Chain of events

The first case study shows how a knowledge of steel microstructures can help us trace the chain of events that led to a damaging engineering failure. 

Provides a chain of events or considerations that is based on the site-specific conditions involved. 

The purpose of a hazard tree is to identify potential hazards, define the conditions necessary for each hazard, and identify the source for each condition. Thus, a chain of events can be established that forms a necessary series of required steps that results in the identified hazard. This is called a hazard tree. If any of the events leading to the hazard can be eliminated with absolute certainty, the hazard itself can be avoided. 

It is therefore useful to distinguish between active and latent errors or failures. An active human error has an immediate effect in that it either directly causes a hazardous state of the system or is the direct initiator of a chain of events which rapidly leads to the imdesirable state. 

Because errors are frequently recoverable, it is also appropriate to define another category of errors, recovery failures. These are failures to recover a chain of events leading to a negative consequence (assuming that such a recovery was feasible) before the consequence occurs. This includes recovery from both active and latent failures. 

However, in the case of a root cause analysis system, a much more comprehensive evaluation of the structure of the accident is required. This is necessary to unravel the often complex chain of events and contributing causes that led to the accident occurring. A number of techniques are available to describe complex accidents. Some of these, such as STEP (Sequential Timed Event Plotting) involve the use of charting methods to track the ways in which process and human events combine to give rise to accidents. CCPS (1992d) describes many of these techniques. A case study involving a hydrocarbon leak is used to illustrate the STEP technique in Chapter 7 of this book. The STEP method and related techniques will be described in Section 6.8.3. 

These possible sources of problems in a molded part should be marked on the product drawing and explained to the mold designer for corrective action or creating an awareness of possible product defects. This is a necessary step in the chain of events in which the aim is to produce a tool that will provide useful products. Even if the mold s design, workmanship, and operation are carried out to the highest degree of quality, they cannot overcome a built-in weakness due to the product design. 

The legalistic notion that only validated processes are to be used assumes that the chain of events from raw materials to analysis of the final material can be validated in globo, something that is patently impossible with the given number of adjustable parameters, not to mention unforeseen glitches. Doing the validations in bits and pieces (modules process, sampling, analysis, data evaluation, etc.) certainly helps, but does not cover the... 

Figure 49-9. Possible chain of events leading to opening of the Ca release channel. As indicated in the text, the Ca voltage channel and the Ca release channel have been shown to interact with each other in vitro via specific regions in their polypeptide chains. (DHPR, dihydropyridine receptor RYR1, ryanodine receptor 1.)...

Risk analysis. The risk of accidents can be assessed in terms of two factors severity and probability of the accident. Severity is high if consequences of the accident to employees, the public, the environment, and the plant are significant. Severity is related to the amount and properties of hazardous (toxic, flammable, explosive) substances that can escape to the surroundings during the accident, and to the energy that is released during the accident. Probability is associated with the likelihood of the occurrence of unwanted chains of events and the time of development of undesired events starting from the disturbance. If the time... 

At the present time it is difficult to single out any one factor that could be held ultimately responsible for cell death after cerebral ischaemia. Recent studies, however, have provided us with sufficient evidence to conclude that free radical damage is at least one component in a chain of events that leads to cell death in ischaemia/reperfiision injury. As noted earlier in this review, much of the evidence for free radicals in the brain and the sources of free radicals come from studies in animals subjected to cerebral ischaemia. Perhaps the best evidence for a role for free radicals or reactive oxygen species in cerebral ischaemia is derived from studies that demonstrate protective effects of antioxidants. Antioxidants and inhibitors of lipid peroxidation have been shown to have profound protective effects in models of cerebral ischaemia. Details of some of these studies will be mentioned later. Several reviews have been written on the role of oxygen radicals in cerebral ischaemia (Braughler and HaU, 1989 Hall and Btaughler, 1989 Kontos, 1989 Floyd, 1990 Nelson ef /., 1992 Panetta and Clemens, 1993). 

During ischaemia, NOS is activated by calcium influx or by cytokines like tumour necrosis factor (TNF) or by lipopolysaccharide (LPS) and NO is produced in excess. It has been proposed that the excitotoxic effect of glutamate, which contributes to ischaemia-induced neuronal damage, is mediated by increased production of NO via a chain of events that includes increases in intracellular calcium (via glutamate activation of NMDA receptors), calcium activation of NOS, production of NO and peroxynitrite, and induction of lipid peroxidation. In fact, N-nitro-L-atginine, a selective inhibitor of NOS, has been shown to prevent glutamate-induced neurotoxicity in cortical cell cultures (Dawson rf /., 1991). 

Many measurements in pharmacology rely on a chain of events following receptor activation to produce a measurable response — for example, contraction of the smooth muscle of a piece of guinea-pig ileum in response to muscarinic receptor activation by acetylcholine. This means that the relationship between receptor occupancy and response is likely to be complex, and mechanisms of drug action in such systems are often difficult to define. 

A chain of events in which each link was precision-made. Should international society be any more lenient with men who had exploited the economies of whole countries, aiding and abetting the suffering of millions of people, than any local community was toward the robber who held up the owner of the comer store, took his money, and killed him in the course of the robbery It was, I thought, one element of a very persuasive theory. 

Recommendations which will break the chain of events (layers 1,2 ... 

The third-layer recommendations shown in Figure 12-1 emphasize the importance of management systems for preventing accidents. Management systems are designed to continuously, and on a long-term basis, either prevent the accident or eliminate the hazardous conditions, that is, to break the link in the chain of events that led to the accident. Examples may be (1) a quar-... 

Relapse does not just suddenly happen without warning or without reason. Research into the processes of relapse has identified a rather predictable chain of events that lead up to it (see Figure 7.1). Moreover, the fact that a client slips into old behavior once does not mean all is lost. On the contrary, a slip offers a tremendous opportunity for both client and therapist or counselor to improve upon the recovery plan. A slip identifies a weakness in the recovery plan and offers an indication of how to improve it. Remembering the transtheoretical stages of change model (see Chapter 3), a relapse is viewed as part of the change cycle and as a fairly common occurrence when a person learns how to overcome a drug problem. So there is no need to panic if a relapse occurs. 

Relapse roadmaps also can be used to increase awareness about apparendy irrelevant decisions. Using the roadmap, you can walk the client down the path she or he has planned for her- or himself so that the long-term consequences of choosing this path become illuminated. The client may not be aware of how the first turn on the map is risky, but when you start asking the client about each subsequent decision about where she or he goes next, then the risk of the chosen path may become more apparent. The relapse roadmap can be quite a useful method for understanding both past and future relapse chains of events. 

Relapse rehearsal is a way to plan ahead for how your client will successfully negotiate a lapse or relapse, should one occur. The goal is to circumvent the duration and severity of the lapse or relapse event by practicing for how to respond to such an event ahead of time. In addition, the relapse rehearsal can include a plan for circumventing the relapse chain of events before a client slips. The relapse rehearsal also can reduce the risk of a poor coping response, or even a slip or relapse should the chain progress that far. The goal is to develop a stay-safe plan for the client before he or she is even at risk, in hopes that the plan can be implemented quickly if needed when the risk arises. 

A strategy that can be used to renew commitment to the posttreatment recovery plan is called the decision matrix. The decision matrix is quite similar to a prosand-cons list used when a client or potential client is in the contemplation stage of change to enhance motivation. This strategy is particularly useful to challenge the rise of positive expectancies during a chain of events that place the client at risk for a lapse. 

When the relapse event has ended, then do a decon-tnere IS no progress. struction of the relapse chain of events so as to understand... 

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