry resembles a member of the real array with the exception that all coupling beams are replaced by feedback beams, each with a prescribed constant phase. A given array supermode consists of a single equivalent resonator mode appearing repetitively in each resonator with a prescribed relative phase between individual resonators. The specific array design chosen for example is that of N adjoint coupled confocal unstable resonators. The impact of coupling on the computer modeling of this system is discussed and computer results for the cases of two- and four-laser coupling are presented

Review: hemodynamic response to carbon monoxide

Energy Technology Data Exchange (ETDEWEB)

Penney, D.G.

1988-04-01

Historically, and at present, carbon monoxide is a major gaseous poison responsible for widespread morbidity and mortality. From threshold to maximal nonlethal levels, a variety of cardiovascular changes occur, both immediately and in the long term, whose homeostatic function it is to renormalize tissue oxygen delivery. However, notwithstanding numerous studies over the past century, the literature remains equivocal regarding the hemodynamic responses in animals and humans, although CO hypoxia is clearly different in several respects from hypoxic hypoxia. Factors complicating interpretation of experimental findings include species, CO dose level and rate, route of CO delivery, duration, level of exertion, state of consciousness, and anesthetic agent used. Augmented cardiac output usually observed with moderate COHb may be compromised in more sever poisoning for the same reasons, such that regional or global ischemia result. The hypotension usually seen in most animal studies is thought to be a primary cause of CNS damage resulting from acute CO poisoning, yet the exact mechanism(s) remains unproven in both animals and humans, as does the way in which CO produces hypotension. This review briefly summarizes the literature relevant to the short- and long-term hemodynamic responses reported in animals and humans. It concludes by presenting an overview using data from a single species in which the most complete work has been done to date.

Augmentation of sensory-evoked hemodynamic response in an early Alzheimer's disease mouse model.

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Kim, Jinho; Jeong, Yong

2013-01-01

Based on enlarged blood oxygen level-dependent (BOLD) responses in cognitively normal subjects at risk for Alzheimer's disease (AD), compensatory neuronal hyperactivation has been proposed as an early marker for diagnosis of AD. The BOLD response results from neurovascular coupling, i.e., hemodynamic response induced by neuronal activity. However, there has been no evidence of task-induced increases in hemodynamic response in animal models of AD. Here, we observed an augmented hemodynamic response pattern in a transgenic AβPP(SWE)/PS1ΔE9 mouse model of AD using three in vivo imaging methods: intrinsic optical signal imaging, multi-photon laser scanning microscopy, and laser Doppler flowmetry. Sensory stimulation resulted in augmented and prolonged hemodynamic responses in transgenic mice evidenced by changes in total, oxygenated, and deoxygenated hemoglobin concentration. This difference between transgenic and wild-type mice was significant at 7 months of age when amyloid plaques and cerebral amyloid angiopathy had developed but not at younger or older ages. Correspondingly, sensory stimulation-induced pial arteriole diameter was also augmented and prolonged in transgenic mice at 7 months of age. Cerebral blood flow response in transgenic mice was augmented but not prolonged. These results are consistent with the existence of BOLD signal hyperactivation in non-demented AD-risk human subjects, supporting its potential use as an early diagnostic marker of AD.

Theory of elementary excitations in unstable Bose-Einstein condensates and the instability of sonic horizons

International Nuclear Information System (INIS)

Leonhardt, U.; Kiss, T.; Oehberg, P.

2003-01-01

Like classical fluids, quantum gases may suffer from hydrodynamic instabilities. Our paper develops a quantum version of the classical stability analysis in fluids, the Bogoliubov theory of elementary excitations in unstable Bose-Einstein condensates. In unstable condensates the excitation modes have complex frequencies. We derive the normalization conditions for unstable modes such that they can serve in a mode decomposition of the noncondensed component. Furthermore, we develop approximative techniques to determine the spectrum and the mode functions. Finally, we apply our theory to sonic horizons - sonic black and white holes. For sonic white holes the spectrum of unstable modes turns out to be intrinsically discrete, whereas black holes may be stable

Search for unstable photinos

International Nuclear Information System (INIS)

Mayer, P.

1987-04-01

We have searched in e + e - -annihilation for the photino, the partner of the photon, which is predicted by supersymmetry. Photinos can be pair produced in e + e - annihilation by the exchange of a scalar electron, the partner of the electron. It was assumed that the photino is unstable and decays in a photon and a lighter supersymmetric particle. This second particle leaves the detector unobserved. In the final state one sees then two photons with missing energy and missing momentum. The data were taken with the detector CELLO at the e + e - storage ring PETRA at DESY, Hamburg. The CMS energy was between 38.3 GeV and 46.8 GeV, the total luminosity was 38.3 pb -1 . The liquid argon lead calorimeter of CELLO, the most important part for this analysis, is specialised for the measurement of electromagnetic showers. It has a good space resolution and covers 96% of the solid angle of 4π. We have selected events with 2 photons in the central calorimeter, both with an energy of more than 2 GeV. The high background due to cosmic showers was reduced by accepting only events which were correlated to the time of the e + e - annihilation. Also the direction of the showers had to point to the interaction point. The applied cuts accepted the expected events with a probability P≅0.3. No event was found which was compatible with the production of unstable photinos. One can give limits on the mass of the photino, which depend on the mass of the scalar electron and on the decay path of the photino. In the simplest case, if all photinos decay at the interaction point, photinos with masses below 21 GeV are excluded (with a mass of the scalar electron below 40 GeV). (orig.) [de

γ-unstable nuclei in the sdg boson model

International Nuclear Information System (INIS)

Kuyucak, S.; Lac, V-S.; Morrison, I.; Barret, B.R.

1991-01-01

Following the recent Pt(p,p') experiments which indicated the need for g bosons to reproduce the E4 data, we have extended the O(6) limit of the sd boson model to the sdg bosons. It is shown that a γ-unstable Hamiltonian in the sdg model consisting of a quadrupole interaction and a g boson energy leads to results that are very similar to the O(6) limit. Deviations from the empirical energy spectrum that stem from the γ-unstable nature of the Hamiltonian can be improved by including a consistent hexadecapole interaction which induces triaxiality. The same hexadecapole operator can also account for the strong E4 transitions to the 4 + states presumed to be g boson states. Specific applications are made to the Xe and Pt isotopes. 12 refs., 2 tabs., 4 figs

Metastable and unstable cellular solidification of colloidal suspensions

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Deville, Sylvain; Maire, Eric; Bernard-Granger, Guillaume; Lasalle, Audrey; Bogner, Agnès; Gauthier, Catherine; Leloup, Jérôme; Guizard, Christian

2009-12-01

Colloidal particles are often seen as big atoms that can be directly observed in real space. They are therefore becoming increasingly important as model systems to study processes of interest in condensed-matter physics such as melting, freezing and glass transitions. The solidification of colloidal suspensions has long been a puzzling phenomenon with many unexplained features. Here, we demonstrate and rationalize the existence of instability and metastability domains in cellular solidification of colloidal suspensions, by direct in situ high-resolution X-ray radiography and tomography observations. We explain such interface instabilities by a partial Brownian diffusion of the particles leading to constitutional supercooling situations. Processing under unstable conditions leads to localized and global kinetic instabilities of the solid/liquid interface, affecting the crystal morphology and particle redistribution behaviour.

Coronary artery bypass grafting hemodynamics and anastomosis design: a biomedical engineering review.

Science.gov (United States)

Ghista, Dhanjoo N; Kabinejadian, Foad

2013-12-13

In this paper, coronary arterial bypass grafting hemodynamics and anastomosis designs are reviewed. The paper specifically addresses the biomechanical factors for enhancement of the patency of coronary artery bypass grafts (CABGs). Stenosis of distal anastomosis, caused by thrombosis and intimal hyperplasia (IH), is the major cause of failure of CABGs. Strong correlations have been established between the hemodynamics and vessel wall biomechanical factors and the initiation and development of IH and thrombus formation. Accordingly, several investigations have been conducted and numerous anastomotic geometries and devices have been designed to better regulate the blood flow fields and distribution of hemodynamic parameters and biomechanical factors at the distal anastomosis, in order to enhance the patency of CABGs. Enhancement of longevity and patency rate of CABGs can eliminate the need for re-operation and can significantly lower morbidity, and thereby reduces medical costs for patients suffering from coronary stenosis. This invited review focuses on various endeavors made thus far to design a patency-enhancing optimized anastomotic configuration for the distal junction of CABGs.

Hemodynamic differences between continual positive and two types of negative pressure ventilation.

Science.gov (United States)

Lockhat, D; Langleben, D; Zidulka, A

1992-09-01

In seven anesthetized dogs, ventilated with matching lung volumes, tidal volumes, and respiratory rates, we compared the effects on cardiac output (CO), arterial venous oxygen saturation difference (SaO2 - SVO2), and femoral and inferior vena cava pressure (1) intermittent positive pressure ventilation with positive end-expiratory pressure (CPPV); (2) iron-lung ventilation with negative end-expiratory pressure (ILV-NEEP); (3) grid and wrap ventilation with NEEP applied to the thorax and upper abdomen (G&W-NEEP). The values of CO and SaO2 - SVO2 with ILV-NEEP were similar to those with CPPV. However, with G&W-NEEP as compared with ILV-NEEP, mean CO was greater (2.9 versus 2.6 L/min, p = 0.02) and mean (SaO2 - SVO2) was lower (26.6% versus 28.3%, p = NS). Mean PFEM-IVC was higher with G&W-NEEP than with the other types of ventilation. We conclude that (1) ILV-NEEP is hemodynamically equivalent to CPPV and (2) G&W-NEEP has less adverse hemodynamic consequences. has less adverse hemodynamic consequences.

Renal hemodynamic response to L-dopa during acute renal failure in man

Energy Technology Data Exchange (ETDEWEB)

Zech, P; Collard, M; Guey, A; Plantier, J; Bernard, M; Berthoux, F; Pinet, A; Traeger, J [Hopital Edouard-Herriot, 69 - Lyon (France)

1975-12-20

Twelve patients with acute renal failure underwent L-dopa infusion into a renal artery and /sup 133/Xenon wash-out recordings before and during the infusion. Urine volume and sodium output were also compared during two 24 hours periods, before and after the procedure. Hemodynamic data were compared with data obtained from a matched group of patients receiving Furosemide (8 patients) in place of L-dopa. Only L-dopa infusion significantly increased outer cortical distribution. No blood flow change could be demonstrated in any component nor did the drug improve unitary excretion or the general course of the disease. Control data shows that reduced cortical distribution is the most consistent feature of acute renal failure, so that L-dopa does partially improve intrarenal hemodynamics in this condition. The failure of the drug to restore kidney function may be explained by the following reasons: inability of the agent to restore a normal wash-out pattern: involvment of non-hemodynamic factors, as suggested by comparing similar wash-out improvements after L-dopa in acute glomerulonephritis and in reversible acute renal failure.

Renal hemodynamic response to L-dopa during acute renal failure in man

International Nuclear Information System (INIS)

Zech, P.; Collard, M.; Guey, A.; Plantier, J.; Bernard, M.; Berthoux, F.; Pinet, A.; Traeger, J.

