Negative Pressure In Liquids Research Articles

Molecular Dynamics Study on the Storage of Carbon Dioxide in Single-Walled Carbon Nanotubes at Low Pressures.

The storage of carbon dioxide (CO2) in single-walled carbon nanotubes was studied with molecular dynamics simulation. The influences of the temperature, system average density, and nanotube size on the CO2 pressure, density distribution, and intermolecular forces were investigated. Multilayer adsorption inside nanotubes was observed as average density increases at lower pressures, which is desirable in industry. Meanwhile, a nanobubble was gradually formed in the center of the nanotube, and the system with the nanobubble was stabilized by the balance between the positive Laplace pressure and the negative liquid pressure when the size of the nanobubble was higher than the critical size. The adsorption effect of the nanotube wall leads to high local condensed density near the wall and stronger intermolecular repulsion, while Laplace pressure results in a low local condensed density in the adsorbed CO2 near the bubble interface and stronger intermolecular attraction. The stretching effect that originates from the intermolecular force dominated by attraction in the condensed phase leads to low pressure. At the critical nanobubble size, a higher CO2 average density can be achieved by lowering the temperature and increasing the nanotube radius or length. When the adsorption impact of the nanotube wall on bubble destabilization becomes negligible as the adsorption layer thickens, further increasing the nanotube radius leads to limited increase of the average density at the critical nanobubble size. The simulation of a graphene-sealed nanotube confirmed the formation of a vapor nanobubble under more realistic conditions. This work provides insights into utilizing carbon nanotubes as a material for CO2 capture with multilayer adsorption at lower pressures.

Lipid-Coated Nanobubbles in Plants.

One of the more surprising occurrences of bulk nanobubbles is in the sap inside the vascular transport system of flowering plants, the xylem. In plants, nanobubbles are subjected to negative pressure in the water and to large pressure fluctuations, sometimes encompassing pressure changes of several MPa over the course of a single day, as well as wide temperature fluctuations. Here, we review the evidence for nanobubbles in plants and for polar lipids that coat them, allowing nanobubbles to persist in this dynamic environment. The review addresses how the dynamic surface tension of polar lipid monolayers allows nanobubbles to avoid dissolution or unstable expansion under negative liquid pressure. In addition, we discuss theoretical considerations about the formation of lipid-coated nanobubbles in plants from gas-filled spaces in the xylem and the role of mesoporous fibrous pit membranes between xylem conduits in creating the bubbles, driven by the pressure gradient between the gas and liquid phase. We discuss the role of surface charges in preventing nanobubble coalescence, and conclude by addressing a number of open questions about nanobubbles in plants.

Simulation study on the effect of resistance exercise on the hydrodynamic microenvironment of osteocytes in microgravity

Osteoporosis occurs in astronauts after long-term space flight owing to the lack of gravity. The mechanical microenvironment of osteocytes in load-bearing bone are changed during resistance exercise, which prevents massive bone loss in the human body. A cylindrical fluid-structure coupling finite element model for osteons with a two-stage pore structure (i.e., Haversian canal, lacunar-canalicular system) was established with the software COMSOL. In the Earth’s gravity field and in microgravity, considering the effects of pulsating pressure of arterioles, a comparative study was performed on the changes in hydrodynamic microenvironment of osteocytes during human body high-intensity exercise at different frequencies (defined as causing bone to produce 3000 με) and the body is at rest. Positive and negative liquid pressure (with respect to one atmosphere pressure) alternately acted on osteocytes during human exercising, but only positive pressure acted on osteocytes during human resting. The variation range of liquid pressure acted on osteocytes during human exercising was significantly higher than that during resting. The liquid flow velocity around osteocytes during body exercise was about four orders of magnitude higher than that during resting. In microgravity, moderate physical exercise can obviously improve the hydrodynamic microenvironment of osteocytes in load-bearing bone, which could compensate for the lack of mechanical stimulation to osteocytes caused by the lack of gravity, thereby promoting the normal physiological function of osteocytes. To a certain extent, these results revealed the biomechanical mechanism by which exercise has an effect in fighting osteoporosis in astronauts.

Influence of different confining matrices on negative pressure in liquid n-heptane investigated using positronium bubbles as a probe

HypothesisThe negative pressure in liquids under the concave meniscus of nanometer size can be observed experimentally. This allows verification of the predictions of the macroscopic Young-Laplace law, which has so far been performed only on the basis of theoretical calculations. The deviation of the negative pressure from the Young-Laplace law allows to get information about the structure of the porous matrix. ExperimentsThe properties of n-heptane confined in nanometer-sized spaces are monitored in situ due to the particular ability of positronium to form subnanometer bubbles in liquids. Positron annihilation lifetime spectroscopy allows to detect their sizes, which in turn are used to determine surface tension and negative pressure of the investigated liquid. These results are obtained by means of an improved quantum-mechanical model approximating the o-Ps bubble with a 1.3 eV finite potential well. FindingsThe dependence of the negative pressure on the curvature of the concave meniscus is found, which follows the Young-Laplace law with a good accuracy for model cylindrical pores. The differences between the pressure in the liquid confined in pores of various sizes and shapes in different materials allow inference about several phenomena (e.g. pore blocking in materials with a complex pore structure or swelling of the polymer).

