Variable-Influence Pathways

Whenever the procedure construct-variable-influence-pathways has to generate a number of alternative variable-influence paths, it employs a breadth-first search strategy. The procedure, expand-node, is used to establish the expansion list through the following algorithm ... 

The procedure construct-variable-influence-pathways applies to each node of the variable-influence pathway the procedure, classify-branch, which in turn classifies each branch of the pathway according to the type of the technology, which can be used to control the variable-value specifying the node. The algorithm of this procedure is given below ... 

The procedure identify-nondissipative-pathways constructs the set of enabling conditions that lead to a top-level event. It takes as its input the variable-influence pathways, which it obtains from the procedure, construct-variable-influence-pathways. TLE variables are then identified, and each variable contained in the set is traced to identify potentially feasible roots for causing the TLE. When an achievable root is identified (i.e., an input disturbance, controlled or uncontrolled, which can enable the top-level event), it is collected into root causes and returned. The algorithm used by this procedure is shown below ... 

There is great interest in the mechanisms of cell death since better understanding might lead to therapy that slows the rate of aging and prevents or treats human disease. Two major processes of cell death have been described, apoptosis and neaosis other alternative pathways generally are variations of these (Formigli et al, 2000 Sperandio et al, 2000 Reed, 1999). Some of the intracellular events related to these types of death have been discovered (Reed, 2000). After exposure to noxious stimuli, the balance between antiapoptotic and proapoptotic influences can result in either survival or death. Many of these variable influences and the subsequent downstream concatenated events involve oxidation, which targets cellular components such as DNA, cellular proteins and membrane phospholipids. Our laboratory and others have studied the role of the redox-active cellular constituents nitric oxide ( NO) and membrane phospholipid... 

These variables influence the reaction pathway and product distribution [59]. 

SnCU is also the principal source for alkyltin chlorides, RnSnCU-n- Allyltrialkyltin reagents react with SnCU to produce allyltrichlorotin species through an Se2 pathway (eq 1). Silyl enol ethers react with SnCU to give a-trichlorotin ketones (eq 2). Transmetalation or metathesis reactions of this type are competing pathways to nucleophilic addition reactions where SnCU is present as an external Lewis acid. As a consequence, four important experimental variables must be considered when using SnCU as a promoter (1) the stoichiometry between the substrate and the Lewis acid (2) the reaction temperatnre (3) the nature of the Lewis base site(s) in the substrate and (4) the order of addition. These variables influence the reaction pathway and product distribution. ... 

The smooth muscle cell does not respond in an all-or-none manner, but instead its contractile state is a variable compromise between diverse regulatory influences. While a vertebrate skeletal muscle fiber is at complete rest unless activated by a motor nerve, regulation of the contractile activity of a smooth muscle cell is more complex. First, the smooth muscle cell typically receives input from many different kinds of nerve fibers. The various cell membrane receptors in turn activate different intracellular signal-transduction pathways which may affect (a) membrane channels, and hence, electrical activity (b) calcium storage or release or (c) the proteins of the contractile machinery. While each have their own biochemically specific ways, the actual mechanisms are for the most part known only in outline. 

Thus, the parameters of acoustic intensity, temperature, ambient gas, and solvent choice have strong influences on sonochemical reactions. It is clear that one can fine tune the energetics of cavitation by the use of these variables and hence exercise control on the rates and reaction pathways followed by the associated chemistry. Specific examples will be discussed shortly. Clearly, the thermal conductivity of the ambient gas (e.g., a variable He/Ar atmosphere) and the overall solvent vapor pressure provides easy mechanisms for experimental control of the peak temperatures generated during the cavitational collapse. 

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