Forced expulsions

The three consecutive phases of emesis include nausea, retching, and vomiting. Nausea, the imminent need to vomit, is associated with gastric stasis. Retching is the labored movement of abdominal and thoracic muscles before vomiting. The final phase of emesis is vomiting, the forceful expulsion of gastric contents due to GI retroperistalsis. 

Figure 8.8 Temperature-sensitive hydrogel microcapsule for pulsed release of droplets, (a) Optical micrograph of a microcapsule with a shell comprised of a thermosensitive PNIPAm hydrogel containing aqueous droplets dispersed in oil. b—e) Optical micrograph time series showing the forced expulsion of the oil and water droplets contained within the microcapsule when the temperature is increased...

Vomiting A reflexive rapid and forceful oral expulsion of upper gastrointestinal contents due to powerful and sustained contractions in the abdominal and thoracic musculature. 

The cyclotrimer products are liberated in subsequent, consecutive substitution steps with new butadiene, which is an exothermic reaction (AH) for expulsion of all-t-CDT by three /ran.v-butadienes along 8b —> l b. This process, however, is endergonic by 7 kcal mol-1 (AG) after entropic costs are taken into account. Therefore, 7b and 8b (stabilized by donors) are indicated to be likely candidates for isolable intermediates of the catalytic process, while the active catalyst l b, the intermediate species 2b, in particular, and other species will not be present in a sufficient concentration, since they are either too reactive or thermodynamically too unfavorable, for experimental characterization. Overall, the cyclotrimerization process is driven by a strong thermodynamic force with an exothermicity of —44.6 kcal mol-1 (AH for the process without a catalyst) for the fusion of three trans-butadiene to afford the favorable all-t-CDT. 

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