Growing Negative Pressure in Dissolved Solutes: Raman Monitoring of Solvent-Pulling Effect

Negative pressure in liquids is both an experimental fact and a usually neglected state of condensed matter. Using synthetic fluid inclusions, namely closed vacuoles fabricated inside one solid host by hydrothermal processes, a Raman study was performed to examine how a superheated solvent (under negative pressure) interacts with its dissolved solutes. As a result, this contribution not only illustrates this well-known tensile state but also displays evidence that a stretched solvent is able to pull on its dissolved solutes and put them also under a stretched state. The dielectric continuum hypothesis may lead to expect a stretching effect in solutes similar to the solvent’s, but our measurements evidence a damping mechanical effect (growing with tension), most probably related to solvation shells. One practical consequence is that the (experimentally known) supersolvent properties of superheated solutions are certainly related to the change of the chemical potential of solutes which results from the damp...

Heat transfer characteristics and pressure variation in a nanoscale evaporating meniscus

A nanoscale evaporating meniscus is simulated in this work using molecular dynamics. The heat and mass transfer characteristics and pressure variation in the non-evaporating and interline regions are studied. Very high heat and evaporation flux rates of the order of 100 MW/m 2 and 1000 kg/m 2 s, respectively, are achieved. The disjoining pressure increased significantly after the formation of the non-evaporating film. High negative liquid pressure induced due to capillary and disjoining pressures are obtained. Cavitation cannot occur as the film thickness is smaller than the critical cavitation radius, and the meniscus can exist in metastable state. A curve-fitted meniscus boundary condition is developed; a force function of the form F n = An −3 − Cn −2 can be applied at the boundaries of a liquid film to create curvature and form a meniscus.

Article

A new technique for the generation of negative pressure in liquids is described, based on the pressure difference that exists across a curved liquid-vapour interface. Menisci in pores having very small radii may induce large negative pressures, or tensions, within the liquid phase. The magnitude of this tension is readily controlled through the pressure of the external vapour phase. Liquid butane when contained in hollow capsules, or Bertholet tubes, with walls formed from Vycor porous glass (pore radius ca. 5 nm) has developed negative pressures as large as -4 MPa for brief periods and lesser tensions for much longer times. This tension approaches the theoretical limit (ca. -6 MPa) calculated from the Laplace equation. Maximum possible tensions based on the theory of homogenous nucleation and on spinodal decomposition are much larger and, in principle, may be reached by reducing the pore size. Our unsuccessful attempts to do so are described.Key words: Bertholet tube, liquid, negative pressure, nucleation.

A simple method for the generation of negative pressure in liquids

A new technique for the generation of negative pressure in liquids is described, based on the pressure difference that exists across a curved liquid-vapour interface. Menisci in pores having very small radii may induce large negative pressures, or tensions, within the liquid phase. The magnitude of this tension is readily controlled through the pressure of the external vapour phase. Liquid butane when contained in hollow capsules, or Bertholet tubes, with walls formed from Vycor porous glass (pore radius ca. 5 nm) has developed negative pressures as large as -4 MPa for brief periods and lesser tensions for much longer times. This tension approaches the theoretical limit (ca. -6 MPa) calculated from the Laplace equation. Maximum possible tensions based on the theory of homogenous nucleation and on spinodal decomposition are much larger and, in principle, may be reached by reducing the pore size. Our unsuccessful attempts to do so are described.

Cohesive Lift of Sap in the Rattan Vine

Cohesive Lift of Sap in the Rattan Vine

Negative Liquid Pressure at High Temperatures

IN my paper with Lieut. Entwistle on the effect of temperature on the hissing of water when flowing through a constricted tube (Proc. Royal Soc., A. 91, 1915) I have determined the temperature coefficient of an effect which indicates that the tensile strength of water would, be zero at a temperature between 279°C. and 363°C., with a mean from all the experiments published of 328°C. Sir Joseph Larmor's calculated result, 265°C., quoted by him in his letter in NATURE of June 29, agrees satisfactorily with the experimental value if we take into account the difficulty of getting the precise point at which hissing ceases, and that the result was obtained by extrapolation from observations taken at temperatures between 12°C. and 99°C. Lieut. Entwistle and I have experimented with other liquids—alcohol, benzene, acetone, and ether—and obtained results of a similar character. Experiments are now in abeyance, for my colleague is otherwise engaged.

Negative Liquid Pressure at High Temperatures

IT must have been remarked in the discussions of the various forms of equation of state for vapour-liquid (cf. K. Onnes and Keesom, “Ency. der Math., or in Leyden Communications, xi., 1912, p. 727) that this equation should determine the range of possible negative pressures in liquid. If we could assume the van der Waals form of equation to hold over the wide range that is concerned, it would readily follow that negative pressure could subsist only at absolute temperatures below 27 3/2 of the critical point of the substance. For water the latter is 365° C.; thus in that substance internal tension could (theoretically) persist up to 538° absolute, which is 265° C. Such an order of magnitude appears at first sight surprisingly high, though really there is nothing to compare it with. By an oversight I have recently (Proc. Lond. Math. Soc., 1916, p. 191) quoted the critical point of water as 365° absolute, and so obtained the much lower limit 35° C.; and it was a reference to experiments by Prof. H. H. Dixon (Proc. R. Dublin Soc., 1914, p. 233), realising, for vegetable sap, tensions of the order of a hundred atmospheresat temperatures around 80° C., that has given rise to this correction.