Feeding-fasting cycle

UNIT V Integration of Metabolism Chapter 23 Metabolic Effects of Insulin and Glucagon 305 Chapter 24 The Feed/Fast Cycle 319 Chapter 25 Diabetes Mellitus 335 Chapter 26 Obesity 347 Chapter 27 Nutrition 355 Chapter 28 Vitamins 371... 

In Chapter 16 the focus of the discussion is the integration of the major metabolic processes in mammals. The chapter begins with an overview of metabolic processes and a description of the metabolic contributions of several major organs. This is followed by a discussion of the feeding-fasting cycle, which illustrates several important control mechanisms. Chapter 16 ends with a brief review of the major mammalian hormones and their mechanisms of action. 

Multicellular organisms require sophisticated regulatory mechanisms to ensure that all their cells, tissues, and organs cooperate. For example, the feeding-fasting cycle illustrates how a variety of organs contribute to the acquisition of food molecules and their use. 

The thyroid status is teleosts also exhibits a feeding/fasting cycle (Fig. 8, panel C). However, although T3 levels are higher in fed trout than in fasted trout, there are contradictions in the literature on the appearance of feeding-associated rises in plasma T3 (Matty and Lone 1985) but a rapid increase in plasma T3 (< 3 h) has been identified in refed trout (Cook and Bales 1987). 

In this paper we will first describe a fast-response infrared reactor system which is capable of operating at high temperatures and pressures. We will discuss the reactor cell, the feed system which allows concentration step changes or cycling, and the modifications necessary for converting a commercial infrared spectrophotometer to a high-speed instrument. This modified infrared spectroscopic reactor system was then used to study the dynamics of CO adsorption and desorption over a Pt-alumina catalyst at 723 K (450°C). The measured step responses were analyzed using a transient model which accounts for the kinetics of CO adsorption and desorption, extra- and intrapellet diffusion resistances, surface accumulation of CO, and the dynamics of the infrared cell. Finally, we will briefly discuss some of the transient response (i.e., step and cycled) characteristics of the catalyst under reaction conditions (i.e.,... 

During periodic operation, the system is forced to follow changes in the input. So-called cycling of the feed is the case where oscillations are applied to the concentrations of the reactor feed. Whether the input is followed perfectly depends on the dynamic behavior of the system. The most important parameter describing the dynamic behavior is the characteristic response time A small value of corresponds to a fast-responding system. Based on the period of the forced oscillation and characteristic response time of the system three different periodic operations can be distinguished [27,45] ... 

The selection of adsorbents is critical for determining the overall separation performance of the above-described PSA processes for hydrogen purification. The separation of the impurities from hydrogen by the adsorbents used in these processes is generally based on their thermodynamic selectivities of adsorption over H2. Thus, the multicomponent adsorption equilibrium capacities and selectivities, the multi-component isosteric heats of adsorption, and the multicomponent equilibrium-controlled desorption characteristics of the feed gas impurities under the conditions of operation of the ad(de)sorption steps of the PSA processes are the key properties for the selection of the adsorbents. The adsorbents are generally chosen to have fast kinetics of adsorption. Nonetheless, the impact of improved mass transfer coefficients for adsorption cannot be ignored, especially for rapid PSA (RPSA) cycles. 

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