Push-pull process

The distinction of these limiting cases certainly is a formal one and the real mechanism might be intermediate, e.g. resembling some type of push-pull process. However, the two mechanisms lead to quite different consequences in their rate... 

Internal document creation and storage on a network drive or paper folders In the case of paper documents, the shipment of the sample and document is simultaneous, or alternatively send as an email attachment (scanned or real electronic document) in the case of databases (ERP), as a push/pull process data can be fetched [pull method] or be initiated actively [push method]... 

H.-C. Ludwig, G. Fischer and H. Becker, A quantitative comparison of morphology and fibre orientation in push-pull processed and conventional injection-moulded parts, Composites Science and Technology, 53, 235-239 (1995). 

FIGURE 1-6 Push/Pull Processes for the L. L. Bean Supply Chain... 

FIGURE 1-7 Push/Pull Processes for Ethan Allen Supply Chain for Customized Furniture... 

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. 

A sample of powdered Alathon 7050 was prepared by precipitating a solution in xylene into methanol. The compacted billet was extruded at draw ratio 30 and at 90°C, conditions that are unattainable in conventional extrusion (6) (Table 5). This datum can be added to the extrudabi1ity map (Figure 6) and shows that using a powder is not as efficient at promoting the extrusion as the push-pull process. There is also some loss of properties in the povyder extrudate (Section 3). 

Developments. A variety of process modifications aimed at improving surface finish or weld line integrity have been described. They include gas assisted, co-injection, fusible core, multiple Hve feed, and push—pull injection mol ding (46,47). An important development includes computer-aided design (CAD) methods, wherein a proposed mold design is simulated by a computer and the melt flow through it is analy2ed (48). 

Push-pull hood A protecting hood around a process with the air supply on one side of the contaminant source and the extract on the other side. 

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. ... 

Fig. 2-46 Sequence of push-pull fatigue in unidirectional glass-fiber/TS polyester RPs by mi-crobuckling processes.

The processes of meiosis and mitosis involve many motile events, from the separation of the daughter chromosomes to the final act of cell separation at cytokinesis (Wadsworth, 1993). DNA replication itself may be considered as a motile event, because the polymerase complex moves along the linear DNA. One of the most obvious motile events is the separation of the chromosomes along the mitotic spindle at anaphase. Details of the structure and polarity of microtubules in the spindle apparatus in meiosis and mitosis are known through electron and light microscopy, but it is not yet clear whether the chromosomes are pushed, pulled or... 

Polymers and supermolecules modified using electron push-pull chro-mophores are also of particular interest for nonlinear optics (NLO) [10-15]. NLO material has attracted much interest over the past 20 years and has been widely applied in various field (telecommunications, optical data storage, information processing, microfabrication, etc.). Chemists have developed ways to introduce NLO chromophores into many type of polymers, such as Hnear polymers, cross-linked polymers, and branched polymers, and have demonstrated their performance in NLO appHcations. 

Pappalardo, R. R., Sanchez Marcos, E., Ruiz-Lopez, M. F., Rinaldi, D. and Rivail, J. L. Solvent effects on molecular geometries and isomerization processes A study of push-pull ethylenes in solution, JAm.Chem.Soc., 115 (1993), 3722-3730... 

Two-Step (Push-Pull, Ping-Pong) Mechanisms Two-step mechanisms are typical of chemical catalytic processes, as opposed to redox catalysis processes, that are discussed and exemplified in Section 6.2. The first step following the generation at the electrode of the active form of the catalyst, Q, is the formation of an adduct, C, with the substrate A (Scheme 2.11). C requires an additional electron transfer to regenerate the initial catalyst, P. There are then two main possibilities. One is when C is easier to reduce (or oxidize in oxidative processes) than P. The main route is then a homogeneous electron... 

One should expect the activation entropy (AS ) to C=C rotation in Case 1 push-pull ethylenes to be negative, since the increase in polarity in the transition state should increase the order in the solvated structure. The effect should increase with increasing difference in polarity between ground and transition states, and also with increasing solvent polarity. These expectations have been completely borne out by experiments (78,140,143), as Table 22 shows. Contrary to what is generally found for conformational processes (144), AS values -20 e.u. are frequently found for C=C rotation in push-pull systems. 

Heavy wall tubing plain, coloured, striped tubing fabrications for instrumentation automotive push-pull cables industrial and process hydraulics and other fluids. .. Piping liners for glass-lined reactors, stainless steel reactors, glass equipment and mixers... Membranes, filter media, filter bags, cartridges, microfiltration membranes, vents and adsorbent products. .. 

Proteins or antibodies (36 pg) were mixed with ampholine pH 3.5—9.5 (final concentration of 5%, Amersham Biosciences, distributed by GE Healthcare, Uppsala, Sweden), p7 markers (Bio-Rad, Hercules, CA), and hydroxypropyl methyl cellulose (final concentration of 0.2% HPMC, Sigma-Aldrich, St. Louis, MO). The final protein concentration was 0.3mg/mL. Figure 17 shows a schematic of the sample preparation. The mixture was mixed thoroughly and was introduced to the capillary (eCAP neutral-coated, 50 micron X 30 cm, Beckman, Fullerton, CA) by hydrodynamic injection. Injections were performed using 20 psi for 99 s. The solution was then separated under an electric field of 25 kV for 10 min. The focused protein was then pushed/pulled out of the capillary through a mobilization process using the cathodic mobilizer (Bio-Rad, Hercules, CA). 

Carbonyl ylides derived from nitrogen-substituted carbonyl moieties provided for the synthesis of very stable push-pull dipolar intermediates. Although these compounds are quite stable, they still have sufficient reactivity to engage in cycloaddition and related processes. Carbonyl ylides derived from amides have been trapped in intermolecular cycloadditions to give aminals (Scheme 4.34) (56). 

---