1975-01-01

Twelve patients with acute renal failure underwent L.dopa infusion into a renal artery and 133 Xenon wash-out recordings before and during the infusion. Urine volume and sodium output were also compared during two 24 hours periods, before and after the procedure. Hemodynamic data were compared with data obtained from a matched group of patients receiving Furosemide (8 patients) in place of L.dopa. Only L.dopa infusion significantly increased outer cortical distribution. No blood flow change could be demonstrated in any component nor did the drug improve unitary excretion or the general course of the disease. Control data shows that reduced cortical distribution is the most consistent feature of acute renal failure, so that L.dopa does partially improve intrarenal hemodynamics in this condition. The failure of the drug to restore kidney function may be explained by the following reasons: inability of the agent to restore a normal wash-out pattern: involvment of non-hemodynamic factors, as suggested by comparing similar wash-out improvements after L.dopa in acute glomerulonephritis and in reversible acute renal failure [fr

Multivariate analysis of correlation between electrophysiological and hemodynamic responses during cognitive processing

Science.gov (United States)

Kujala, Jan; Sudre, Gustavo; Vartiainen, Johanna; Liljeström, Mia; Mitchell, Tom; Salmelin, Riitta

2014-01-01

Animal and human studies have frequently shown that in primary sensory and motor regions the BOLD signal correlates positively with high-frequency and negatively with low-frequency neuronal activity. However, recent evidence suggests that this relationship may also vary across cortical areas. Detailed knowledge of the possible spectral diversity between electrophysiological and hemodynamic responses across the human cortex would be essential for neural-level interpretation of fMRI data and for informative multimodal combination of electromagnetic and hemodynamic imaging data, especially in cognitive tasks. We applied multivariate partial least squares correlation analysis to MEG–fMRI data recorded in a reading paradigm to determine the correlation patterns between the data types, at once, across the cortex. Our results revealed heterogeneous patterns of high-frequency correlation between MEG and fMRI responses, with marked dissociation between lower and higher order cortical regions. The low-frequency range showed substantial variance, with negative and positive correlations manifesting at different frequencies across cortical regions. These findings demonstrate the complexity of the neurophysiological counterparts of hemodynamic fluctuations in cognitive processing. PMID:24518260

Pulmonary hemodynamics and gas exchange in off pump coronary artery bypass grafting.

Science.gov (United States)

Vedin, Jenny; Jensen, Ulf; Ericsson, Anders; Samuelsson, Sten; Vaage, Jarle

2005-10-01

To investigate the influence of cardiopulmonary bypass on pulmonary hemodynamics and gas exchange. Low risk patients admitted for elective coronary artery bypass grafting were randomized to either on (n=25) or off pump (n=25) surgery. Central hemodynamics, gas exchange, and venous admixture were studied during and up to 20 h after surgery. There was no difference in pulmonary vascular resistance index (P=0.16), right ventricular stroke work index (P>0.2), mean pulmonary artery pressure (P>0.2) or pulmonary capillary wedge pressure (P>0.2) between groups. Soon after surgery there was a tendency towards higher cardiac index (P=0.07) in the off pump group. Arterial oxygen tension (P>0.2), hematocrit (P>0.2), venous admixture (P>0.2), and arterial-venous oxygen content difference (P=0.12) did not differ between groups. This prospective, randomized study showed no difference in pulmonary hemodynamics, pulmonary gas exchange, and venous admixture, in low risk patients undergoing off pump compared to on pump coronary artery bypass surgery.

Energy harvesting by dynamic unstability and internal resonance for piezoelectric beam

Energy Technology Data Exchange (ETDEWEB)

Lan, Chunbo; Qin, Weiyang, E-mail: 353481781@qq.com; Deng, Wangzheng [Department of Engineering Mechanics, Northwestern Polytechnical University, Xi' an 710072 (China)

2015-08-31

We investigated the energy harvesting of a vertical beam with tip mass under vertical excitations. We applied dynamic unstability and internal resonance to improve the efficiency of harvesting. The experiments of harmonic excitation were carried out. Results show that for the beam there exist internal resonances in the dynamically unstable and the buckling bistable cases. The dynamic unstability is a determinant for strong internal resonance or mode coupling, which can be used to create a large output from piezoelectric patches. Then, the experiments of stochastic excitation were carried out. Results prove that the internal resonance or mode coupling can transfer the excitation energy to the low order modes, mainly the first and the second one. This can bring about a large output voltage. For a stochastic excitation, it is proved that there is an optimal weight of tip mass for realizing internal resonance and producing large outputs.

Vascular Adaptation to Exercise in Humans: Role of Hemodynamic Stimuli

Science.gov (United States)

Green, Daniel J.; Hopman, Maria T. E.; Padilla, Jaume; Laughlin, M. Harold; Thijssen, Dick H. J.

2017-01-01

On the 400th anniversary of Harvey's Lumleian lectures, this review focuses on “hemodynamic” forces associated with the movement of blood through arteries in humans and the functional and structural adaptations that result from repeated episodic exposure to such stimuli. The late 20th century discovery that endothelial cells modify arterial tone via paracrine transduction provoked studies exploring the direct mechanical effects of blood flow and pressure on vascular function and adaptation in vivo. In this review, we address the impact of distinct hemodynamic signals that occur in response to exercise, the interrelationships between these signals, the nature of the adaptive responses that manifest under different physiological conditions, and the implications for human health. Exercise modifies blood flow, luminal shear stress, arterial pressure, and tangential wall stress, all of which can transduce changes in arterial function, diameter, and wall thickness. There are important clinical implications of the adaptation that occurs as a consequence of repeated hemodynamic stimulation associated with exercise training in humans, including impacts on atherosclerotic risk in conduit arteries, the control of blood pressure in resistance vessels, oxygen delivery and diffusion, and microvascular health. Exercise training studies have demonstrated that direct hemodynamic impacts on the health of the artery wall contribute to the well-established decrease in cardiovascular risk attributed to physical activity. PMID:28151424

Infrared sensitivity of unstable vacua

International Nuclear Information System (INIS)

Krotov, Dmitry; Polyakov, Alexander M.

2011-01-01

We discover that some unstable vacua have long memory. By that we mean that even in the theories containing only massive particles, there are correllators and expectation values which grow with time. We examine the cases of instabilities caused by the constant electric fields, expanding and contracting universes and, most importantly, the global de Sitter space. In the last case the interaction leads to a remarkable UV/IR mixing and to a large back reaction. This gives reasons to believe that the cosmological constant problem could be resolved by the infrared physics.

Improving hemodynamics of cardiovascular system under a novel intraventricular assist device support via modeling and simulations.

Science.gov (United States)

Zhu, Shidong; Luo, Lin; Yang, Bibo; Li, Xinghui; Wang, Xiaohao

2017-12-01

Ventricular assist devices (LVADs) are increasingly recognized for supporting blood circulation in heart failure patients who are non-transplant eligible. Because of its volume, the traditional pulsatile device is not easy to implant intracorporeally. Continuous flow LVADs (CF-LVADs) reduce arterial pulsatility and only offer continuous flow, which is different from physiological flow, and may cause long-term complications in the cardiovascular system. The aim of this study was to design a new pulsatile assist device that overcomes this disadvantage, and to test this device in the cardiovascular system. Firstly, the input and output characteristics of the new device were tested in a simple cardiovascular mock system. A detailed mathematical model was established by fitting the experimental data. Secondly, the model was tested in four pathological cases, and was simulated and coupled with a fifth-order cardiovascular system and a new device model using Matlab software. Using assistance of the new device, we demonstrated that the left ventricle pressure, aortic pressure, and aortic flow of heart failure patients improved to the levels of a healthy individual. Especially, in state IV level heart failure patients, the systolic blood pressure increased from 81.34 mmHg to 132.1 mmHg, whereas the diastolic blood pressure increased from 54.28 mmHg to 78.7 mmHg. Cardiac output increased from 3.21 L/min to 5.16 L/min. The newly-developed assist device not only provided a physiological flow that was similar to healthy individuals, but also effectively improved the ability of the pathological ventricular volume. Finally, the effects of the new device on other hemodynamic parameters are discussed.

Hemodynamic effects of 6% hydroxyethyl starch infusion in sevoflurane-anesthetized thoroughbred horses.

Science.gov (United States)

Ohta, Minoru; Kurimoto, Shinjiro; Tokushige, Hirotaka; Kuroda, Taisuke; Ishikawa, Yuhiro

2013-07-31

To determine hemodynamic effects of hydroxyethyl starch (HES) infusion during anesthesia in horses, incremental doses of 6% HES were administered to 6 healthy Thoroughbred horses. Anesthesia was induced with xylazine, guaifenesin and thiopental and maintained with sevoflurane at 2.8% of end-tidal concentration in all horses. The horses were positioned in right lateral recumbency and administered 3 intravenous dose of 6% HES (5 ml/kg) over 15 min with 15-min intervals in addition to constant infusion of lactated Ringer's solution at 10 ml/kg/hr. Hemodynamic parameters were measured before and every 15 min until 90 min after the administration of 6% HES. There was no significant change in heart rate and arterial blood pressures throughout the experiment. The HES administration produced significant increases in mean right atrial pressure, stroke volume, cardiac output (CO) and decrease in systemic vascular resistance (SVR) in a dose-dependent manner. There was no significant change in electrolytes (Na(+), K(+), Cl(-)) throughout the experiment, however, packed cell volume, hemoglobin concentration, and total protein and albumin concentrations decreased in a dose-dependent manner following the HES administration. In conclusion, the HES administration provides a dose-dependent increase in CO, but has no impact upon arterial blood pressures due to a simultaneous decrease in SVR.

Concluding remarks of the International symposium on structure and reactions of unstable nuclei

International Nuclear Information System (INIS)

Mueller, A.C.

1991-01-01

A brief history of unstable beams is given, followed by a short description of the experimental facilities. The structure and reaction of unstable nuclei is discussed, and the neutron-halo nuclei are studied. Some considerations are given related to exotic-beam facilities. (K.A.) 14 refs., 2 figs

Art care: A multi-modality coronary 3D reconstruction and hemodynamic status assessment software.

Science.gov (United States)

Siogkas, Panagiotis K; Stefanou, Kostas A; Athanasiou, Lambros S; Papafaklis, Michail I; Michalis, Lampros K; Fotiadis, Dimitrios I

2018-01-01

Due to the incremental increase of clinical interest in the development of software that allows the 3-dimensional (3D) reconstruction and the functional assessment of the coronary vasculature, several software packages have been developed and are available today. Taking this into consideration, we have developed an innovative suite of software modules that perform 3D reconstruction of coronary arterial segments using different coronary imaging modalities such as IntraVascular UltraSound (IVUS) and invasive coronary angiography images (ICA), Optical Coherence Tomography (OCT) and ICA images, or plain ICA images and can safely and accurately assess the hemodynamic status of the artery of interest. The user can perform automated or manual segmentation of the IVUS or OCT images, visualize in 3D the reconstructed vessel and export it to formats, which are compatible with other Computer Aided Design (CAD) software systems. We employ finite elements to provide the capability to assess the hemodynamic functionality of the reconstructed vessels by calculating the virtual functional assessment index (vFAI), an index that corresponds and has been shown to correlate well to the actual fractional flow reserve (FFR) value. All the modules of the proposed system have been thoroughly validated. In brief, the 3D-QCA module, compared to a successful commercial software of the same genre, presented very good correlation using several validation metrics, with a Pearson's correlation coefficient (R) for the calculated volumes, vFAI, length and minimum lumen diameter of 0.99, 0.99, 0.99 and 0.88, respectively. Moreover, the automatic lumen detection modules for IVUS and OCT presented very high accuracy compared to the annotations by medical experts with the Pearson's correlation coefficient reaching the values of 0.94 and 0.99, respectively. In this study, we have presented a user-friendly software for the 3D reconstruction of coronary arterial segments and the accurate hemodynamic

Development and evaluation of totally implantable ventricular assist system using a vibrating flow pump and transcutaneous energy transmission system with amorphous fibers.

