Search results for "contraction"

Response of human ventricular heart muscle to histamine

1981

Zur Frage der Beziehungen zwischen enddiastolischem Ventrikeldruck unddp/dt bzw.d 2 p/dt 2 der Ventrikeldruckkurve des Herzens

1969

Correlations between left ventricular enddiastolic pressure of the heart and first and second derivation of left ventricular pressure curve (dp/dt, d2p/dt2 respectively) were examined at various hemodynamic conditions. The results showed only a particular dependence ofdp/dt andd2p/dt2 from enddiastolic pressure. Therefore, it is concluded, that enddiastolic pressure is not the most important factor, which influences the dynamics of ventricular contraction.

Relaxant effects of antidepressants on human isolated mesenteric arteries

1999

Aims The therapeutic action of tricyclic agents may be accompanied by unwanted effects on the cardiovascular system. The evidence for the effects on vascular and nonvascular smooth muscle comes from animal studies. Whether these studies can be extrapolated to human vessels remains to be determined. Therefore, the present study was designed to investigate the influence of amitriptyline, nortriptyline and sertraline on the contractile responses of human isolated mesenteric arteries to electrical field stimulation, noradrenaline and potassium chloride. Methods Arterial segments (lumen diameter 0.8–1.2 mm) were obtained from portions of the human omentum during the course of 41 abdominal operat…

Elektrische Registrierung der Druckanstiegsbeschleunigung und ihre Beziehung zur isometrischen Kontraktion des linken Herzventrikels

1967

Aus der zweimaligen Differentiation der Ventrikeldruckkurve nach der Zeit ergibt sich die Druckanstiegsbeschleunigung. Dieser Parameter wurde mittels RC-Glieder bei der Kontraktion des linken Ventrikels der Katze registriert. Sein Maximum lag in der Phase der isometrischen Kontraktion. Die maximale Druckanstiegsbeschleunigung nahm bei Erhohung der isometrischen Kontraktion starker zu als die maximale Druckanstiegsgeschwindigkeit. Es wird gefolgert, das zwischen der Kraft der isometrischen Kontraktion und der maximalen Druckanstiegsbeschleunigung eine Proportionalitat besteht.

Effect of angular velocity on soleus and medial gastrocnemius H-reflex during maximal concentric and eccentric muscle contraction.

2009

At rest, the H-reflex is lower during lengthening than shortening actions. During passive lengthening, both soleus (SOL) and medial gastrocnemius (MG) H-reflex amplitudes decrease with increasing angular velocity. This study was designed to investigate whether H-reflex amplitude is affected by angular velocity during concentric and eccentric maximal voluntary contraction (MVC). Experiments were performed on nine healthy men. At a constant angular velocity of 60 degrees /s and 20 degrees /s, maximal H-reflex and M-wave potentials were evoked at rest (i.e., H(max) and M(max), respectively) and during concentric and eccentric MVC (i.e., H(sup) and M(sup), respectively). Regardless of the muscl…

Limits of lateral expansion in two-dimensional materials with line defects

2021

The flexibility of two-dimensional (2D) materials enables static and dynamic ripples that are known to cause lateral contraction, shrinking of the material boundary. However, the limits of 2D materials' \emph{lateral expansion} are unknown. Therefore, here we discuss the limits of intrinsic lateral expansion of 2D materials that are modified by compressive line defects. Using thin sheet elasticity theory and sequential multiscale modeling, we find that the lateral expansion is inevitably limited by the onset of rippling. The maximum lateral expansion $\chi_{max}\approx 2.1\cdot t^2\sigma_d$, governed by the elastic thickness $t$ and the defect density $\sigma_d$, remains typically well belo…

Feynman graph polynomials

2010

The integrand of any multi-loop integral is characterised after Feynman parametrisation by two polynomials. In this review we summarise the properties of these polynomials. Topics covered in this article include among others: Spanning trees and spanning forests, the all-minors matrix-tree theorem, recursion relations due to contraction and deletion of edges, Dodgson's identity and matroids.

Integration of massive states as contractions of non linear sigma-models

2005

We consider the contraction of some non linear sigma models which appear in effective supergravity theories. In particular we consider the contractions of maximally symmetric spaces corresponding to N=1 and N=2 theories, as they appear in certain low energy effective supergravity actions with mass deformations. The contraction procedure is shown to describe the integrating out of massive modes in the presence of interactions, as it happens in many supergravity models after spontaneous supersymmetry breaking.

Deformations of Differential Calculi

1996

It has been suggested that quantum fluctuations of the gravitational field could give rise in the lowest approximation to an effective noncommutative version of Kaluza-Klein theory which has as extra hidden structure a noncommutative geometry. It would seem however from the Standard Model, at least as far as the weak interactions are concerned, that a double-sheeted structure is the phenomenologically appropriate one at present accelerator energies. We examine here to what extent this latter structure can be considered as a singular limit of the former.

Mechanical and electrical behavior of human muscle during maximal concentric and eccentric contractions

1974

The force-velocity relationships of human muscle (e.g., Asmussen, Hansen, and Lammert, 1965; Komi, 1973a) characterize the main mechanical differences in concentric and eccentric work. Some information also has been reported on the interrelationship between neural input and mechanical output during submaximal concentric and eccentric contractions. The slope of the regression line representing the relationship between IEMG and muscle tension is greater when muscle shortens at a constant velocity than when it lengthens at the same velocity (Bigland and Lippold, 1954). When recordings were made with a greater number of velocities, then a family of curves was obtained, a result which emphasizes…