Assessment of Fiber Strength in a Urinary Bladder by Using Experimental Pressure Volume Curves: An Analytical Method

1986 ◽  
Vol 108 (4) ◽  
pp. 301-305 ◽  
Author(s):  
A. To¨zeren
Keyword(s):  
Urinary Bladder ◽  
Analytical Method ◽  
Fiber Strength ◽  
Rate Of Change ◽  
Chamber Pressure ◽  
Fiber Stress ◽  
Chamber Volume ◽  
Volume Relation ◽  
Fiber Reinforced Material ◽  
Biochemical Activation

In the present study, an analytical method is developed to deduce the constitutive equations of fibers embedded in a thick shell from the time-variant pressure volume curves obtained by experimental procedures. It is assumed that the spherical shell under consideration is composed of a fiber reinforced material and undergoes radial deflection, modeling the behavior of some biological shells such as urinary bladder. The fiber stress is expressed as a function of fiber strain, rate of strain and the degree of biochemical activation. The function form is chosen such that equations of mechanical equilibrium can be integrated analytically to yield chamber pressure as a function of chamber volume, time rate of change of volume and activation. Arbitrary coefficients appearing in the fiber stress-equation are also present in the resultant time-variant pressure-volume relation. These coefficients can be determined by curve-fitting commonly used clinical data such as cystometry measurements.

Modeling the contractility of urinary bladder smooth muscle using isometric contractions

1986 ◽  
Vol 251 (5) ◽  
pp. R978-R983
Author(s):  
R. van Mastrigt ◽  
J. W. Koopal ◽  
J. Hak ◽  
J. van de Wetering
Keyword(s):  
Smooth Muscle ◽  
Urinary Bladder ◽  
Tissue Sample ◽  
Rate Of Change ◽  
Isometric Contractions ◽  
Bladder Smooth Muscle ◽  
Straight Line ◽  
Urinary Bladder Smooth Muscle ◽  
Rest Time ◽  
Two Parameters

In the course of developing a clinical contractility index, isometric contractions of pig urinary bladder smooth muscle were analyzed in terms of phase plots (a plot of the rate of change of a variable, in this case force, as a function of the variable itself). The straight line describing the major part of the phase plots is characterized by the two parameters Fiso (the horizontal intercept) and c (the slope) of the line. It was found that changes in the geometry of the tissue sample and changes in extracellular calcium grossly influence Fiso, but not c, whereas changes in prestimulus rest time influence c, but not Fiso. It is concluded that Fiso is related to the number of available contractile units, and c is related to the limiting rate constant in the excitation-contraction coupling, which is probably determined by the release of intracellular calcium. The existence of the calcium paradox and the interpretation of the concept of facilitation or potentiation in this type of smooth muscle are discussed.

A critical magma chamber size for volcanic eruptions

Geology ◽  
2020 ◽  
Vol 48 (5) ◽  
pp. 431-435 ◽  
Author(s):  
Meredith Townsend ◽  
Christian Huber
Keyword(s):  
Magma Chamber ◽  
Scaling Law ◽  
Volcanic Eruptions ◽  
Elastic Response ◽  
Chamber Pressure ◽  
Pressure Drops ◽  
Chamber Volume ◽  
Intermediate Chamber ◽  
History Of ◽  
Chamber Size

Abstract We present a model for a coupled magma chamber–dike system to investigate the conditions required to initiate volcanic eruptions and to determine what controls the size of eruptions. The model combines the mechanics of dike propagation with internal chamber dynamics including crystallization, volatile exsolution, and the elastic response of the magma and surrounding crust to pressure changes within the chamber. We find three regimes for dike growth and eruptions: (1) below a critical magma chamber size, eruptions are suppressed because chamber pressure drops to lithostatic before a dike reaches the surface; (2) at an intermediate chamber size, the erupted volume is less than the dike volume (“dike-limited” eruption regime); and (3) above a certain chamber size, dikes can easily reach the surface and the erupted volume follows a classic scaling law, which depends on the attributes of the magma chamber (“chamber-limited” eruption regime). The critical chamber volume for an eruption ranges from ∼0.01 km3 to 10 km3 depending on the water content in the magma, depth of the chamber, and initial overpressure. This implies that the first eruptions at a volcano likely are preceded by a protracted history of magma chamber growth at depth, and that the crust above the magma chamber may have trapped several intrusions or “failed eruptions.” Model results can be combined with field observations of erupted volume, pressure, and crystal and volatile content to provide tighter constraints on parameters such as the eruptible chamber size.