Science.gov (United States)

Yambe, T; Hashimoto, H; Kobayashi, S; Sonobe, T; Naganuma, S; Nanka, S S; Matsuki, H; Yoshizawa, M; Tabayashi, K; Takayasu, H; Takeda, H; Nitta, S

1997-01-01

We have developed a vibrating flow pump (VFP) that can generate oscillated blood flow with a relatively high frequency (10-50 Hz) for a totally implantable ventricular assist system (VAS). To evaluate the newly developed VAS, left heart bypasses, using the VFP, were performed in chronic animal experiments. Hemodynamic parameters were recorded in a data recorder in healthy adult goats during an awake condition and analyzed in a personal computer system through an alternating-direct current converter. Basic performance of the total system with a transcutaneous energy transmission system were satisfactory. During left ventricular assistance with the VFP, Mayer wave fluctuations of hemodynamics were decreased in the power spectrum, the fractal dimensions of the hemodynamics were significantly decreased, and peripheral vascular resistance was significantly decreased. These results suggest that cardiovascular regulatory nonlinear dynamics, which mediate the hemodynamics, may be affected by left ventricular bypass with oscillated flow. The decreased power of the Mayer wave in the spectrum caused the limit cycle attractor of the hemodynamics and decreased peripheral resistance. These results suggest that this newly developed VAS is useful for the totally implantable system with unique characteristics that can control hemodynamic properties.

Synchronizing movements with the metronome: nonlinear error correction and unstable periodic orbits.

Science.gov (United States)

Engbert, Ralf; Krampe, Ralf Th; Kurths, Jürgen; Kliegl, Reinhold

2002-02-01

The control of human hand movements is investigated in a simple synchronization task. We propose and analyze a stochastic model based on nonlinear error correction; a mechanism which implies the existence of unstable periodic orbits. This prediction is tested in an experiment with human subjects. We find that our experimental data are in good agreement with numerical simulations of our theoretical model. These results suggest that feedback control of the human motor systems shows nonlinear behavior. Copyright 2001 Elsevier Science (USA).

Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed Flames

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Zuo-Yu Sun

2014-07-01

Full Text Available Buoyant unstable behavior in initially spherical lean hydrogen-air premixed flames within a center-ignited combustion vessel have been studied experimentally under a wide range of pressures (including reduced, normal, and elevated pressures. The experimental observations show that the flame front of lean hydrogen-air premixed flames will not give rise to the phenomenon of cellular instability when the equivalence ratio has been reduced to a certain value, which is totally different from the traditional understanding of the instability characteristics of lean hydrogen premixed flames. Accompanied by the smoothened flame front, the propagation mode of lean hydrogen premixed flames transitions from initially spherical outwardly towards upwardly when the flames expand to certain sizes. To quantitatively investigate such buoyant instability behaviors, two parameters, “float rate (ψ” and “critical flame radius (Rcr”, have been proposed in the present article. The quantitative results demonstrate that the influences of initial pressure (Pint on buoyant unstable behaviors are different. Based on the effects of variation of density difference and stretch rate on the flame front, the mechanism of such buoyant unstable behaviors has been explained by the competition between the stretch force and the results of gravity and buoyancy, and lean hydrogen premixed flames will display buoyant unstable behavior when the stretch effects on the flame front are weaker than the effects of gravity and buoyancy.

The Value of Quality Improvement Process in the Detection and Correction of Common Errors in Echocardiographic Hemodynamic Parameters in a Busy Echocardiography Laboratory.

Science.gov (United States)

Fanari, Zaher; Choudhry, Usman I; Reddy, Vivek K; Eze-Nliam, Chete; Hammami, Sumaya; Kolm, Paul; Weintraub, William S; Marshall, Erik S

2015-12-01

Accurate assessment of cardiac structures, ventricular function, and hemodynamics is essential for any echocardiographic laboratory. Quality improvement (QI) processes described by the American Society of Echocardiography (ASE) and the Intersocietal Commission (IAC) should be instrumental in reaching this goal. All patients undergoing transthoracic echocardiogram (TTE) followed by cardiac catheterization within 24 hours at Christiana Care Health System in 2011 and 2012 were identified, with 126 and 133 cases, respectively. Hemodynamic parameters of diastolic function and pulmonary artery systolic pressure (PASP) on TTE correlated poorly with catheterization in 2011. An educational process was developed and implemented at quarterly QI meetings based on ASE and IAC recommendations to target frequently encountered errors and provide methods for improved performance. The hemodynamic parameters were then reexamined in 2012 postintervention. Following the QI process, there was significant improvement in the correlation between invasive and echocardiographic hemodynamic measurements in both systolic and diastolic function, and PASP. This reflected in significant better correlations between echo and cath LVEF [R = 0.88, ICC = 0.87 vs. R = 0.85, ICC = 0.85; P process, as recommended by ASE and IAC, can allow for identification as well as rectification of quality issues in a large regional academic medical center hospital. © 2015, Wiley Periodicals, Inc.

Correction of Hemodynamic Disorders in the Complex Surgical Correction of Acquired Cardiac Valvular Defects

Directory of Open Access Journals (Sweden)

A. I. Lenkin

2011-01-01

Full Text Available Objective: to compare the efficiency of using the values of transpulmonary (PiCCO and prepulmonary (Swan-Ganz catheter thermodilution as guides to targeted therapy for hemodynamic disorders in the surgical correction of mixed cardiac valvular defects. Subjects and methods. The study enrolled 40 patients operated on for acquired cardiac diseases who were randomized to two matched groups. Hemodynamics was monitored by means of a Swan-Ganz catheter in Group 1 and by transpulmonary thermodilution in Group 2. Anesthesia was maintained with propofol and fentanyl. Infusion therapy was performed using crystalloid and colloid solutions. Continuous intravenous infusion of inotropic agents was used when heart failure was developed. Hemodynamic, clinical, and laboratory parameters were estimated intraoperatively and within 24 hours postoperatively. Results. The groups did not differ in the degree of baseline heart failure, the duration of an operation and myocardial ischemia, and the length of extracorporeal circulation. In the PiCCO group, postoperative infusion volume was 33% higher than that in the Swan-Ganz group, which ensured increases in stroke volume and oxygen delivery in the early postoperative period (p<0.05. Respiratory support was 26% shorter in the PiCCO group (p<0.04. Conclusion. After surgical interventions for mixed cardiac defects, the targeted therapy algorithm based on transpulmonary thermodilution provided more steady-state values of hemodynamics and oxygen transport, which was followed by the increased scope of infusion therapy and the shorter length of postoperative mechanical ventilation than that based on hemodynamics being corrected from the values of prepul-monary thermodilution. Key words: transpulmonary thermodilution, targeted therapy, prepulmonary ther-modilution, acquired heart disease.

Association between hemodynamic modifications and clinical outcome of intracranial aneurysms treated using flow diverters.

Science.gov (United States)

Paliwal, Nikhil; Damiano, Robert J; Davies, Jason M; Siddiqui, Adnan H; Meng, Hui

2017-02-11

Treatment of intracranial aneurysms (IAs) has been revolutionized by the advent of endovascular Flow Diverters (FDs), which disrupt blood flow within the aneurysm to induce pro-thrombotic conditions, and serves as a scaffold for endothelial ingrowth and arterial remodeling. Despite good clinical success of FDs, complications like incomplete occlusion and post-treatment rupture leading to subarachnoid hemorrhage have been reported. In silico computational fluid dynamic analysis of the pre- and post-treated geometries of IA patients can shed light on the contrasting blood hemodynamics associated with different clinical outcomes. In this study, we analyzed hemodynamic modifications in 15 IA patients treated using a single FD; 10 IAs were completely occluded (successful) and 5 were partially occluded (unsuccessful) at 12-month follow-up. An in-house virtual stenting workflow was used to recapitulate the clinical intervention on these cases, followed by CFD to obtain pre- and post-treatment hemodynamics. Bulk hemodynamic parameters showed comparable reductions in both groups with average inflow rate and aneurysmal velocity reduction of 40.3% and 52.4% in successful cases, and 34.4% and 49.2% in unsuccessful cases. There was a substantial reduction in localized parameter like vortex coreline length and Energy Loss for successful cases, 38.2% and 42.9% compared to 10.1% and 10.5% for unsuccessful cases. This suggest that for successfully treated IAs, the localized complex blood flow is disrupted more prominently by the FD as compared to unsuccessful cases. These localized hemodynamic parameters can be potentially used in prediction of treatment outcome, thus aiding the clinicians in a priori assessment of different treatment strategies.

Accelerator complex for unstable beams at INS

International Nuclear Information System (INIS)

Tomizawa, M.; Arai, S.; Doi, M.; Katayama, T.; Niki, K.; Tokuda, N.; Yoshizawa, M.

1992-11-01

The construction of the prototype facility of the Exotic arena in the Japan Hadron Project (JHP) is started in 1992 at the Institute for Nuclear Study (INS), University of Tokyo. The purpose of this facility is to study the various technical problems of the Exotic arena, and to perform the experiment on nuclear and astrophysics with unstable nuclear beam. The unstable nuclei produced by bombarding a thick target with 40 MeV proton beam from the existing SF cyclotron are ionized in the ion sources, mass-analyzed by an ISOL, and transported to the accelerator complex. The accelerator complex consists of a split coaxial RFQ and an interdigital H type linac. The construction of accelerator will be completed in fiscal year 1994. The development of the SCRFQ and the IH linac which is suitable to the post-accelerator of the SCRFQ are reported. Charge stripper and the beam matching between the SCRFQ and the IH linac are explained. A buncher is necessary for the matching of longitudinal phase space between the SCRFQ and the IH linac. (K.I.)

Low-dose esmolol: hemodynamic response to endotracheal intubation in normotensive patients

Directory of Open Access Journals (Sweden)

Suresh Lakshmanappa

2012-06-01

Full Text Available Abstract Purpose: Endotracheal intubation is a frequently utilized and highly invasive component of anesthesia that is often accompanied by potentially harmful hemodynamic pressor responses. The purpose of this study was to investigate the efficiency of a single pre-induction 1 mg/kg bolus injection of esmolol for attenuating these hemodynamic responses to endotracheal intubation in normotensive patients. Material and methods: The study was composed of 100 randomly selected male and female patients between the ages of 18 and 60 that were scheduled for elective surgery and belonged to ASA grade I or II. Two minutes prior to intubation the control group received 10 mL of saline (n=50 and the experimental group received an injection of esmolol 1 mg/kg diluted to 10 mL (n=50. Heart rate (HR, systolic blood pressure (SBP, diastolic blood pressure (DBP, mean arterial pressure (MAP, and rate pressure product (RPP were compared to basal values before receiving medication (T-0, during pre-induction (T-1, induction (T-2, intubation (T-3, and post-intubation at 1 (T-4, 3 (T-6, 5 (T-8, and 10 (T-13 minutes. Results: Esmolol significantly attenuated the hemodynamic responses to endotracheal intubation at the majority of measured points. Attenuation of HR (10.8%, SBP (7.04%, DBP (3.99%, MAP (5%, and RPP (16.9% was observed in the esmolol group when compared to the control group values. Conclusions: A single pre-induction 1 mg/kg bolus injection of esmolol successfully attenuated the hemodynamic pressor response in normotensive patients. A significant attenuation of heart rate, systolic blood pressure, diastolic blood pressure and mean arterial pressure was observed at the majority of measured time points in the esmolol administered group compared to the control group. [J Contemp Med 2012; 2(2.000: 69-76

Seismic monitoring of the unstable rock slope at Aaknes, Norway

Science.gov (United States)

Roth, M.; Blikra, L. H.

