Time sequential prediction of ventricular-vascular interactions

1986 ◽  
Vol 251 (6) ◽  
pp. H1341-H1353 ◽  
Author(s):  
T. W. Latson ◽  
W. C. Hunter ◽  
D. Burkhoff ◽  
K. Sagawa
Keyword(s):  
Peak Pressure ◽  
Peak Flow ◽  
Impulse Response Function ◽  
Internal Resistance ◽  
Arterial System ◽  
Analytical Technique ◽  
Sequential Prediction ◽  
Loading Effects ◽  
Instantaneous Pressure

A new analytical method (sequential convolution) for describing ventricular-vascular interactions was used to predict instantaneous pressure and flow in four isolated canine left ventricles ejecting into a computer-simulated arterial system. Ventricular pumping ability was described by a load-independent elastance, [E*(t)] combined with a ventricular internal resistance. “Arterial” properties were characterized using a time-based impulse response function that is derived from impedance measurements. Sequential convolution was then used to couple these independent descriptions of ventricular and vascular properties. Predicted pressure-volume trajectories, as well as instantaneous pressures and flows, closely matched the experimental data. Stroke volume, peak pressure, and peak flow were typically within 5% of measured values. This method provides a powerful analytical technique for examining ventricular-vascular interactions and has potential application in evaluating the ventricular-loading effects of more complex in vivo vascular properties.

Vascular peripheral resistance and compliance in the lobster Homarus americanus

1997 ◽  
Vol 200 (3) ◽  
pp. 477-485 ◽  
Author(s):  
J Wilkens ◽  
G Davidson ◽  
M Cavey
Keyword(s):  
Striated Muscle ◽  
Peripheral Resistance ◽  
Systolic Pressure ◽  
Body Part ◽  
Homarus Americanus ◽  
Arterial System ◽  
Flow Rates ◽  
Flow Through ◽  
Lateral Walls

The peripheral resistance to flow through each arterial bed (in actuality, the entire pathway from the heart back to the pericardial sinus) and the mechanical properties of the seven arteries leaving the lobster heart are measured and compared. Resistance is inversely proportional to artery radius and, for each pathway, the resistance falls non-linearly as flow rate increases. The resistance of the hepatic arterial system is lower than that predicted on the basis of its radius. Body-part posture and movement may affect the resistance to perfusion of that region. The total vascular resistance placed on the heart when each artery is perfused at a rate typical of in vivo flow rates is approximately 1.93 kPa s ml-1. All vessels exhibit adluminal layers of fibrils and are relatively compliant at pressures at or below heart systolic pressure. Arteries become stiffer at pressures greater than peak systolic pressure and at radii greater than twice the unpressurized radius. The dorsal abdominal artery possesses striated muscle in the lateral walls. This artery remains compliant over the entire range of hemolymph pressures expected in lobsters. These trends are illustrated when the incremental modulus of elasticity is compared among arteries. All arteries should function as Windkessels to damp the pulsatile pressures and flows generated by the heart. The dorsal abdominal artery may also actively regulate its flow.

scholarly journals The effect of focus size and intensity on stone fragmentation in SWL on a piezoelectric lithotripter

2020 ◽  
Vol 38 (10) ◽  
pp. 2645-2650
Author(s):  
Julian Veser ◽  
Victoria Jahrreiss ◽  
Christian Seitz ◽  
Mehmet Özsoy
Keyword(s):  
Shock Wave Lithotripsy ◽  
Statistical Difference ◽  
Peak Pressure ◽  
Median Number ◽  
Output Pressure ◽  
Multiple Parameters ◽  
Stone Fragmentation ◽  
Stone Migration ◽  
Mesh Cage