scholarly journals A Semilinear Parameter-Varying Observer Method for Fabric-Reinforced Soft Robots

2021 ◽  
Vol 8 ◽  
Author(s):  
Phuc D.H. Bui ◽  
Joshua A. Schultz
Keyword(s):  
Configuration Space ◽  
Controller Design ◽  
Ground Truth ◽  
Rate Of Change ◽  
Contact Forces ◽  
Chamber Pressure ◽  
Soft Robot ◽  
Linear Parameter Varying ◽  
Final Model ◽  
Parameter Varying

This paper presents an observer architecture that can estimate a set of configuration space variables, their rates of change and contact forces of a fabric-reinforced inflatable soft robot. We discretized the continuum robot into a sequence of discs connected by inextensible threads; this allows great flexibility when describing the robot’s behavior. At first, the system dynamics is described by a linear parameter-varying (LPV) model that includes a set of subsystems, each of which corresponds to a particular range of chamber pressure. A real-world challenge we confront is that the physical robot prototype exhibits a hysteresis loop whose directions depend on whether the chamber is inflating or deflating. In this paper we transform the hysteresis model to a semilinear model to avoid backward-in-time definitions, making it suitable for observer and controller design. The final model describing the soft robot, including the discretized continuum and hysteresis behavior, is called the semilinear parameter-varying (SPV) model. The semilinear parameter-varying observer architecture includes a set of sub-observers corresponding to the subsystems for each chamber pressure range in the SPV model. The proposed observer is evaluated through simulations and experiments. Simulation results show that the observer can estimate the configuration space variables and their rate of change with no steady-state error. In addition, experimental results display fast convergence of generalized contact force estimates and good tracking of the robot’s configuration relative to ground-truth motion capture data.

Active and passive stresses in the myocardium

2000 ◽  
Vol 279 (5) ◽  
pp. H2519-H2528 ◽  
Author(s):  
Rachad M. Shoucri
Keyword(s):  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Cardiac Contraction ◽  
Ventricular Wall ◽  
Fiber Stress ◽  
Active Fiber ◽  
Force Unit ◽  
Volume Relation ◽  
Detailed Interpretation ◽  
Passive Stress

A mathematical approach that can be used to calculate the passive stress in the ventricular wall is presented. The active fiber stress (force/unit area) generated by the muscular fibers in the ventricular wall is expressed by means of body force (force/unit volume of the myocardium). It is shown that the total intramyocardial passive stress induced in the passive medium of the myocardium can be expressed as the sum of a passive stress induced by the left ventricular pressure and a passive stress induced by the active fiber stress. Applications to experimental data published in the literature are given. New results are presented that show the relation among those two components of the intramyocardial passive stress. New relations between the intramyocardial passive stress, the slope (elastance) of the pressure-volume relation, and the residual volume are also derived. The results obtained give a better understanding of some aspects of the mechanics of cardiac contraction and can provide a more detailed interpretation of clinical conditions.

scholarly journals A Novel Model of Pressure Decay in Pressure-Driven Membrane Integrity Tests Based on the Bubble Dynamic Process

2019 ◽  
Vol 9 (2) ◽  
pp. 273
Author(s):  
Songlin Wang ◽  
Jiaqi Ding ◽  
Han Xu ◽  
Pengchao Xie ◽  
Junfeng Wu ◽  
...  
Keyword(s):  
Dynamic Process ◽  
Accurate Determination ◽  
Membrane Integrity ◽  
Defect Size ◽  
Chamber Pressure ◽  
Bubble Dynamic ◽  
Pressure Decay ◽  
Chamber Volume ◽  
Decay Test ◽  
Gas Chamber

The membrane integrity is estimated using a pressure decay test based on the bubble dynamic process of membrane defects. The present work builds a schematic diagram for a bubble formation model of a pressure decay test, proposes a simulation model of pressure decay rate (PDR) in the membrane gas chamber by means of numerical simulation using microdefect bubble dynamic behavior, and tries to establish the main factors influencing the back-calculated defect size resolution. Results obtained from the variations in the membrane gas chamber pressure and the PDR allowed for accurate determination of the membrane defect size, and the PDR was found to be relatively dependent on the gas chamber volume and the initial applied test pressure. The measured data about PDR using controlled experimental parameters was in good agreement with the trend found in the prediction model, proving that the pressure decay test process is in essence a bubble dynamic process. Furthermore, the back-calculated defect size resolution was found to decrease with the increase in gas chamber volume and PDR as well as with the decrease in applied pressure.