2009-04-01

The unstable rock slope at Aaknes has an estimated volume of about 70 million cubic meters, and parts of the slope are moving at a rate between 2-15 cm/year. Amongst many other direct monitoring systems we have installed a small-scale seismic network (8 three-component geophones over an area of 250 x 150 meters) in order to monitor microseismic events related to the movement of the slope. The network has been operational since November 2005 with only a few short-term outages. Seismic data are transferred in real-time from the site to NORSAR for automatic detection processing. The resulting detection lists and charts and the associated waveform are forwarded immediately to the early warning centre of the Municipality of Stranda. Furthermore, we make them available after a delay of about 10-15 minutes on our public project web page (http://www.norsar.no/pc-47-48-Latest-Data.aspx). Seismic monitoring provides independent and complementary data to the more direct monitoring systems at Aaknes. We observe increased seismic activity in periods of heavy rain fall or snow melt, when laser ranging data and extensometer readings indicate temporary acceleration phases of the slope. The seismic network is too small and the velocity structure is too heterogeneous in order to obtain reliable localizations of the microseismic events. In summer 2009 we plan to install a high-sensitive broadband seismometer (60 s - 100 Hz) in the middle of the unstable slope. This will allow us to better constrain the locations of the microseismic events and to investigate potential low-frequency signals associated with the slope movement.

Clinical Course of Two Children with Unstable Hemoglobins : The Effect of Hydroxyurea Therapy

NARCIS (Netherlands)

Loovers, Harriet M.; Tamminga, Nienke; Mulder, Andre B.; Tamminga, Rienk Y. J.

Case reports on the effect of hydroxyurea (HU) therapy for unstable hemoglobins (Hbs) are sparse; only three adult cases have been reported. We report for the first time on the effect of HU therapy in children carrying unstable Hbs. The first case concerns a female child with a familial history of

Effect of an Unstable Load on Primary and Stabilizing Muscles During the Bench Press.

Science.gov (United States)

Ostrowski, Stephanie J; Carlson, Lara A; Lawrence, Michael A

2017-02-01

Ostrowski, SJ, Carlson, LA, and Lawrence, MA. Effect of an unstable load on primary and stabilizing muscles during the bench press. J Strength Cond Res 31(2): 430-434, 2017-Unstable resistance exercises are performed to increase activity of stabilizing muscles. The premise is that this increase in activity will yield greater strength gains than traditional resistance exercises. The purpose of this study was to determine if an unstable load increases muscle activity of stabilizing muscles during a bench press as compared with a standard bench press with a typical load. Fifteen resistance-trained males (age 24.2 ± 2.7 years, mass 84.8 ± 12.0 kg, height 1.77 ± 0.05 m, weight lifting experience 9.9 ± 3.4 years, and bench press 1 repetition maximum [1RM] 107.5 ± 25.9 kg) volunteered for this study. Subjects pressed 2 sets of 5 repetitions in both stable (75% 1RM) and unstable (60% 1RM) conditions using a standard barbell and a flexible Earthquake bar, respectively. Surface electromyography was used to detect muscle activity of primary movers (pectoralis major, anterior deltoid, and triceps) and stabilizing musculature (latissimus dorsi, middle and posterior deltoid, biceps brachii, and upper trapezius). Muscle activity was compared using a multivariate analysis of variance to determine significant (p ≤ 0.05) phase and condition differences. The right and left biceps and the left middle deltoid were significantly more active in the unstable condition. Some of the stabilizing muscles were found to be significantly more active in the unstable condition with 15% less weight. Therefore, bench pressing with an unstable load appears promising in activating stabilizing musculature compared with pressing a typical barbell.

On the Fate of Unstable Circumbinary Planets: Tatooine’s Close Encounters with a Death Star

Science.gov (United States)

Sutherland, Adam P.; Fabrycky, Daniel C.

2016-02-01

Circumbinary planets whose orbits become unstable may be ejected, accreted, or even captured by one of the stars. We quantify the relative rates of these channels, for a binary of secondary star’s mass fraction 0.1 with an orbit of 1 AU. The most common outcome is ejection, which happens ∼80% of the time. If binary systems form circumbinary planets readily and sloppily, this process may fill the Milky Way with free-floating planets. A significant fraction of the time, ∼20%, the unstable planet strikes the primary or secondary. We tracked whether a Jupiter-like planet would undergo tidal stripping events during close passages, and find that these events are rarely strong enough to capture the planet, although this may be observable via free-floating planets that are heated or spun-up by this process.

Considerations concering the generalization of the Dirac equations to unstable fermions

International Nuclear Information System (INIS)

Kniehl, Bernd A.; Sirlin, Alberto

2014-08-01

We discuss the generalization of the Dirac equations and spinors in momentum space to free unstable spin-1/2 fermions taking into account the fundamental requirement of Lorentz covariance. We derive the generalized adjoint Dirac equations and spinors, and explain the very simple relation that exists, in our formulation, between the unstable and stable cases. As an application of the generalized spinors, we evaluate the probability density. We also discuss the behavior of the generalized Dirac equations under time reversal.

Intravenous vs. left ventricular injection of ionic contrast material: hemodynamic implications for digital subtraction angiography

International Nuclear Information System (INIS)

Mancini, G.B.; Ostrander, D.R.; Slutsky, R.A.; Shabetai, R.; Higgins, C.B.

1983-01-01

Because of the increased use of intravenous injection of contrast material for the evaluation of cardiac structure and function by digital subtraction techniques, a study was done to assess the hemodynamic effects of contrast material when used in this fashion in man. In 10 patients, with each serving as his own control, the effects of intravenous and intraventricular injections of sodium meglumine diatrizoate (Renografin 76) in the same dose were compared. There was no difference between these two methods with respect to changes in pulmonary wedge pressures, systemic pressures, and pulmonary vascular resistance. The elevation of mean pulmonary artery and right atrial pressure was greater after the intraventricular injection (p <0.05). The elevated cardiac output and systemic vascular resistance returned to control values somewhat more quickly after the intravenous injection (p<0.001 and p<0.05, respectively); and the increase in cardiac output was greater after the intravenous injection at 1 min (p<0.05), but less than after the intraventricular injection at 2 min (p<0.05). Despite the detection of these statistically significant differences, the magnitude and timing of these differences are too small to justify the notion that imaging by intravenous injections of standard ionic contrast media provides any substantial hemodynamic benefits or decreased risk to the patient

Minimal gain marching schemes: searching for unstable steady-states with unsteady solvers

Science.gov (United States)

de S. Teixeira, Renan; S. de B. Alves, Leonardo

2017-12-01

Reference solutions are important in several applications. They are used as base states in linear stability analyses as well as initial conditions and reference states for sponge zones in numerical simulations, just to name a few examples. Their accuracy is also paramount in both fields, leading to more reliable analyses and efficient simulations, respectively. Hence, steady-states usually make the best reference solutions. Unfortunately, standard marching schemes utilized for accurate unsteady simulations almost never reach steady-states of unstable flows. Steady governing equations could be solved instead, by employing Newton-type methods often coupled with continuation techniques. However, such iterative approaches do require large computational resources and very good initial guesses to converge. These difficulties motivated the development of a technique known as selective frequency damping (SFD) (Åkervik et al. in Phys Fluids 18(6):068102, 2006). It adds a source term to the unsteady governing equations that filters out the unstable frequencies, allowing a steady-state to be reached. This approach does not require a good initial condition and works well for self-excited flows, where a single nonzero excitation frequency is selected by either absolute or global instability mechanisms. On the other hand, it seems unable to damp stationary disturbances. Furthermore, flows with a broad unstable frequency spectrum might require the use of multiple filters, which delays convergence significantly. Both scenarios appear in convectively, absolutely or globally unstable flows. An alternative approach is proposed in the present paper. It modifies the coefficients of a marching scheme in such a way that makes the absolute value of its linear gain smaller than one within the required unstable frequency spectra, allowing the respective disturbance amplitudes to decay given enough time. These ideas are applied here to implicit multi-step schemes. A few chosen test cases

Relationship between the serologic status of helicobacter pylori with the presence of unstable angina

International Nuclear Information System (INIS)

Alavi, S.M.; Adel, S. M. H.; Rajabzadeh, A.

2008-01-01

To determine whether unstable angina is co-related to seropositivity to chronic Helicobacter pylori (HP) infection. It is a case control, descriptive study conducted at CCU in Razi Hospital in Ahwaz a city southwest Iran, from 2004 to 2005. We measured serum HP- lgG levels of participants in CCU in a hospital. Blood samples were drawn during study period from 96 patients (mean age 56 years) with Unstable Angina (UA) according to American Heart Association criteria and from 96 participants free of cardiovascular disease (mean age 58 years) and stored at 20 degree C. Serology results were studied in relation to UA. Using chi squared test, odds ratios (OR) and 95% confidence intervals (CI) were calculated, adjusting for age, gender, and established risk factors. Seventy nine (82.3%) of patients with unstable angina and 55(61.1%) in the control group presented a positive anti HP-lgG. Odds ratio was 3 with 95% CI: 1.9 to 4.3. There was significant relation between HP-lgG positivity and unstable angina (P 0.05). Our study revealed relationship between seropositivity of HP-lgG and unstable angina. (author)

Orbit dynamics for unstable linear motion

International Nuclear Information System (INIS)

Parzen, G.

1997-01-01

A treatment is given of the orbit dynamics for linear unstable motion that allows for the zeros in the beta function and makes no assumptions about the realness of the betatron and phase functions. The phase shift per turn is shown to be related to the beta function and the number of zeros the beta function goes through per turn. The solutions of the equations of motion are found in terms of the beta function

Orbit dynamics for unstable linear motion

International Nuclear Information System (INIS)

Parzen, G.

1996-04-01

A treatment is given of the orbit dynamics for linear unstable motion that allows for the zeros in the beta function and makes no assumption about the realness of the betatron and phase functions. The phase shift per turn is shown to be related to the beta function and the number of zeros the beta function goes through per turn. The solutions of the equations of motion are found in terms of the beta function

Detection of unstable angina by /sup 99m/technetium pyrophosphate myocardial scintigraphy

International Nuclear Information System (INIS)

Abdulla, A.M.; Canedo, M.I.; Cortez, B.C.; McGinnis, K.D.; Wilhelm, S.K.

1976-01-01

/sup 99m/Technetium stannous pyrophosphate has been shown to accumulate in acutely infarcted myocardium. To determine if the isotope is also taken up by severely ischemic, but not necrotic myocardium, we performed myocardial scintigraphic studies in 17 patients with chest pains. Seven of the patients satisfied conventional clinical, electrocardiographic, and laboratory criteria for the diagnosis of unstable angina and showed no electrocardiographic or enzymatic evidence of myocardial necrosis. Five of these seven patients with unstable angina demonstrated abnormal localized patterns, and one showed a borderline picture. Myocardial scintiscans were normal in all of a control group of ten patients with stable angina. Thus, scanning with /sup 99m/technetium stannous pyrophosphate is shown to be of value in the objective demonstration of myocardial abnormality in unstable angina

Unstable Periodic Orbit Analysis of Histograms of Chaotic Time Series

International Nuclear Information System (INIS)

Zoldi, S.M.

1998-01-01

Using the Lorenz equations, we have investigated whether unstable periodic orbits (UPOs) associated with a strange attractor may predict the occurrence of the robust sharp peaks in histograms of some experimental chaotic time series. Histograms with sharp peaks occur for the Lorenz parameter value r=60.0 but not for r=28.0 , and the sharp peaks for r=60.0 do not correspond to a histogram derived from any single UPO. However, we show that histograms derived from the time series of a non-Axiom-A chaotic system can be accurately predicted by an escape-time weighting of UPO histograms. copyright 1998 The American Physical Society

Genesis and bifurcations of unstable periodic orbits in a jet flow

International Nuclear Information System (INIS)

Uleysky, M Yu; Budyansky, M V; Prants, S V

2008-01-01

We study the origin and bifurcations of typical classes of unstable periodic orbits in a jet flow that was introduced before as a kinematic model of chaotic advection, transport and mixing of passive scalars in meandering oceanic and atmospheric currents. A method to detect and locate the unstable periodic orbits and classify them by the origin and bifurcations is developed. We consider in detail period-1 and period-4 orbits playing an important role in chaotic advection. We introduce five classes of period-4 orbits: western and eastern ballistic ones, whose origin is associated with ballistic resonances of the fourth-order, rotational ones, associated with rotational resonances of the second and fourth orders and rotational-ballistic ones associated with a rotational-ballistic resonance. It is a new kind of unstable periodic orbits that may appear in a chaotic flow with jets and/or circulation cells. Varying the perturbation amplitude, we track out the origin and bifurcations of the orbits for each class

Spinal instrumentation for unstable C1-2 injury.