Abstract Purpose We aim to analyze the efficacy of different focus sizes and the influence of pulse pressure (intensity) during shock wave lithotripsy (SWL) in terms of stone fragmentation. Methods Combination of three focal sizes (F1 = 2 mm, F2 = 4 mm, F3 = 8 mm) and 11 output pressure settings (intensity 10–20) of a piezoelectric lithotripter (Wolf PiezoLith 3000) were tested on artificial stones (n = 99). The stones were placed within a 2 mm mesh cage. The needed number of shockwaves (SW) to first visible crack, 50% and 100% stone disintegration were recorded. Results Similar number of SW’s were observed until the first crack 10, 11 and 11 SW’s for F1, F2, and F3, respectively (p > 0,05). The median number of SW needed for 50% stone disintegration was 245 for F1 group, 242 for F2 group and 656 for F3 group. F1 vs F2 p = 0.7, F1 vs F3 and F2 vs F3 p < 0.05. Similarly, with larger focus size a higher number of shockwaves were necessary for 100% stone disintegration. 894, 877 and 1708 SW’s for F1, F2 and F3, respectively. Only for F1 vs F3 and F2 vs F3 (all p < 0.05) a statistical difference was observed. These findings were consistent in all different power settings, with an increased difference in lower power levels (≤ 14). Conclusions A smaller focus size, as well as a higher peak pressure results in a more effective stone fragmentation. However, these results need to be confirmed in an in vivo setting with multiple parameters interfering the efficacy, like BMI, respiration or stone migration.

scholarly journals The immunoregulation of mesenchymal stem cells plays a critical role in improving the prognosis of liver transplantation

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Chenxia Hu ◽  
Lanjuan Li
Keyword(s):  
Liver Transplantation ◽  
Natural Killer ◽  
Immune Cells ◽  
Adaptive Systems ◽  
Critical Role ◽  
Arterial System ◽  
Cell Mediated Immunity ◽  
Adaptive Immune Cells

AbstractThe liver is supplied by a dual blood supply, including the portal venous system and the hepatic arterial system; thus, the liver organ is exposed to multiple gut microbial products, metabolic products, and toxins; is sensitive to extraneous pathogens; and can develop liver failure, liver cirrhosis and hepatocellular carcinoma (HCC) after short-term or long-term injury. Although liver transplantation (LT) serves as the only effective treatment for patients with end-stage liver diseases, it is not very popular because of the complications and low survival rates. Although the liver is generally termed an immune and tolerogenic organ with adaptive systems consisting of humoral immunity and cell-mediated immunity, a high rejection rate is still the main complication in patients with LT. Growing evidence has shown that mesenchymal stromal cell (MSC) transplantation could serve as an effective immunomodulatory strategy to induce tolerance in various immune-related disorders. MSCs are reported to inhibit the immune response from innate immune cells, including macrophages, dendritic cells (DCs), natural killer cells (NK cells), and natural killer T (NKT) cells, and that from adaptive immune cells, including T cells, B cells and other liver-specific immune cells, for the generation of a tolerogenic microenvironment. In this review, we summarized the relationship between LT and immunoregulation, and we focused on how to improve the effects of MSC transplantation to improve the prognosis of LT. Only after exhaustive clarification of the potential immunoregulatory mechanisms of MSCs in vitro and in vivo can we implement MSC protocols in routine clinical practice to improve LT outcome.

scholarly journals Ratiometric analysis using Raman spectroscopy as a powerful predictor of structural properties of fatty acids

2018 ◽  
Vol 5 (12) ◽  
pp. 181483 ◽  
Author(s):  
Lauren E. Jamieson ◽  
Angela Li ◽  
Karen Faulds ◽  
Duncan Graham
Keyword(s):  
Fatty Acids ◽  
Raman Spectroscopy ◽  
Biological Sample ◽  
Ex Vivo ◽  
Degree Of Saturation ◽  
Specific Information ◽  
Analytical Technique ◽  
Starting Point

Raman spectroscopy has been used extensively for the analysis of biological samples in vitro , ex vivo and in vivo . While important progress has been made towards using this analytical technique in clinical applications, there is a limit to how much chemically specific information can be extracted from a spectrum of a biological sample, which consists of multiple overlapping peaks from a large number of species in any particular sample. In an attempt to elucidate more specific information regarding individual biochemical species, as opposed to very broad assignments by species class, we propose a bottom-up approach beginning with a detailed analysis of pure biochemical components. Here, we demonstrate a simple ratiometric approach applied to fatty acids, a subsection of the lipid class, to allow the key structural features, in particular degree of saturation and chain length, to be predicted. This is proposed as a starting point for allowing more chemically and species-specific information to be elucidated from the highly multiplexed spectrum of multiple overlapping signals found in a real biological sample. The power of simple ratiometric analysis is also demonstrated by comparing the prediction of degree of unsaturation in food oil samples using ratiometric and multivariate analysis techniques which could be used for food oil authentication.