Functional capacity of nicotine-sensitive canine intrinsic cardiac neurons to modify the heart

1994 ◽  
Vol 266 (4) ◽  
pp. R1127-R1135 ◽  
Author(s):  
D. A. Murphy ◽  
S. O'Blenes ◽  
B. D. Hanna ◽  
J. A. Armour
Keyword(s):  
Heart Rate ◽  
Nervous System ◽  
Cardiac Myocyte ◽  
Sympathetic Neurons ◽  
Power Spectral Analysis ◽  
Left Ventricular ◽  
Rate Of Change ◽  
Chamber Pressure ◽  
Adrenergic Blockade ◽  
Before And After

The capacity of intrinsic cardiac efferent parasympathetic and sympathetic neurons to modify the heart was investigated in nine anesthetized open-chest dogs with adrenal glands removed from the circulation. The effects elicited by intravenously administered isoproterenol, tyramine, and nicotine on cardiac variables were examined before and after acute decentralization of the heart. Major vessels, as well as other tissues at the base of the heart, were denuded by means of an ultrasonic aspirator that removed neural elements without damaging muscles or blood vessels. The efficacy of the acute decentralization was assured by testing cardiac responses elicited by right and left stellate ganglia and cervical vagosympathetic complex stimulations after surgery. Heart rate, atrial force, and both right and left ventricular intramyocardial systolic pressures were augmented similarly by isoproterenol and tyramine before and after acute decentralization, indicating that the surgery necessary to decentralize the heart did not obtund cardiac myocyte function. Power spectral analysis of heart rate and left ventricular chamber pressure rate of change indicated an almost complete lack of variability of these indexes after, but not before, acute decentralization. Despite these changes, similar cardiac augmentation was elicited by nicotine before and after acute decentralization. Cardiac augmentation was elicited by nicotine in acutely decentralized preparations after atropine administration but not after beta-adrenergic blockade. These data indicate that the canine intrinsic cardiac nervous system contains a significant population of nicotine-sensitive adrenergic neurons that modulate the heart. Furthermore, the intrinsic cardiac nervous system does not appear to be primarily responsible for the heart rate and ventricular pressure variability found in intact hearts.

Modification of epithelial permeability by cationic polypeptides

1993 ◽  
Vol 265 (6) ◽  
pp. C1637-C1647 ◽  
Author(s):  
C. J. Tzan ◽  
J. R. Berg ◽  
S. A. Lewis
Keyword(s):  
Amino Acids ◽  
Urinary Bladder ◽  
Charge Density ◽  
Apical Membrane ◽  
Density Ratio ◽  
Membrane Conductance ◽  
Rate Of Change ◽  
Total Charge ◽  
Bladder Epithelium ◽  
Anion Conductance

It has been demonstrated that protamine sulfate (PS; a cationic polypeptide composed of 70% arginine) increases the apical membrane conductance of the mammalian urinary bladder. In this report, synthetic cationic polypeptides (CpP; e.g., polyarginine) were used to determine whether the response of the bladder to PS was due to its cationic nature (i.e., its arginine content). We demonstrate that CpP induce a large increase in the cation and anion conductance of the apical membrane of the rabbit urinary bladder epithelium. The modulation of the membrane conductance by CpP is dependent upon a number of parameters. 1) The magnitude of the conductance change was voltage dependent. 2) An increase in the total charge per molecule increased the rate of conductance change. 3) An increase in the charge density (ratio of charged amino acids to total amino acids) increased the rate of change of conductance. 4) La3+ inhibited the ability of CpP to alter the membrane conductance. 5) The rate of reversal of the CpP-induced conductance was dependent upon the total charge per molecule as well as the charge density. 6) The level of self-inhibition (ability of solution CpP to inhibit the CpP-induced membrane conductance) was inversely correlated with the charge density and was also concentration dependent, with less inhibition occurring at low mucosal CpP concentrations. These data are consistent with a model developed to describe the effect of PS on the conductive properties of the urinary bladder epithelium.