Science.gov (United States)

Mizuno, J; Nakagawa, H

1999-06-01

Seventeen patients with unstable C1-2 injuries were treated between 1990 and 1997. Various methods of instrumentation surgery were performed in 16 patients, excluding a case of atlantoaxial rotatory fixation. Posterior stabilization was carried out in 14 cases using Halifax interlaminar clamp, Sof'wire or Danek cable, or more recently, transarticular screws. Transodontoid anterior screw fixation was performed in four cases of odontoid process fractures, with posterior instrumentation in two cases because of malunion. Rigid internal fixation by instrumentation surgery for the unstable C1-2 injury avoids long-term application of a Halo brace and facilitates early rehabilitation. However, the procedure is technically demanding with the risk of neural and vascular injuries, particularly with posterior screw fixation. Sagittal reconstruction of thin-sliced computed tomography scans at the C1-2 region, neuronavigator, and intraoperative fluoroscopy are essential to allow preoperative surgical planning and intraoperative guidance.

On matrix stabilisation of d- and f-transition metal ions in unstable oxidation states

Energy Technology Data Exchange (ETDEWEB)

Kiselev, Yurii M [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2009-01-31

The state-of-the-art in matrix stabilisation of d- and f-transition metal ions in unstable oxidation states is analysed. Main aspects of this problem concerning the genealogy of appropriate matrix systems are classified. Relevant examples are given and the data that contradict the scheme proposed are discussed. The thermodynamics of the matrix stabilisation effect is considered using the concept of isomorphic miscibility. The influence of defects and non-equilibrium on the matrix stabilisation effect is discussed. The problem of identification of the oxidation states in matrix systems is examined and various types of matrix systems are considered.

On matrix stabilisation of d- and f-transition metal ions in unstable oxidation states

International Nuclear Information System (INIS)

Kiselev, Yurii M

2009-01-01

The state-of-the-art in matrix stabilisation of d- and f-transition metal ions in unstable oxidation states is analysed. Main aspects of this problem concerning the genealogy of appropriate matrix systems are classified. Relevant examples are given and the data that contradict the scheme proposed are discussed. The thermodynamics of the matrix stabilisation effect is considered using the concept of isomorphic miscibility. The influence of defects and non-equilibrium on the matrix stabilisation effect is discussed. The problem of identification of the oxidation states in matrix systems is examined and various types of matrix systems are considered.

Hemodynamic effects of innominate artery occlusive disease on anterior cerebral artery.

Science.gov (United States)

Tan, Teng-Yeow; Lien, Li-Ming; Schminke, Ulf; Tesh, Paul; Reynolds, Patrick S; Tegeler, Charles H

2002-01-01

Stenoses of the innominate artery (IA) may affect flow conditions in the carotid arteries. However, alternating flow in ipsilateral anterior cerebral artery (ACA) due to IA stenosis is extremely rare. A 49-year-old woman who was evaluated for symptomatic cerebrovascular disease presented with right latent subclavian and right carotid system steal. Transcranial Doppler examination displayed systolic deceleration wave-forms in the right terminal internal carotid artery and alternating flow in the right ACA. Magnetic resonance angiography demonstrated tight stenosis of the right IA. For a thorough study of the hemodynamic effects of IA stenosis, a combination of duplex and transcranial Doppler examination is required.

Central Hemodynamics Measured During 5 Repetition Maximum Free Weight Resistance Exercise.

Science.gov (United States)

Howard, Jonathan S; McLester, Cherilyn N; Evans, Thomas W; McLester, John R; Calloway, Jimmy P

2018-01-01

The PhysioFlow™ is a piece of equipment that uses bioimpedance cardiography to measure central hemodynamics. The purpose of this research was to explore the novel approach of monitoring central hemodynamics during free weight resistance exercise using bioimpedance cardiography throughout a 5 repetition maximum (5RM). Thirty participants ranging from beginner to advanced lifters (16 males and 14 females) completed a 5RM for back squat, seated push press, and bicep curl while connected to the PhysioFlow™ to assess the response of heart rate (HR), stroke volume (SV), cardiac output (Q), and ejection fraction (EF). Participants were cued for form and to breathe normally throughout the lifts. The PhysioFlow™ detected an increase in HR and Q for all lifts between rest and each repetition ( p 0.05) and no changes in EF or SV were detected when all repetitions were compared to each other for all lifts ( p > 0.05). In conclusion, the PhysioFlow™ was able to detect changes in HR and Q during dynamic free weight resistance exercise. This novel approach may provide a mechanism for monitoring central hemodynamics during free weight resistance training. However, more research needs to be conducted as the exercise protocol for this investigation did not allow for a comparison to a reference method.

Automatic Detection and Visualization of Qualitative Hemodynamic Characteristics in Cerebral Aneurysms.

Science.gov (United States)

Gasteiger, R; Lehmann, D J; van Pelt, R; Janiga, G; Beuing, O; Vilanova, A; Theisel, H; Preim, B

2012-12-01

Cerebral aneurysms are a pathological vessel dilatation that bear a high risk of rupture. For the understanding and evaluation of the risk of rupture, the analysis of hemodynamic information plays an important role. Besides quantitative hemodynamic information, also qualitative flow characteristics, e.g., the inflow jet and impingement zone are correlated with the risk of rupture. However, the assessment of these two characteristics is currently based on an interactive visual investigation of the flow field, obtained by computational fluid dynamics (CFD) or blood flow measurements. We present an automatic and robust detection as well as an expressive visualization of these characteristics. The detection can be used to support a comparison, e.g., of simulation results reflecting different treatment options. Our approach utilizes local streamline properties to formalize the inflow jet and impingement zone. We extract a characteristic seeding curve on the ostium, on which an inflow jet boundary contour is constructed. Based on this boundary contour we identify the impingement zone. Furthermore, we present several visualization techniques to depict both characteristics expressively. Thereby, we consider accuracy and robustness of the extracted characteristics, minimal visual clutter and occlusions. An evaluation with six domain experts confirms that our approach detects both hemodynamic characteristics reasonably.

Does Flexible Arterial Tubing Retain More Hemodynamic Energy During Pediatric Pulsatile Extracorporeal Life Support?

Science.gov (United States)

Wang, Shigang; Kunselman, Allen R; Ündar, Akif

2017-01-01

The objective of this study was to evaluate the hemodynamic performance and energy transmission of flexible arterial tubing as the arterial line in a simulated pediatric pulsatile extracorporeal life support (ECLS) system. The ECLS circuit consisted of a Medos Deltastream DP3 diagonal pump head, Medos Hilite 2400 LT oxygenator, Biomedicus arterial/venous cannula (10 Fr/14 Fr), 3 feet of polyvinyl chloride (PVC) arterial tubing or latex rubber arterial tubing, primed with lactated Ringer's solution and packed red blood cells (hematocrit 40%). Trials were conducted at flow rates of 300 to 1200 mL/min (300 mL/min increments) under nonpulsatile and pulsatile modes at 36°C using either PVC arterial tubing (PVC group) or latex rubber tubing (Latex group). Real-time pressure and flow data were recorded using a custom-based data acquisition system. Mean pressures and energy equivalent pressures (EEP) were the same under nonpulsatile mode between the two groups. Under pulsatile mode, EEPs were significantly great than mean pressure, especially in the Latex group (P tubing retained more hemodynamic energy passing through it under pulsatile mode while mean pressures and pressure drops across the ECLS circuit were similar between PVC and latex rubber arterial tubing. Further studies are warranted to verify our findings. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Cerebral hemodynamic responses to seizure in the mouse brain: simultaneous near-infrared spectroscopy-electroencephalography study

Science.gov (United States)

Lee, Seungduk; Lee, Mina; Koh, Dalkwon; Kim, Beop-Min; Choi, Jee Hyun

2010-05-01

We applied near-infrared spectroscopy (NIRS) and electroencephalography (EEG) simultaneously on the mouse brain and investigated the hemodynamic response to epileptic episodes under pharmacologically driven seizure. γ-butyrolactone (GBL) and 4-aminopyridine (4-AP) were applied to induce absence and tonic-clonic seizures, respectively. The epileptic episodes were identified from the single-channel EEG, and the corresponding hemodynamic changes in different regions of the brain were characterized by multichannel frequency-domain NIRS. Our results are the following: (i) the oxyhemoglobin level increases in the case of GBL-treated mice but not 4-AP-treated mice compared to the predrug state; (ii) the dominant response to each absence seizure is a decrease in deoxyhemolobin; (iii) the phase shift between oxy- and deoxyhemoglobin reduces in GBL-treated mice but no 4-AP-treated mice; and (iv) the spatial correlation of hemodynamics increased significantly in 4-AP-treated mice but not in GBL-treated mice. Our results shows that spatiotemporal tracking of cerebral hemodynamics using NIRS can be successfully applied to the mouse brain in conjunction with electrophysiological recording, which will support the study of molecular, cellular, and network origin of neurovascular coupling in vivo.

Acute effects of chewing tobacco on coronary microcirculation and hemodynamics in habitual tobacco chewers

Directory of Open Access Journals (Sweden)

Vikas Thakran

2015-01-01

Full Text Available Background: Long-term adverse cardiovascular effects of smokeless tobacco are well established, however, the effect of chewing tobacco on coronary microcirculation and hemodynamic have not been studied. We intended to analyze the acute effect of chewing tobacco on coronary microcirculation and hemodynamics in habitual tobacco chewers with stable coronary artery disease undergoing elective percutaneous coronary intervention (PCI. Materials and Methods: We prospectively enrolled seven habitual tobacco chewers with stable coronary artery disease with single vessel disease or double vessel disease satisfying the criteria for elective PCI. Patients were instructed to keep 1 g of crushed dried tobacco leaves in the mouth after a successful PCI. Lesion in last stented vessels was evaluated for fractional flow reserve (FFR, coronary flow reserve (CFR, and index of microcirculatory resistance (IMR post-PCI, after 15 min and 30 min of tobacco chewing along with the measurement of serum cotinine levels. Results: Oral tobacco led to high levels of cotinine in the majority of patients. There was an insignificant rise in heart rate, systolic and diastolic blood pressure following tobacco consumption. Baseline CFR (median 1.6, range 1.1–5.5 was low in tobacco chewers after PCI even after optimum FFR (0.9 ± 0.05 in the majority of patients suggesting abnormal microvascular hemodynamics (high IMR in 3 patients, overall median 14.2, range 7–36.2. However, there was no significant change in the estimated CFR or IMR values following tobacco chewing. One patient had bradycardia and hypotension which may be related to vagal reaction or acute nicotine poisoning. Conclusion: Tobacco chewers have abnormal coronary microcirculation hemodynamics even following a successful PCI. However, the coronary micocirculation and hemodynamics do not change acutely following tobacco chewing despite high serum cotinine concentrations.

Force production during squats performed with a rotational resistance device under stable versus unstable conditions.