Estimation of total arterial compliance: an improved method and evaluation of current methods

1986 ◽  
Vol 251 (3) ◽  
pp. H588-H600 ◽  
Author(s):  
Z. Liu ◽  
K. P. Brin ◽  
F. C. Yin
Keyword(s):  
Diastolic Pressure ◽  
Arterial Compliance ◽  
Aortic Pressure ◽  
Arterial System ◽  
Windkessel Model ◽  
Total Arterial Compliance ◽  
Improved Methods ◽  
Mean Aortic Pressure

Determination of arterial compliance in vivo has long interested physiologists. Most current methods for estimating this parameter assume that compliance is constant, i.e., that arterial pressure-volume (P-V) relations are linear, and they also assume that diastolic aortic pressure decay is an exponential function of time. Both of these assumptions, however, are questionable. This study proposes improved methods of estimating compliance based on a Windkessel model of the arterial system but which utilize the area under the pressure tracing rather than the waveform itself. Formulations accounting for both linear and three hypothetical nonlinear arterial P-V relations (exponential, logarithmic, and parabolic) are presented. Data from patients with congestive heart failure and hypertension are used for illustration. Compliances assuming linear P-V relations are reasonably close to those assuming nonlinear P-V relations only at mean aortic pressure. At end-diastolic pressure the linear assumption underestimates and at peak systolic it overestimates the compliances obtained assuming nonlinear P-V relations. The simpler linear assumption still allows a first approximation to compliance, but we show that existing methods for obtaining compliance under this assumption have severe theoretical as well as practical shortcomings. Our proposed method avoids these shortcomings primarily because deviations from an exact exponential form of the pressure wave have less influence on these compliance estimates than currently used methods.

scholarly journals Positron Emission Tomography Compartmental Models: A Basis Pursuit Strategy for Kinetic Modeling

2002 ◽  
Vol 22 (12) ◽  
pp. 1425-1439 ◽  
Author(s):  
Roger N. Gunn ◽  
Steve R. Gunn ◽  
Federico E. Turkheimer ◽  
John A. D. Aston ◽  
Vincent J. Cunningham
Keyword(s):  
Positron Emission Tomography ◽  
Kinetic Modeling ◽  
Impulse Response Function ◽  
Emission Tomography ◽  
Basis Pursuit ◽  
Parameter Estimates ◽  
Binding Studies ◽  
General Applicability ◽  
Positron Emission

A kinetic modeling approach for the quantification of in vivo tracer studies with dynamic positron emission tomography (PET) is presented. The approach is based on a general compartmental description of the tracer's fate in vivo and determines a parsimonious model consistent with the measured data. The technique involves the determination of a sparse selection of kinetic basis functions from an overcomplete dictionary using the method of basis pursuit denoising. This enables the characterization of the systems impulse response function from which values of the systems macro parameters can be estimated. These parameter estimates can be obtained from a region of interest analysis or as parametric images from a voxel-based analysis. In addition, model order estimates are returned that correspond to the number of compartments in the estimated compartmental model. Validation studies evaluate the methods performance against two preexisting data led techniques, namely, graphical analysis and spectral analysis. Application of this technique to measured PET data is demonstrated using [11C]diprenorphine (opiate receptor) and [11C]WAY-100635 (5-HT1A receptor). Although the method is presented in the context of PET neuroreceptor binding studies, it has general applicability to the quantification of PET/SPECT radiotracer studies in neurology, oncology, and cardiology.

