Bare tension

In membranes with fixed lipid area, but variable number of lipids, the bare tension Fq is simply proportional the lipid chemical potential. For membranes with fixed number of lipids and variable lipid area, the physical meaning of Fq is less clear, but it can still be defined as a field that is conjugate to A in a Lagrange multiplier sense. This term also gives rise to a <7 term in the undulation spectrum, with the fluctuation tension Ftiuc = Fq + [36]. 

At leading (quadratic) order in h, the three tension-like quantities, Tframe. Uuo and Fq, thus have identical values. Nevertheless, they might differ from each other due to nonlinear corrections [90, 164—167]. For instance, the bare tension Fq is expected to deviate from the frame tension Fframe due to the effect of fluctuations. The exact value of the correction depends on the ensemble and differs for systems with a fluctuating number of lipids (variable number of undulating modes) or a fixed number of lipids (fixed number of modes). The former case was analyzed by Cai et al. [165] and the latter case by Farago and Pincus [168] and subsequently by a number of other authors [169-171]. Interestingly, the correction has an additive component in both cases. Hence a stress-free membrane has a finite bare tension. 

Spandex Fibers. Spandex fibers are suppHed for processing into fabrics in four basic forms as outlined in Table 3. Bare yams are suppHed by the manufacturer on tubes or beams and can be processed on conventional textile equipment with the aid of special feed and tension devices. In covered yams, the spandex fibers are covered with one or two layers of an inelastic filament or staple yam the hard yam provides strength and rigidity at full extension, which faciUtates knitting and weaving. 

It has been demonstrated that steel strength decreases rapidly with temperature increases above 260 °C (500 °F). At 538 °C (1000 °F), its strength both in tension and compression is approximately half, at 649 °C (1200 °F) its strength decreases to less than one quarter. Bare steel exposed to hydrocarbon fires may absorb heat at rates from 10,000 to 30,000 Btu/hr/sq. ft., depending on the configuration of the exposure. Due to the high heat conduction properties of steel, it is readily possible for normally loaded steel members or vessels to lose their strength to the point of failure within ten minutes or less of a hydrocarbon fire exposure. 

Mercury forms alloys, called amalgams, with other metals such as gold, silver, zinc, and cadmium. It is not soluble in water, but will dissolve in nitric acid. It has a high electric conductivity, making it useful in the electronics industry. However, unlike most other metals, it is a poor conductor of heat. Because of its high surface tension, it does not wet the surfaces that it touches. This characteristic also accounts for its breakup into tiny droplets when poured over a surface. If spilled, it should not be collected with bare hands, but with a thin piece of cardboard to scoop it up. 

Steel, aluminum, concrete, and other materials that form part of a process or building frame are subject to structural failure when exposed to fire. Bare metal elements are particularly susceptible to damage. A structural member undergoes any combination of three basic types of stress compression, tension, and shear. The time to failure of the structural member will depend on the amount and type of heat flux (i.e., radiation, convection, or conduction), and the nature of the exposure (one-sided flame impingement, flame immersion, etc.). Cooling effects from suppression systems and effects of passive fire protection will reduce the impact. 

If the interfacial tension of the bare solid surface is higher than that of the solid-liquid interface (7s > Isl), the right hand side of Young s equation is positive. Then cos has to be positive and the contact angle is smaller than 90° the liquid partially wets the solid. If the solid-liquid... 

We measure n versus P, solve the integral, and get the difference between the surface tension of the bare solid surface and that of the surface-vapor interface 7s — 7sv-... 

The bare wire is unwound, sometimes by a controlled tension device, and is preheated to a temperature above the Tg or Tm of the polymer to be extruded this is done so that the layer next to the bare wire adheres to it, and to drive moisture or oils off the conductor surface. The wire is fed in the back of the cross-heat die and into a guider tube. Upon exiting the guider, it meets the molten plastic, which covers it circumferentially. Since the wire speed, which is controlled by a capstan at the end of the line, is usually higher than the average melt velocity, a certain amount of drawdown is imposed on the melt anywhere from a value slightly greater than unity to 4. 

If the air in the tube is evacuated, leaving only the vapour of the liquid, there is usually a slight, barely measurable, increase in the surface tension.4... 

It is a matter of course that the different surfactant coverages are also reflected in the corresponding surface tensions y of the latexes (see Fig. 4b). An increase of the surface tension with increasing diameter is observed. The miniemulsions based on polystyrene particles exceeding 100 nm have a surface tension of close to the one of pure water (72 mN nr1)- This is due to the fact that the bare particle surface is so large that adsorption equilibrium ensures a very low surfactant solution concentration. Smaller particles with their higher sur-... 

A limit of adsorption experiments is that only changes of the surface tension upon adsorption of a substance can be measured. In many practical applications this is not a severe limitation because Ksv- One example is alumina. For y-AbO. McHale et al. measured a value of 1.67 J/m for ys - ysv [871- This is close to the surface tension of bare K-AI2O3, so that 1.67 J/m % ys-... 

Ms and Msl are the internal surface energies per unit area for the bare and the immersed surface, respectively. Hence from measuring the heat of immersion one can obtain information about the internal surface energy, but it is not possible to measure the surface tension directly. 

A similar smface tension treatment can be made for the interface between metal oxides and metals. Native oxides typically have lower surface free energies than the bare metal, in turn driving the surface oxidation of most metals. However it is not true that all oxides have lower surface tensions than all metals or semiconductors. For the case of growth of a metal oxide film on a dissimilar metal, or a metal on a supporting metal oxide substrate, the initial phases of growth are determined by the respective surface tensions. These are described by the Young-Dupre equation... 

From the computations of Robert von Helmholtz, the temperature of the triple point for water would barely exceed the temperature of fusion under atmospheric pressure it would be +0 .0076 C. the tension of saturated water vapor above the liquid would surpass that above ice by 0.000332 mm. on account of their smallness these numbers escape any exact experimental verification. 

For a soil that is barely saline (EC 4 mS/cm), an osmotic pressure of about 1.5 atmospheres would result. In other words, the water in this moist soil would not be freely available to plant roots, but would be retained in a lowered free energy state equivalent to 1.5 atmospheres of water tension. This, however, is insufficient tension to seriously impede water uptake by plants. More important effects of soil salinity are likely to include particular ion toxicity effects (e.g., Na, Cl ) and nutritional imbalances (e.g., excessive Na" or uptake relative to Ca " and Mg ). 

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