Science.gov (United States)

Moras, Gerard; Vázquez-Guerrero, Jairo

2015-11-01

[Purpose] Force production during a squat action on a rotational resistance device (RRD) under stable and unstable conditions. [Subjects and Methods] Twenty-one healthy males were asked to perform six sets of six repetitions of squats on an RRD on either stable or unstable surfaces. The stable and unstable sets were performed on different days. Muscular outputs were obtained from a linear encoder and a strain gauge fixed to a vest. [Results] Overall, the results showed no significant differences for any of the dependent variables across exercise modes. Forcemean outputs were higher in the concentric phase than in the eccentric phase for each condition, but there were no differences in velocity, time or displacement. The forcepeak was similar in the eccentric and concentric phases of movement under both stable and unstable conditions. There were no significant differences in forcemean between sets per condition or between conditions. [Conclusion] These results suggest that performing squats with a RRD achieves similar forcemean and forcepeak under stable and unstable conditions. The forcepeak produced is also similar in concentric and eccentric phases.

Computed Tomography Angiography Evaluation of Risk Factors for Unstable Intracranial Aneurysms.

Science.gov (United States)

Wang, Guang-Xian; Gong, Ming-Fu; Wen, Li; Liu, Lan-Lan; Yin, Jin-Bo; Duan, Chun-Mei; Zhang, Dong

2018-03-19

To evaluate risk factors for instability in intracranial aneurysms (IAs) using computed tomography angiography (CTA). A total of 614 consecutive patients diagnosed with 661 IAs between August 2011 and February 2016 were reviewed. Patients and IAs were divided into stable and unstable groups. Along with clinical characteristics, IA characteristics were evaluated by CTA. Multiple logistic regression analysis was used to identify the independent risk factors associated with unstable IAs. Receiver operating characteristic (ROC) curve analysis was performed on the final model, and optimal thresholds were obtained. Patient age (odds ratio [OR], 0.946), cerebral atherosclerosis (CA; OR, 0.525), and IAs located at the middle cerebral artery (OR, 0.473) or internal carotid artery (OR, 0.512) were negatively correlated with instability, whereas IAs with irregular shape (OR, 2.157), deep depth (OR, 1.557), or large flow angle (FA; OR, 1.015) were more likely to be unstable. ROC analysis revealed threshold values of age, depth, and FA of 59.5 years, 4.25 mm, and 87.8°, respectively. The stability of IAs is significantly affected by several factors, including patient age and the presence of CA. IA shape and location also have an impact on the stability of IAs. Growth into an irregular shape, with a deep depth, and a large FA are risk factors for a change in IAs from stable to unstable. Copyright © 2018 Elsevier Inc. All rights reserved.

Hemodynamic significance of internal carotid artery disease

DEFF Research Database (Denmark)

Schroeder, T

1988-01-01

Neurologic symptoms in the region of an internal carotid artery stenosis are considered to be embolic in most instances. Only in a subgroup has carotid occlusive disease with impairment of the collateral supply, caused a state of hemodynamic failure with marked reduction of perfusion pressure...... stenosis. This is considered a result of chronic low perfusion pressure with subsequent loss of autoregulation, and autoregulatory control is first regained after some days.(ABSTRACT TRUNCATED AT 400 WORDS)...

S3 guidelines for intensive care in cardiac surgery patients: hemodynamic monitoring and cardiocirculary system

Directory of Open Access Journals (Sweden)

Schmitt, D. V.

2010-01-01

Full Text Available Hemodynamic monitoring and adequate volume-therapy, as well as the treatment with positive inotropic drugs and vasopressors are the basic principles of the postoperative intensive care treatment of patient after cardiothoracic surgery. The goal of these S3 guidelines is to evaluate the recommendations in regard to evidence based medicine and to define therapy goals for monitoring and therapy. In context with the clinical situation the evaluation of the different hemodynamic parameters allows the development of a therapeutic concept and the definition of goal criteria to evaluate the effect of treatment. Up to now there are only guidelines for subareas of postoperative treatment of cardiothoracic surgical patients, like the use of a pulmonary artery catheter or the transesophageal echocardiography. The German Society for Thoracic and Cardiovascular Surgery (Deutsche Gesellschaft für Thorax-, Herz- und Gefäßchirurgie, DGTHG and the German Society for Anaesthesiology and Intensive Care Medicine (Deutsche Gesellschaft für Anästhesiologie und lntensivmedizin, DGAI made an approach to ensure and improve the quality of the postoperative intensive care medicine after cardiothoracic surgery by the development of S3 consensus-based treatment guidelines. Goal of this guideline is to assess the available monitoring methods with regard to indication, procedures, predication, limits, contraindications and risks for use. The differentiated therapy of volume-replacement, positive inotropic support and vasoactive drugs, the therapy with vasodilatators, inodilatators and calcium sensitizers and the use of intra-aortic balloon pumps will also be addressed. The guideline has been developed following the recommendations for the development of guidelines by the Association of the Scientific Medical Societies in Germany (AWMF. The presented key messages of the guidelines were approved after two consensus meetings under the moderation of the Association of the

Morphological and Hemodynamic Discriminators for Rupture Status in Posterior Communicating Artery Aneurysms.

Directory of Open Access Journals (Sweden)

Nan Lv

Full Text Available The conflicting findings of previous morphological and hemodynamic studies on intracranial aneurysm rupture may be caused by the relatively small sample sizes and the variation in location of the patient-specific aneurysm models. We aimed to determine the discriminators for aneurysm rupture status by focusing on only posterior communicating artery (PCoA aneurysms.In 129 PCoA aneurysms (85 ruptured, 44 unruptured, clinical, morphological and hemodynamic characteristics were compared between the ruptured and unruptured cases. Multivariate logistic regression analysis was performed to determine the discriminators for rupture status of PCoA aneurysms.While univariate analyses showed that the size of aneurysm dome, aspect ratio (AR, size ratio (SR, dome-to-neck ratio (DN, inflow angle (IA, normalized wall shear stress (NWSS and percentage of low wall shear stress area (LSA were significantly associated with PCoA aneurysm rupture status. With multivariate analyses, significance was only retained for higher IA (OR = 1.539, p < 0.001 and LSA (OR = 1.393, p = 0.041.Hemodynamics and morphology were related to rupture status of intracranial aneurysms. Higher IA and LSA were identified as discriminators for rupture status of PCoA aneurysms.

Hemodynamic changes in rats after radioprotective combination of cystamine administered subcutaneously and 5-methoxytryptamine injected intramuscularly

International Nuclear Information System (INIS)

Kuna, P.

1976-01-01

Administration of cystamine (20 mg base/kg s.c.) and 5-methoxytryptamine (10 mg base/kg i.m.) with 12 minutes delay to anesthetized rats induced the depression of whole cardiovascular system, hemoconcentration and great blood flow decrease in the radiosensitive tissues. Distribution of lowered cardiac output preferred the fractions to brain, heart, liver and lungs. Hemodynamic responses to protective combination may participate in its radioprotective action. (orig.) [de

Stable and unstable crack growth in Type 304 stainless steel plate

International Nuclear Information System (INIS)

Yagawa, G.

1984-01-01

Experimental and theoretical results on stable as well as unstable fractures for Type 304 stainless steel plates with a central crack subjected to tension force are given. In the experiment using a testing machine with a special spring for high compliance, the transition points from the stable to the unstable crack growth are observed and comparisons are made between the test results and the finite element solutions. A round robin calculation for the elastic-plastic stable crack growth using one of the specimens mentioned above is also given. (orig.)

Unstable angina pectoris: the results of intracoronary administration of fibrinolytic agents

International Nuclear Information System (INIS)

Gratsianskij, N.A.; Panchenko, E.P.; Agapov, A.A.; Logutov, Yu.A.; Vladimirov, S.S.

1986-01-01

Intracoronary thrombolytic infusions were used in 10 patients with unstable angina and high risk of myocardial infarction (MI). Streptokinase (500.000 units per hour) was used in 9 patients, and urokinase, in one. Vascular recanalization was achieved in 4 cases where angiografhy, showed coronary arterial occlusion by a thrombus. Myocardial infarction developed in 8 patients (large-focal in 6 and small focal in 2) within 1 to 16 days after the thrombolytic infuson. Therefore, short-term local thrombolytic infusion fails to prevent myocardial infarction in patients with unstable angina

Boundary Between Stable and Unstable Regimes of Accretion

Directory of Open Access Journals (Sweden)

Blinova A. A.

2014-01-01

Full Text Available We investigated the boundary between stable and unstable regimes of accretion and its dependence on different parameters. Simulations were performed using a “cubed sphere" code with high grid resolution (244 grid points in the azimuthal direction, which is twice as high as that used in our earlier studies. We chose a very low viscosity value, with alpha-parameter α=0.02. We observed from the simulations that the boundary strongly depends on the ratio between magnetospheric radius rm (where the magnetic stress in the magnetosphere matches the matter stress in the disk and corotation radius rcor (where the Keplerian velocity in the disk is equal to the angular velocity of the star. For a small misalignment angle of the dipole field, Θ = 5°, accretion is unstable if rcor/rm> 1.35, and is stable otherwise. In cases of a larger misalignment angle of the dipole, Θ = 20°, instability occurs at slightly larger values, rcor/rm> 1.41

Hemodynamic measurement using four-dimensional phase-contrast MRI: Quantification of hemodynamic parameters and clinical applications

Energy Technology Data Exchange (ETDEWEB)

Ha, Ho Jin; Lee, Sang Joon [POSTECH Biotech Center, Pohang University of Science and Technology, Pohang (Korea, Republic of); Kim, Guk Bae; Kweon, Ji Hoon; Kim, Young Hak; Lee, Deok Hee; Yang, Dong Hyun; KIm, Nam Kug [Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of)

2016-07-15

Recent improvements have been made to the use of time-resolved, three-dimensional phase-contrast (PC) magnetic resonance imaging (MRI), which is also named four-dimensional (4D) PC-MRI or 4D flow MRI, in the investigation of spatial and temporal variations in hemodynamic features in cardiovascular blood flow. The present article reviews the principle and analytical procedures of 4D PC-MRI. Various fluid dynamic biomarkers for possible clinical usage are also described, including wall shear stress, turbulent kinetic energy, and relative pressure. Lastly, this article provides an overview of the clinical applications of 4D PC-MRI in various cardiovascular regions.

Hemodynamic Measurement Using Four-Dimensional Phase-Contrast MRI: Quantification of Hemodynamic Parameters and Clinical Applications

Energy Technology Data Exchange (ETDEWEB)

Ha, Hojin [POSTECH Biotech Center, Pohang University of Science and Technology, Pohang 37673 (Korea, Republic of); Kim, Guk Bae [Asan Institute of Life Science, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505 (Korea, Republic of); Kweon, Jihoon [Department of Cardiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505 (Korea, Republic of); Lee, Sang Joon [POSTECH Biotech Center, Pohang University of Science and Technology, Pohang 37673 (Korea, Republic of); Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang 37673 (Korea, Republic of); Kim, Young-Hak [Department of Cardiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505 (Korea, Republic of); Lee, Deok Hee; Yang, Dong Hyun [Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505 (Korea, Republic of); Kim, Namkug [Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505 (Korea, Republic of); Department of Convergence Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505 (Korea, Republic of)

2016-11-01

Recent improvements have been made to the use of time-resolved, three-dimensional phase-contrast (PC) magnetic resonance imaging (MRI), which is also named four-dimensional (4D) PC-MRI or 4D flow MRI, in the investigation of spatial and temporal variations in hemodynamic features in cardiovascular blood flow. The present article reviews the principle and analytical procedures of 4D PC-MRI. Various fluid dynamic biomarkers for possible clinical usage are also described, including wall shear stress, turbulent kinetic energy, and relative pressure. Lastly, this article provides an overview of the clinical applications of 4D PC-MRI in various cardiovascular regions.

A new CT-score as index of hemodynamic changes in patients with chronic thromboembolic pulmonary hypertension.

