Dynamic kill

While a bottom-supported vessel must divert when shallow gas is encountered, a floating vessel has the additional option of simply abandoning the well. This option has led to the use of riserless systems when drilling the surface hole. However, a dynamic kill provides the only means of controlling the well. A dynamic kill makes use of annular friction as well as a heavier mud to hold backpressure on the formation. If very short wellbores are involved, the dynamic kill rates are usually to large to be practical. A well being drilled with a riserless system is very likely to be lost if shallow gas is encountered. 

A biological interpretation of this problem in terms of population dynamics could be as follows both prey animals A and predators B living on them are reproduced by division in a medium with a spontaneous production of food E for them. With these studies in mind the model has to be slightly modified any new predator B is bom after killing the prey animal A with the probability < 1, which needs in our statement of the problem just a trivial replacement of /zB(r) for /ttB(r). 

Kinase inhibitors represent a dynamic area of research for new cancer therapies. Traditional chemotherapeutic agents target general cellular processes, namely cell division. The drugs, while effective against cancer cells, also kill many healthy cells in the patient and cause severe side effects. In contrast, kinase inhibitors are much more narrowly focused and may often be tailored to affect specific members of a receptor family. Kinase inhibitors effectively treat the cancer while minimizing side effects for the patient. 

Bio/dynamics 1991), 30-47% and 53%, respectively, of pregnant females treated by gavage with 0.075 mg/kg/day for 145-204 days (intermediate duration) died (or were killed due to morbidity) in late gestation or during parturition dams exposed to 0.015 mg/kg/day for similar durations did not have an increased mortality rate (IRDC 1985). Compound-related deaths were not observed in male rats exposed to 0.075 mg/kg/day for similar durations (Bio/dynamics 1991 IRDC 1985). 

The main reason why numerical waves have not been discussed much in the CFD community is that most RANS codes use excessive artificial viscosity and large turbulent viscosity levels (due to turbulence models) which kills all numerical waves. They also kill all acoustic waves and all hydro-dynamic modes and cannot be used for the present needs of combustion research. Methods which can compute accurately waves in reacting flows must use centered schemes and LES (or DNS) formulations in order to avoid damping all waves (physical and numerical). A convenient way to illustrate this point is to compare the various viscosities pla3ung a role in a CFD code ... 

Use organically acceptable sprays and dusts with restraint. Some, especially botanical insecticides, present the same risks to the dynamic living community in your garden as do. synthetic poisons. Use them too freely, and you may face the problem known as pest resurgence. In other words, you kill off some pests and most of their predators, and the... 

The deadening chill of formalism is as fatal to good indexing of facts as it is to worship. The letter kills the spirit gives life. Dynamic subject heading lists are compiled, maintained, and administered with informed skill and care as potent instruments for better indexing and potent aids to skilled searchers. Static subject heading lists, compiled and administered under slavish adherence to a frozen set of rules, are road blocks. 

The UV radiation disinfects germs in an aqueous system, which can be operated as plug flow, continuous flow, or other modes. The killing efficiency is controlled by many factors, which can be classified into two aspects disinfection kinetics and flow dynamics. Like many other processes in both chemical and environmental engineering, the mathematical modeling of the UV disinfection can be started from simulation of distribution of flow velocity together with definition of suitable kinetic model(s). The disinfection effect in terms of survival of pathogens as a function of operational conditions such as time and dose can then be estimated. Since the mathematical models involve many unknown parameters that must be experimentally determined, they are mainly... 

On the other hand, community structure may change through indirect mechanisms. Indirect effects are those that are not due to toxic effects per se. For example, an insecticide may not be toxic to birds, but the birds may disappear because the insecticide kills off the insects on which it feeds. Conversely, the body size and population density of a species of minnow may increase in contaminated sites due to toxic effects on competing species (more food available for the minnow) or on predators such as bass. It has also been suggested that such changes in community structure come about because some species are more genetically plastic than others, and so are better able to adapt to novel stressors such as pollution. Thus, the more sensitive species would not be able to adapt to this stressor and become extinct locally. These types of perturbations in community structure and dynamics may ultimately compromise the stability, sustainability, and productivity of affected ecosystems. 

Figure 1. Prediction of the effect of herbicide rotation in the original model. A. Overall average effect of scenarios with different selection pressures (a = 0.1= 90% effective kill (EK) a = 0.01 = 99% EK, a = 0.33 = 75% EK, a = 0.5 = 50% EK), seed bank dynamics (n See Table III) and differential fitness. The different scales give the different rotational scenarios, from mono-herbicide to one treatment in 3 seasons. B. Calculated effect of herbicide stoppage, and restarting at various intervals. Source Redrawn from equations and figures in refs. (3) and (4).

Figure 4. Lack of enrichment for resistance under various selection pressures (a), under different rotation strategies, with different weed seed dynamics in the seed bank. The selection pressure is also shown as effective kill (the percent reduction in sensitive propagules over a whole season) with the assumption that the rare resistant individuals are totally unaffected by the herbicide. Here fon = 1 while f0/f takes a relatively large value (A) and a (B) value so small that / // has a negligible effect.

Figure 6. Amplification of resistance in a 3 year period as a function of fitness in the off years (fm = l) and seed bank dynamics. A 1 on 2 off rotational scheme is used and the on herbicide has a fixed selection pressure of a = 10 (effective kill = 90 %).

Ideally, one would like to measure the mass transfer rates and concentrations in each compartment of a tissue as a function of both time and space and develop precise mathematical models on the basis of these data. Such models could then be used to predict spatial and temporal concentrations of various agents in a variety of normal and neoplastic tissues. Since the selective tumor cell kill depends on the concentration-time history of a drug, such information could be used in developing optimal dose schedule of anticancer agents. However, there are several practical problems in carrying out such detailed measurements directly, and in developing such detailed, dynamic, predictive mathematical models. Nevertheless, it is possible to obtain considerable useful information about mass transfer in tumors, using the experimental and theoretical approaches discussed in the next two sections. 

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