The process of urinary bladder cancer recurrence in 33 patients with 113 tumors, analyzed by changes in IHC features of 80 pairs of subsequent tumors.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. e16507-e16507
Author(s):  
Sven Kurbel ◽  
Branko Dmitrovic ◽  
Mate Matić ◽  
Damir Vrbanec
Keyword(s):  
Bladder Cancer ◽  
Urinary Bladder ◽  
Cancer Recurrence ◽  
Urinary Bladder Cancer ◽  
Rate Of Change ◽  
Ki 67 ◽  
Female Patients ◽  
Recurrent Tumors ◽  
Em Clustering ◽  
Bladder Cancer Recurrence

e16507 Background: The aim was to define IHC changes between the two subsequent urinary bladder cancers (UBC). Methods: IHC data on EGFR, HER2, HER3, Ki-67, MLH1, MSH2, MSH6 and PMS2 in 113 UHC from 24 male and 9 female patients (1 to six recurrences) were used. Except for the Ki-67 value, other markers were stratified: “0” for no positive cells; “1” < = 10% positive cells; “2” 1%-30% positive cells; and “3” 31%-100% positive cells. Data of consecutive tumors were paired in 80 processes of recurrence (PoR). Changes between the latter and the former tumor were calculated: in +/- % for Ki-67 values, and as integer sums of absolute changes in expression for HER markers and for Lynch markers. EM clustering was applied for recognition of relevant IHC changes. Results: Three aspects were tested: the speed of recurrence, was it the first, or later recurrence and whether PoRs depended on the total number of tumors in that patient. Early and late PoRs clustered along the Lynch score, while the intermediate clustered along the delta Ki-67 value. The first PoRs clustered along the HER score and all subsequent PoRs depended on the Lynch score. Conclusions: Even in this limited group of patients Lynch and HER markers showed complex differences between early and late recurrent tumors. The speed of the recurrence and changes of IHC features depended mainly on the rate of change in Lynch markers, suggesting that they should be tested as predictors of UBC recurrence.[Table: see text]

Densitometric Identification of Primitive Erythroblasts After Reaction With Diaminobenzidine

1973 ◽  
Vol 31 ◽  
pp. 328-329
Author(s):  
John A. Trotter
Keyword(s):  
Red Blood Cells ◽  
Analytical Method ◽  
Blood Cells ◽  
Guinea Pigs ◽  
Specific Protein ◽  
Visual Examination ◽  
Hemoglobin Synthesis ◽  
Peroxidatic Activity ◽  
Small Density

Hemoglobin is the specific protein of red blood cells. Those cells in which hemoglobin synthesis is initiated are the earliest cells that can presently be considered to be committed to erythropoiesis. In order to identify such early cells electron microscopically, we have made use of the peroxidatic activity of hemoglobin by reacting the marrow of erythropoietically stimulated guinea pigs with diaminobenzidine (DAB). The reaction product appeared as a diffuse and amorphous electron opacity throughout the cytoplasm of reactive cells. The detection of small density increases of such a diffuse nature required an analytical method more sensitive and reliable than the visual examination of micrographs. A procedure was therefore devised for the evaluation of micrographs (negatives) with a densitometer (Weston Photographic Analyzer).

Residual Gas Reaction in the Electron Microscope: II The Design of a Gas-Control Chamber for Quantitative Observations

1969 ◽  
Vol 27 ◽  
pp. 82-83
Author(s):  
Chester J. Calbick ◽  
Richard E. Hartman
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Local Environment ◽  
Chamber Pressure ◽  
Objective Lens ◽  
Ion Pump ◽  
Quantitative Studies ◽  
Precise Knowledge ◽  
Differential Pumping ◽  
And Control

Quantitative studies of the phenomenon associated with reactions induced by the electron beam between specimens and gases present in the electron microscope require precise knowledge and control of the local environment experienced by the portion of the specimen in the electron beam. Because of outgassing phenomena, the environment at the irradiated portion of the specimen is very different from that in any place where gas pressures and compositions can be measured. We have found that differential pumping of the specimen chamber by a 4" Orb-Ion pump, following roughing by a zeolite sorption pump, can produce a specimen-chamber pressure 100- to 1000-fold less than that in the region below the objective lens.

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