Science.gov (United States)

Leone, Maria Barbara; Giannotta, Marica; Palazzini, Massimiliano; Cefarelli, Mariano; Martìn Suàrez, Sofia; Gotti, Enrico; Bacchi Reggiani, Maria Letizia; Zompatori, Maurizio; Galiè, Nazzareno

2017-07-01

The aim of this study was to retrospectively assess the relationship between radiological and hemodynamic parameters in patients with chronic thromboembolic pulmonary hypertension (CTEPH). We introduced a new CT-score to evaluate hemodynamic changes, only employing CT-pulmonary angiography (CTPA). 145 patients affected by CTEPH underwent hemodynamic and CTPA evaluation. Among these 145 patients, 69 underwent pulmonary endarterectomy (PEA) and performed a CTPA evaluation even after surgery. Hemodynamic assessment considered the values of mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR), obtained through right heart catheterization (RHC). Radiological evaluation included CTPA signs of pulmonary hypertension. A highly significant statistical correlation was observed between the new CT-score and both mPAP and PVR (p < 0.000) in the whole sample and also in the subgroup who underwent PEA. In addition, mPAP and PVR showed an important association with the severity of mosaic perfusion (p < 0.000). mPAP also correlated with main pulmonary artery diameter (p < 0.01); a significant association was found in both between PVR and tricuspid regurgitation(p < 0.000) and with PVR and presence of unilateral or bilateral pulmonary thromboembolic occlusion (p < 0.05). Our results confirm the diagnostic role of CTPA in evaluating patients with CTEPH and in addition open a new horizon in assessing hemodynamic changes in patients with CTEPH, only employing a CTPA, especially when RHC is contraindicated or not possible.

Influence of unstable footwear on lower leg muscle activity, volume change and subjective discomfort during prolonged standing.

Science.gov (United States)

Karimi, Zanyar; Allahyari, Teimour; Azghani, Mahmood Reza; Khalkhali, Hamidreza

2016-03-01

The present study was an attempt to investigate the effect of unstable footwear on lower leg muscle activity, volume change and subjective discomfort during prolonged standing. Ten healthy subjects were recruited to stand for 2 h in three footwear conditions: barefoot, flat-bottomed shoe and unstable shoe. During standing, lower leg discomfort and EMG activity of medial gastrocnemius (MG) and tibialis anterior (TA) muscles were continuously monitored. Changes in lower leg volume over standing time also were measured. Lower leg discomfort rating reduced significantly while subjects standing on unstable shoe compared to the flat-bottomed shoe and barefoot condition. For lower leg volume, less changes also were observed with unstable shoe. The activity level and variation of right MG muscle was greater with unstable shoe compared to the other footwear conditions; however regarding the left MG muscle, significant difference was found between unstable shoe and flat-bottomed shoe only for activity level. Furthermore no significant differences were observed for the activity level and variation of TA muscles (right/left) among all footwear conditions. The findings suggested that prolonged standing with unstable footwear produces changes in lower leg muscles activity and leads to less volume changes. Perceived discomfort also was lower for this type of footwear and this might mean that unstable footwear can be used as ergonomic solution for employees whose work requires prolonged standing. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Computational modeling of local hemodynamics phenomena: methods, tools and clinical applications

International Nuclear Information System (INIS)

Ponzini, R.; Rizzo, G.; Vergara, C.; Veneziani, A.; Morbiducci, U.; Montevecchi, F.M.; Redaelli, A.

2009-01-01

Local hemodynamics plays a key role in the onset of vessel wall pathophysiology, with peculiar blood flow structures (i.e. spatial velocity profiles, vortices, re-circulating zones, helical patterns and so on) characterizing the behavior of specific vascular districts. Thanks to the evolving technologies on computer sciences, mathematical modeling and hardware performances, the study of local hemodynamics can today afford also the use of a virtual environment to perform hypothesis testing, product development, protocol design and methods validation that just a couple of decades ago would have not been thinkable. Computational fluid dynamics (Cfd) appears to be more than a complementary partner to in vitro modeling and a possible substitute to animal models, furnishing a privileged environment for cheap fast and reproducible data generation.

A high-power diode-laser-pumped CW Nd:YAG laser using a stable-unstable resonator

International Nuclear Information System (INIS)

Mudge, M.; Ostermeyer, P.; Veitch, J.; Munch, J.; Hamilton, M.W.

2000-01-01

Full text: The design and operation of a power-scalable diode-laser-pumped CW Nd:YAG zigzag slab laser that uses a stable-unstable resonator with a graded reflectivity mirror as an output coupler is described. We demonstrate control of the thermal lens strength in the unstable plane and weak thermal lensing in the stable plane that is independent of pump power, vital for efficient scalability. This enabled CW operation of the stable-unstable resonator with excellent near- and far-field beam quality

Challenges in modeling unstable two-phase flow experiments in porous micromodels

Science.gov (United States)

Meheust, Y.; Ferrari, A.; Jimenez-Martinez, J.; Le Borgne, T.; Lunati, I.

2014-12-01

The simulation of unstable invasion patterns in porous media flow is challenging since small perturbations tend to grow in time, so that slight differences in geometry or initial conditions potentially give rise to significantly different solutions. Here we present a detailed comparison of pore scale simulations and experiments of unstable primary drainage in porous micromodels. The porous medium consists of a Hele-Shaw cell containing cylindrical obstacles. Two experimental flow cells have been constructed by soft lithography, with different degrees of heterogeneity in the grain size distribution. To model two-phase flow at the pore scale, we solve Navier-Stokes equations for mass and momentum conservation in the discretized pore space and employ the Volume of Fluid (VOF) method to track the evolution of the interface. During drainage, if the defending fluid is the most viscous, viscous forces destabilize the interface, giving rise to the formation of preferential flow paths, in the form of a branched fingering structure. We test different numerical models (a 2D vertical integrated model and a full 3D model) and different initial conditions, studying their impact on the simulated spatial distributions of the fluid phases. Although due to the unstable nature of the invasion, small discrepancies between the experimental setup and the numerical model can result in different fluids patterns (see figure), simulations show a satisfactory agreement with the structures observed experimentally. To estimate the ability of the numerical approach to reproduce unstable displacement, we compare several quantities in both the statistical and deterministic sense. We demonstrate the impact of three main sources of uncertainty : i) the uncertainty on the pore space geometry, ii) the interface initialization and ii) three dimensional effects [1]. Simulations in weakly heterogeneous geometries are found to be more challenging because uncertainties on pore neck widths are on the same

Small Kerr-anti-de Sitter black holes are unstable

International Nuclear Information System (INIS)

Cardoso, Vitor; Dias, Oscar J.C.

2004-01-01

Superradiance in black hole spacetimes can trigger instabilities. Here we show that, due to superradiance, small Kerr-anti-de Sitter black holes are unstable. Our demonstration uses a matching procedure, in a long wavelength approximation

Time-dependent 3D simulations of the hemodynamics in a stented coronary artery

International Nuclear Information System (INIS)

Faik, Isam; Mongrain, Rosaire; Leask, Richard L; Rodes-Cabau, Josep; Larose, Eric; Bertrand, Olivier

2007-01-01

Stenting is becoming the major interventional cardiology procedure worldwide. However restenosis remains a major limitation to the effectiveness of stents. Alterations to the local hemodynamics in the stented segment of the artery could be a potential factor in the development of in-stent restenosis. The characterization of wall shear stress and of blood flow patterns in a stented artery is therefore necessary for a good understanding of the role of hemodynamics in the development of in-stent restenosis. We have used a time-dependent 3D numerical model of a stented coronary artery to study the characteristics of the blood flow and the shear stress distribution. Our results show that the presence of the stent produces significant secondary flow that is limited to an annulus in the near wall region. Low shear stress zones were localized in the vicinity of the struts while the tips of the struts exhibited high values of shear stress. These results support the hypothesis that local hemodynamics may affect the development of in-stent restenosis and could influence the choice of stent geometries for future stent designs

Dietary melatonin alters uterine artery hemodynamics in pregnant holstein heifers

Science.gov (United States)

The objective was to examine uterine artery hemodynamics and maternal serum profiles in pregnant heifers supplemented with dietary melatonin (MEL) or no supplementation (CON). In addition, melatonin receptor–mediated responses in steroid metabolism were examined using a bovine endometrial epithelial...

The effect of dim light at night on cerebral hemodynamic oscillations during sleep: A near-infrared spectroscopy study.

Science.gov (United States)

Kim, Tae-Joon; Lee, Byeong Uk; Sunwoo, Jun-Sang; Byun, Jung-Ick; Moon, Jangsup; Lee, Soon-Tae; Jung, Keun-Hwa; Chu, Kon; Kim, Manho; Lim, Jong-Min; Lee, Eunil; Lee, Sang Kun; Jung, Ki-Young

2017-01-01

Recent studies have reported that dim light at night (dLAN) is associated with risks of cardiovascular complications, such as hypertension and carotid atherosclerosis; however, little is known about the underlying mechanism. Here, we evaluated the effect of dLAN on the cerebrovascular system by analyzing cerebral hemodynamic oscillations using near-infrared spectroscopy (NIRS). Fourteen healthy male subjects underwent polysomnography coupled with cerebral NIRS. The data collected during sleep with dim light (10 lux) were compared with those collected during sleep under the control dark conditions for the sleep structure, cerebral hemodynamic oscillations, heart rate variability (HRV), and their electroencephalographic (EEG) power spectrum. Power spectral analysis was applied to oxy-hemoglobin concentrations calculated from the NIRS signal. Spectral densities over endothelial very-low-frequency oscillations (VLFOs) (0.003-0.02 Hz), neurogenic VLFOs (0.02-0.04 Hz), myogenic low-frequency oscillations (LFOs) (0.04-0.15 Hz), and total LFOs (0.003-0.15 Hz) were obtained for each sleep stage. The polysomnographic data revealed an increase in the N2 stage under the dLAN conditions. The spectral analysis of cerebral hemodynamics showed that the total LFOs increased significantly during slow-wave sleep (SWS) and decreased during rapid eye movement (REM) sleep. Specifically, endothelial (median of normalized value, 0.46 vs. 0.72, p = 0.019) and neurogenic (median, 0.58 vs. 0.84, p = 0.019) VLFOs were enhanced during SWS, whereas endothelial VLFOs (median, 1.93 vs. 1.47, p = 0.030) were attenuated during REM sleep. HRV analysis exhibited altered spectral densities during SWS induced by dLAN, including an increase in very-low-frequency and decreases in low-frequency and high-frequency ranges. In the EEG power spectral analysis, no significant difference was detected between the control and dLAN conditions. In conclusion, dLAN can disturb cerebral hemodynamics via the

Glasgow Coma Scores, Early Opioids, and Posttraumatic Stress Disorder Among Combat Amputees

Science.gov (United States)

2014-04-01

extracted from in- theater patient encounter forms by Expeditionary Medical En- counter Database trauma nurses . GCS scores of 3 to 12 in- dicate moderate to...that may negatively impact hemodynamics (Fox et al., 1995). Combat-trauma anes- thesiologists are advised to minimize these side effects when managing...the most seriously injured and/or hemodynamically unstable patients. The present findings are consistent with this principle of combat casualty care by

Effects of dipyridamole and aminophylline on hemodynamics, regional myocardial blood flow and thallium-201 washout in the setting of a critical coronary stenosis

International Nuclear Information System (INIS)

Granato, J.E.; Watson, D.D.; Belardinelli, L.; Cannon, J.M.; Beller, G.A.

