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Internal pressure
About: Internal pressure is a research topic. Over the lifetime, 7416 publications have been published within this topic receiving 61580 citations.
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TL;DR: In this article, the authors conducted multi-anvil experiments at simultaneous high pressures and temperatures using multiple internal pressure standards including Au, Pt, MgO, W, Mo, Pd, and Ag.
143 citations
TL;DR: It is shown that, unlike unpressurized shells, the relationship between force and displacement demonstrates two linear regimes, and it is inferred that the internal osmotic pressure of yeast cells may be regulated in response to changes in the osmosis pressure of the external medium.
Abstract: Pressurized elastic capsules arise at scales ranging from the 10 m diameter pressure vessels used to store propane at oil refineries to the microscopic polymeric capsules that may be used in drug delivery. Nature also makes extensive use of pressurized elastic capsules: plant cells, bacteria and fungi have stiff walls, which are subject to an internal turgor pressure. Here, we present theoretical, numerical and experimental investigations of the indentation of a linearly elastic shell subject to a constant internal pressure. We show that, unlike unpressurized shells, the relationship between force and displacement demonstrates two linear regimes. We determine analytical expressions for the effective stiffness in each of these regimes in terms of the material properties of the shell and the pressure difference. As a consequence, a single indentation experiment over a range of displacements may be used as a simple assay to determine both the internal pressure and elastic properties of capsules. Our results are relevant for determining the internal pressure in bacterial, fungal or plant cells. As an illustration of this, we apply our results to recent measurements of the stiffness of baker's yeast and infer from these experiments that the internal osmotic pressure of yeast cells may be regulated in response to changes in the osmotic pressure of the external medium.
142 citations
TL;DR: In this paper, the critical internal pressure P at which a circular debond blister will grow in size, in terms of the tensile modulus E and thickness t of an adhering layer, and the strength G sub a of its adhesion to a rigid substrate.
Abstract: : An analysis is given of the critical internal pressure P at which a circular debond blister will grow in size, in terms of the tensile modulus E and thickness t of an adhering layer, and the strength G sub a of its adhesion to a rigid substrate. Measurements of blow-off pressure are reported for adhering layers of pressure-sensitive tapes having widely-different effective modulus and thickness, and with blisters having a range of diameters. Satisfactory agreement is obtained with the theoretical predictions, suggesting that the theory is basically correct in assuming that relatively thin layers behave like elastic membranes. Attention is drawn to the unusual form of the dependence of the debonding pressure P upon the resistance Et of the layer to stretching and upon the detachment energy . Even though the adhering layer is assumed to be linearly- elastic, the markedly non-linear (cubic)relation between pressure P and volume V of the blister, or maximum height y, leads to this unusual result. The detachment energy is given by a particularly simple function of the pressure P and maximum deflection of the blister: G sub a = 0.65 Py, independent of the stiffness of the adhering layer and diameter of the blister.
142 citations
TL;DR: In this paper, the authors deal with finite element analysis of closed membrane structures that contain an enclosed fluid such as air, and the change in the fluid pressure resulting from the application of external forces is evaluated and taken into account in the formulation of the equilibrium equations.
141 citations
TL;DR: The finger blood pressure monitor measures blood pressure continuously and noninvasively by means of a technique described by J. Peňaz, and algorithms determine the unloaded artery size approximately every minute and automatically correct for changes possibly induced by smooth muscle contraction or relaxation.
Abstract: The finger blood pressure monitor measures blood pressure continuously and noninvasively by means of a technique described by J. Penaz. The size of the artery is measured when its internal pressure (arterial pressure) equals the external pressure. (At this point, transmural pressure equals zero and the arterial wall is said to be "unloaded.") This unloaded condition is maintained by continuous, automatic adjustments of external pressure on the artery, adjustments that are made simultaneously with and parallel to intraarterial pressure variations. The external pressure then constantly equals internal pressure (arterial blood pressure) and is reported by the monitor as values for systolic, mean, and diastolic pressure. A finger cuff with a built-in light source and detector is used to measure finger artery size, and an inflatable bladder is used to apply the external pressure to the artery. The monitor is microprocessor based; algorithms determine the unloaded artery size approximately every minute and automatically correct for changes possibly induced by smooth muscle contraction or relaxation, and a high-speed electropneumatic servo control system enables automatic calibration and adjustment.
139 citations