Push and pull mechanisms

The refresh functionality was supported both by push and pull mechanisms. The PLM system could trigger the refresh function to push changes to the SDM system. The SDM system is capable to puU changes from the PLM system. This was bound to a user interaction. The cross-domain communication can be initially supported by those basic building blocks. But this elementary approach leaves some potential for further improvement like... 

In the local mechanical fluctuation model, the local motions of the amino acids on the proximal side of the heme are coupled to the heme through the side group of the proximal histidine. The side chain of the proximal histidine is covalently bonded to the Fe. This bond is the only covalent bond of the heme to the rest of the protein. Thus, motions of the a-helix that contains the proximal histidine are directly coupled the Fe. These motions can push and pull the Fe out of the plane of the heme. Since the CO is bound to the Fe, these motions may induce changes in the CO vibrational transition frequency causing pure dephasing. 

Another mechanism is related to polymer viscoelastic behavior. The interfacial viscosity between polymer and oil is higher than that between oil and water. The shear stress is proportional to the interfacial viscosity. Because of polymer s viscoelastic properties, there is normal stress between oil and the polymer solution, in addition to shear stress. Thus, polymer exerts a larger pull force on oil droplets or oil films. Oil therefore can be pushed and pulled out of dead-end pores. Thus, residual oil saturation is decreased. This mechanism is detailed in Chapter 6. 

The ServoPro, an exclusive feature of the Utah Arm, is designed for amputees with shoulder disarticulation, interscapulothoracic, or brachial plexus injuries. The ServoPro eliminates the electrodes normally required to operate the Utah Arm. The system may be the only option, which can provide functional control of both elbow and hand. The ServoPro is based on a harness, but instead of cables, electronic components are pushed and pulled to generate command signals that will control the electrically powered prosthesis. The ServoPro requires much smaller excursion of movement and less effort compared with body-powered cables in equivalent mechanical systems. The servo control is accurate and it uses feedback from sensors in the elbow and hand. 

The concept of an apolar (hydrophobic)-polar (e.g., charge) repulsive free energy of hydration, AG,p, contributes to understanding the mechanism whereby ATPases function in three distinguishing respects. First and second, ATP binding, and particularly on hydrolysis with formation of ADP plus Pi, has the potential to effect both push and pull components of force. Third, release of Pi results in development of an elastic pull component of force that is most in evidence during isometric contractions. These three elements of force development are discussed immediately below. 

Another novelty is the abrasion resistant material composition option that confers much improve abrasion resistance and somewhat lower coefficient of friction. The mechanical drive tape will also transfer tension and compressive forces when used in non-linear directions. Contributing factors are not only the tape s axial stiffness, providing the push and pull, but also its torsional and edge-bend flexibility. 

In conventional extrusion the maximum pressure that can be applied without stick-slip is around 0.23 GPa and so this provides a "process dependent" restriction on extrusion rate and the maximum draw ratio available. In push-pull extrusion, forces up to the tensile fracture of the material can be applied so the true maximum draw ratio for the material at a given temperature can be obtained. The limit of temperature and draw ratio detected in these studies has been added to the extrudability map (Figure 6) showing the maximum regions of the temperature/draw ratio map that may be studied. Clearly the push-pull process greatly extends the range of the extrusion technique. A series of samples prepared at the same draw ratio and temperature, but with different combinations of push and pull, have the same modulus, i.e. mechanical properties are independent of the applied pressure. 

Swain and Eddy have queried the wide applicability of the S l and Sif2 mechanisms and favored a push-pull termolecular process for the reaction of pyridine with methyl bromide in benzene solution for example, they have suggested that the effects observed on the addition of methanol, phenol, p-nitrophenol, and mercuric bromide to the reaction mixture can be explained by an intermediate of type 168. ... 

The HIV-1 protease, like other retroviral proteases, is a homodimeric aspartyl protease (see Fig. 1). The active site is formed at the dimer interface, with the two aspartic acids located at the base of the active site. The enzymatic mechanism is thought to be a classic acid-base catalysis involving a water molecule and what is called a push-pull mechanism. The water molecule is thought to transfer a proton to the dyad of the carboxyl groups of the aspartic acids, and then a proton from the dyad is transferred to the peptide bond that is being cleaved. In this mechanism, a tetrahedral intermediate transiently exists, which is nonconvalent and which is mimicked in most of the currently used FDA approved inhibitors. 

The mechanical properties of a material describe how it responds to the application of either a force or a load. When this is compared to an area, it is called stress, another term for pressure. Three types of mechanical stress can affect a material tension (pulling), compression (pushing), and shear (tearing). Figure 15.27 shows the direction of the forces for these stresses. The mechanical tests consider each of these forces individually or in some combination. For example, tensile, compression, and shear tests only measure those individual forces. Flexural, impact, and hardness tests involve two or more forces simultaneously. 

This is an example of acid catalysis and the effect is to pull electrons away from the leaving group. Often both acid catalysis and nucleophilic attack are involved in enzyme-catalysed reactions in what are known as push-pull mechanisms. 

Earlier attempts to use the AFM for mechanically stretching chromatin fibers have run into a rather unexpected artifact. Long native chromatin fibers isolated from chicken erythrocytes, or fibers assembled in vitro from purified histones and relatively short, tandemly repeated DNA sequences were deposited on mica or glass surfaces and pulled with the AFM tip [69,70]. In such stretching experiments the scanning of the sample in the x- and y-direction used for imaging was disabled, and the cantilever-mounted tip was allowed to move only in the z-direction, i.e., upwards and downwards, away and towards the surface. When the AFM tip is pushed into the sample, it may attach to the sample by non-specific adsorption upon retraction it stretches the sample and force-extension curves are recorded (see Fig. lb for an explanation of a typical force curve). 

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