1990-01-01

Experiments were performed to characterize the interaction of intravenous dipyridamole and aminophylline on thallium-201 transport kinetics, regional myocardial blood flow and systemic hemodynamics in the presence of a critical coronary artery stenosis. In 12 dogs with a critical left anterior descending coronary artery stenosis, arterial pressure decreased from a mean value (+/- SEM) of 107 +/- 6 to 94 +/- 3 mm Hg and distal left anterior descending artery pressure decreased from 70 +/- 7 to 55 +/- 4 mm Hg after intravenous administration of dipyridamole. In the left anterior descending perfusion zone, the endocardial/epicardial flow ratio decreased from 0.70 to 0.36 and the intrinsic thallium washout rate was significantly prolonged. Intravenous aminophylline reversed the dipyridamole-induced systemic hypotension and transmural coronary steal and restored the thallium washout rate to baseline values. In six other dogs, aminophylline alone resulted in no alterations in systemic and coronary hemodynamics or regional myocardial blood flow. As expected, dipyridamole-induced vasodilation and coronary steal were prevented by aminophylline pretreatment. These data show that in a canine model of partial coronary stenosis, systemic hypotension, adverse regional flow effects and prolonged thallium-201 washout consequent to intravenously administered dipyridamole are promptly reversed by intravenous aminophylline administration. Aminophylline alone had no significant hemodynamic and coronary flow effects. This study provides further insight into the altered thallium kinetics occurring as a consequence of dipyridamole-induced vasodilation and suggests that the prompt reversal of symptoms and signs of ischemia with aminophylline in patients receiving intravenous dipyridamole for clinical imaging studies probably reflects the reversal of transmural coronary steal

The Adverse Events and Hemodynamic Effects of Adenosine-Based Cardiac MRI

International Nuclear Information System (INIS)

Voigtlander, Thomas; Magedanz, Annett; Schmermund, Axel; Bramlage, Peter; Elsaesser, Amelie; Kauczor, Hans-Ulrich; Mohrs, Oliver K.

2011-01-01

We wanted to prospectively assess the adverse events and hemodynamic effects associated with an intravenous adenosine infusion in patients with suspected or known coronary artery disease and who were undergoing cardiac MRI. One hundred and sixty-eight patients (64 ± 9 years) received adenosine (140 μg/kg/min) during cardiac MRI. Before and during the administration, the heart rate, systemic blood pressure, and oxygen saturation were monitored using a MRI-compatible system. We documented any signs and symptoms of potential adverse events. In total, 47 out of 168 patients (28%) experienced adverse effects, which were mostly mild or moderate. In 13 patients (8%), the adenosine infusion was discontinued due to intolerable dyspnea or chest pain. No high grade atrioventricular block, bronchospasm or other life-threatening adverse events occurred. The hemodynamic measurements showed a significant increase in the heart rate during adenosine infusion (69.3 ± 11.7 versus 82.4 ± 13.0 beats/min, respectively; p < 0.001). A significant but clinically irrelevant increase in oxygen saturation occurred during adenosine infusion (96 ± 1.9% versus 97 ± 1.3%, respectively; p < 0.001). The blood pressure did not significantly change during adenosine infusion (systolic: 142.8 ± 24.0 versus 140.9 ± 25.7 mmHg; diastolic: 80.2 ± 12.5 mmHg versus 78.9 ± 15.6, respectively). This study confirms the safety of adenosine infusion during cardiac MRI. A considerable proportion of all patients will experience minor adverse effects and some patients will not tolerate adenosine infusion. However, all adverse events can be successfully managed by a radiologist. The increased heart rate during adenosine infusion highlights the need to individually adjust the settings according to the patient, e.g., the number of slices of myocardial perfusion imaging.

Effects of a human recombinant alkaline phosphatase on renal hemodynamics, oxygenation and inflammation in two models of acute kidney injury

Energy Technology Data Exchange (ETDEWEB)

Peters, Esther, E-mail: esther.peters@radboudumc.nl [Department of Intensive Care Medicine, Radboud university medical center, PO Box 9101, Internal Mailbox 710, 6500 HB, Nijmegen (Netherlands); Department of Pharmacology and Toxicology, Radboud university medical center, PO Box 9101, Internal Mailbox 149, 6500 HB, Nijmegen (Netherlands); Ergin, Bülent, E-mail: b.ergin@amc.uva.nl [Department of Translational Physiology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam (Netherlands); Kandil, Asli, E-mail: aslikandil@istanbul.edu.tr [Department of Biology, Faculty of Science, Istanbul University, PK 34134, Vezneciler, Istanbul (Turkey); Gurel-Gurevin, Ebru, E-mail: egurelgurevin@gmail.com [Department of Biology, Faculty of Science, Istanbul University, PK 34134, Vezneciler, Istanbul (Turkey); Elsas, Andrea van, E-mail: a.vanelsas@am-pharma.com [AM-Pharma, Rumpsterweg 6, 3981 AK, Bunnik (Netherlands); Masereeuw, Rosalinde, E-mail: r.masereeuw@uu.nl [Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, PO Box 80082, 3508 TB Utrecht (Netherlands); Pickkers, Peter, E-mail: peter.pickkers@radboudumc.nl [Department of Intensive Care Medicine, Radboud university medical center, PO Box 9101, Internal Mailbox 710, 6500 HB, Nijmegen (Netherlands); Ince, Can, E-mail: c.ince@amc.uva.nl [Department of Translational Physiology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam (Netherlands)

2016-12-15

Two small clinical trials indicated that administration of bovine intestinal alkaline phosphatase (AP) improves renal function in critically ill patients with sepsis-associated acute kidney injury (AKI), for which the mechanism of action is not completely understood. Here, we investigated the effects of a newly developed human recombinant AP (recAP) on renal oxygenation and hemodynamics and prevention of kidney damage and inflammation in two in vivo AKI models. To induce AKI, male Wistar rats (n = 18) were subjected to renal ischemia (30 min) and reperfusion (I/R), or sham-operated. In a second model, rats (n = 18) received a 30 min infusion of lipopolysaccharide (LPS; 2.5 mg/kg), or saline, and fluid resuscitation. In both models, recAP (1000 U/kg) was administered intravenously (15 min before reperfusion, or 90 min after LPS). Following recAP treatment, I/R-induced changes in renal blood flow, renal vascular resistance and oxygen delivery at early, and cortical microvascular oxygen tension at late reperfusion were no longer significantly affected. RecAP did not influence I/R-induced effects on mean arterial pressure. During endotoxemia, recAP treatment did not modulate the LPS-induced changes in systemic hemodynamics and renal oxygenation. In both models, recAP did exert a clear renal protective anti-inflammatory effect, demonstrated by attenuated immunostaining of inflammatory, tubular injury and pro-apoptosis markers. Whether this renal protective effect is sufficient to improve outcome of patients suffering from sepsis-associated AKI is being investigated in a large clinical trial. - Highlights: • Human recombinant alkaline phosphatase (recAP) is a potential new therapy for sepsis-associated acute kidney injury (AKI). • RecAP can modulate renal oxygenation and hemodynamics immediately following I/R-induced AKI. • RecAP did not modulate endotoxemia-induced changes in systemic hemodynamics and renal oxygenation. • RecAP did exert a clear renal protective

Damping capacity of unstable steels on chromium-nickel-manganese base

Energy Technology Data Exchange (ETDEWEB)

Kochkin, L.I.; Rudakov, A.A. (Kirovskij Politekhnicheskij Inst. (USSR))

1982-02-01

The paper deals with results of a study on the energy scattering in OKh13N3G8, 20Kh13N3G4 and 30Kh13N3G4 unstable steels. It is shown that the development of microplastic strains most easily occurs in low-carbon steel having a two-phase structure in the initial state. The proceeding of microplastic deformations in carbon unstable steels is limited by the interstitial atom effect on the dislocation movement. It is established that in OKh13N3G8 steel the martensite ..cap alpha --> gamma..- transformation begins under the cyclic stress amplitudes below the yield point of this steel. The steels studied possess a high vibrostrength.

Stable or unstable tear of the anterior cruciate ligament of the knee: an MR diagnosis?

Energy Technology Data Exchange (ETDEWEB)

Dyck, Pieter van; Gielen, Jan L.; Parizel, Paul M. [University Hospital Antwerp and University of Antwerp, Department of Radiology, Edegem (Belgium); Vanhoenacker, Filip M. [University Hospital Antwerp and University of Antwerp, Department of Radiology, Edegem (Belgium); AZ St-Maarten Duffel/Mechelen, Department of Radiology, Duffel (Belgium); Wouters, Kristien [University Hospital Antwerp and University of Antwerp, Department of Scientific Coordination and Biostatistics, Edegem (Belgium); Dossche, Lieven [University Hospital Antwerp and University of Antwerp, Department of Orthopedics, Edegem (Belgium)

2012-03-15

To determine the usefulness of magnetic resonance (MR) imaging to distinguish stable from unstable tears of the anterior cruciate ligament (ACL) of the knee. MR images of 97 patients with surgically confirmed ACL tear were retrospectively reviewed. According to arthroscopic and clinical examination, these patients had 36 stable and 61 unstable (9 partial and 52 complete) ACL tears. MR images were interpreted by two blinded reviewers and scored with respect to previously reported primary and secondary MR signs of ACL injury. Based on a comprehensive assessment of all the MR findings, ACLs were categorized as being stable or unstable. MR accuracy was calculated considering only primary MR signs and considering both primary and secondary MR signs of ACL injury, separately. Accuracy of each individual primary and secondary MR sign was calculated. Considering only primary MR signs, sensitivity, specificity, and accuracy of MR were 77, 92, and 82%, respectively. Considering both primary and secondary MR signs, sensitivity, specificity, and accuracy of MR were 59, 81, and 67%, respectively. Of all MR signs, discontinuity and abnormal orientation had highest test accuracy (79 and 87%, respectively). Anterior tibial translation, uncovering of the posterior horn of the lateral meniscus, and hyperbuckled PCL were only seen in unstable ACLs (specificity 100%), but these secondary findings had low sensitivity (23%). Bone contusion around the lateral knee compartment was seen in both unstable and stable ACLs (accuracy 64%). Previously reported MR imaging signs do not allow accurate distinction between clinically stable and unstable ACL injuries. Anterior tibial translation, uncovering of the posterior horn of the lateral meniscus, and hyperbuckled PCL, if present, are helpful signs in the diagnosis of an unstable tear. The presence of bone marrow edema around the lateral knee compartment is not predictive of ACL insufficiency. (orig.)

Effects of an interatrial shunt on rest and exercise hemodynamics

DEFF Research Database (Denmark)

Kaye, David; Shah, Sanjiv J; Borlaug, Barry A

2014-01-01

BACKGROUND: A treatment based on an interatrial shunt device has been proposed for counteracting elevated pulmonary capillary wedge pressure (PCWP) in patients with heart failure and mildly reduced or preserved ejection fraction (HFpEF). We tested the theoretical hemodynamic effects of this appro...

Long-term effects of electrical neurostimulation in patients with unstable angina : Refractory to conventional therapies

NARCIS (Netherlands)

de Vries, Jessica; DeJongste, Mike J. L.; Zijlstra, Felix; Staal, Michiel

2007-01-01

Background. Patients with unstable angina pectoris may become refractory to conventional therapies. Electrical neurostimulation with transcutaneous electrical stimulation and/or spinal cord stimulation has been shown to be effective for patients with refractory unstable angina pectoris in hospital

Hemodynamic and neuroendocrine responses to changes in sodium intake in compensated heart failure

DEFF Research Database (Denmark)

Damgaard, Morten; Norsk, Peter; Gustafsson, Finn

2005-01-01

inhibitors and beta-adrenoreceptor blockers. Therefore, we determined the hemodynamic and neuroendocrine responses to 1 wk of a low-sodium diet (70 mmol/day) and 1 wk of a high-sodium diet (250 mmol/day) in 12 HF patients and 12 age-matched controls in a randomized, balanced fashion. During steady......-state conditions, hemodynamic and neuroendocrine examinations were performed at rest and during bicycle exercise. In seated HF patients, high sodium intake increased body weight (1.6 +/- 0.4%), plasma volume (9 +/- 2%), cardiac index (14 +/- 6%), and stroke volume index (21 +/- 5%), whereas mean arterial pressure...