Safety Considerations for Sample Analysis Using a Near-Infrared (785 nm) Raman Laser Source

2003 ◽  
Vol 57 (5) ◽  
pp. 580-587 ◽  
Author(s):  
S. D. Harvey ◽  
T. J. Peters ◽  
B. W. Wright
Keyword(s):  
Near Infrared ◽  
Energetic Material ◽  
Experimental Studies ◽  
Thermal Response ◽  
Raman Laser ◽  
Medical Diagnostics ◽  
Laser Source ◽  
Analytical Technique ◽  
Nir Laser

Raman spectroscopy is often considered a nondestructive analytical technique; however, this is not always the case. The 300-mW 785-nm near-infrared (NIR) laser source used with many commercially available instruments has sufficient power to burn samples. This destructive potential is of special concern if the sample is irreplaceable (e.g., fine art, forensic evidence, or for in vivo medical diagnostics) or a hazardous energetic material (explosive or pyrophoric samples). This study quantifies the heat resulting from illuminating an extensive color array with a 785-nm NIR laser and relates these values to the hazards associated with Raman analysis. In general, darker colors were found to be more problematic. Since visible colors are not ideally correlated with absorptive characteristics at 785 nm, predictions based on thermography are not perfect; however, this approximation gives a useful method for predicting the thermal response of unknown samples to NIR exposure. Additionally, experimental studies evaluated the analysis of flammable organic solvents, propellants, military explosives, mixtures containing military explosives, shock-sensitive explosives, and gunpowders (i.e., smokeless, black, and Pyrodex powders). Safety guidelines for analysis are presented.

An In Vivo Method for Measuring Turbulence in Mechanical Prosthesis Leakage Jets

2004 ◽  
Vol 126 (1) ◽  
pp. 26-35 ◽  
Author(s):  
Brandon R. Travis ◽  
Thomas D. Christensen ◽  
Morten Smerup ◽  
Morten S. Olsen ◽  
J. Michael Hasenkam ◽  
...  
Keyword(s):  
Mechanical Heart Valve ◽  
Maximum Velocity ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Mechanical Prosthesis ◽  
Analytical Technique ◽  
In Vivo Measurement ◽  
Measurement And Analysis

This work introduces a method for the in vivo measurement and analysis of turbulence within the leakage of a mechanical heart valve. Several analysis techniques were applied to ultrasound measurements acquired within the atrium of a pig, and error associated with these techniques was analyzed. The technique chosen applies cyclic averaging to mean and maximum velocity measurements within small, normalized phase windows to calculate Reynolds normal stresses in the direction of the ultrasound beam. Maximum shear stresses are estimated from these normal stresses using an analytical technique. The stresses observed were smaller than those reported from previous in vitro simulations.

scholarly journals Integrated methodology to calculate nonsinusoidal AC systems of high frequency

Vestnik IGEU ◽  
2021 ◽  
pp. 40-54
Author(s):  
A.V. Gusenkov ◽  
A.A. Dyachkov ◽  
V.D. Lebedev ◽  
A.M. Sokolov ◽  
T.E. Shadrikov
Keyword(s):  
Power Supply ◽  
High Frequency ◽  
Research Work ◽  
Internal Resistance ◽  
Analytical Technique ◽  
Operating Modes ◽  
Electrical Systems ◽  
Ac Systems ◽  
Cable Lines ◽  
High Frequency Ac

During the research and development of fundamentally new AC systems of high frequency, the authors identified the problems of the calculations and modeling of the operating modes of such systems according to the method of Yu.M. Osipova. Application of the method gives results that are significantly different from the experimental ones. The aim of the study is to improve the methodology considering the features of high-frequency electrical systems, their topology, and components. The research has been carried out based on a mathematical model of an electrical system of high frequency, which includes a power supply, matching transformers, cable lines and a load. The power supply is modeled in a simplified form with the internal resistance of the transistors. An analytical technique for calculating and modeling high-frequency AC systems has been developed. Analytical expressions are presented to calculate the characteristics and parameters of the high frequency system components. Recommendations on automation of the developed technique using MATLAB, Python or Simulink are presented.Comparison of the results of calculation and the experiment is carried out to confirm the reliability. The results of the research work can be used for modeling and calculating high frequency alternating current systems to determine the current load, voltage levels, analyze overvoltages and emergency modes.

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