Single common problems

Problems can arise if several cupboards, each with its own fan, are connected to a single common duct and discharge stack. If a fume cupboard was switched off or a fan failed, flow through the cupboard could be reversed causing contaminants to be discharged into the room. The collecting duct should be kept at a lower pressure by its own fan to reduce this risk. 

One of the common problems associated with underwater pelletizers is the tendency of the die holes to freeze off. This results in nonuniform polymer melt flow, increased pressure drop, and irregular extrudate shape. A detailed engineering analysis of pelletizers is performed which accounts for the complex interaction between the fluid mechanics and heat transfer processes in a single die hole. The pelletizer model is solved numerically to obtain velocity, temperature, and pressure profiles. Effect of operating conditions, and polymer rheology on die performance is evaluated and discussed. 

No single method is perfect and common problems include the difficulty of defining peak boundaries accurately, operator dependence on precision and the need for a finite time to make each measurement. A major disadvantage of manual measurements is the necessity that all peaks of Interest must be completely contained on the chart paper (or adjusted to remain on the chart paper by varying the detector attenuation during the... 

A common problem encountered in large chemical companies involves the distribution of a single product (30 manufactured at several plant locations. Generally, the product needs to be delivered to several customers located at various distances from each plant. It is, therefore, desirable to determine how much Y must be produced at each of m plants (Yv Y2,..., Ym) and how, for example, Ym should be allocated to each of n demand points (YmV Ym2,. Ymnl The cost-minimizing solution to this problem not only involves the transportation costs between each supply and demand point but also the production cost versus capacity curves for each plant. The individual plants probably vary with respect to their nominal production rate, and some plants may be more efficient than others, having been constructed at a later date. Both of these factors contribute to a unique functionality between production cost and production rate. Because of the particular distribution of transportation costs, it may be... 

A major problem in function prediction is the multidomain nature of many proteins, where a protein can be assigned die function of another, even though it may only share a single common domain. Such... 

It shonld not surprise us that quite distinct species nse some of the same molecules as pheromones. Remember that all extant life had a single common origin and that mnltiple biochemical pathways are shared by basically all living organisms. Thus, using mnch the same set of biochemical tools, multiple organisms have come to common solntions to common problems. This is one more example of the unity of life on Earth. 

A common problem experienced under the current automation paradigm, with the demand for greater results in shorter iteration cycles (1-2 weeks), is that screeners are required to collect data from several single assay workstations, often run on different software platforms. With the demand for results on more compounds per week, the screeners must process more samples through the assays, each with fewer data points and replicates. This trade off in quality for quantity can result in lower overall data fidelity. 

Environmental exposures are present through the human lifetime. However, they may vary considerably over time at the same location, for example, because of the local or global changes in emission and environmental pollution levels. Environmental exposures of humans consist of exposures outdoors and indoors as well as at workplaces these environments may significantly differ. The exposure media include air, water, and soil and dust. Historically, research on human exposures to chemicals and associated health effects has been conducted mostly on single chemicals. In addition, several studies have dealt with complex mixtures, such as diesel fuel and gasoline, by-products from coal combustion, and tobacco smoke. A common problem of complex mixtures is that the composition may vary from one exposure to another and, as a result, the associated toxicity may vary. For a better understanding... 

The roller bottle technique is a well-established and successful culture method widely used for the production of cells and products. One reason for this is that a single contamination event does not mean that the whole batch is lost, as with a single unit process. However, roller culture needs a considerable financial investment both in the apparatus itself and in incubator/hot-room facilities. Also, some cell lines (particularly epithehal) may not be as successfully grown in roller bottles as in stationary bottles. Common problems are streaking, clumping or inadequate spreading over the total surface (e.g. non-locomotory cell lines). An alternative scale-up route is to use multisurface stationary systems such as the Nunclon Cell Factory (Nunc) (see section 5.7) or the CellCube (Costar). 

Calculate the minimum value of a, a such that P(a,) and AOS(d,) have a single common point v by solving the LP problem below ... 

A common problem in macromolecular crystallization is inducing crystals to grow that have never previously been observed. The single major obstacle to obtaining any crystals at all is, however, ensuring the formation of stable nuclei of protein crystals. In cases where the immediate problem is growing crystals, attention must be thus directed to the nucleation problem, and any approach that can help promote nucleation should be considered. 

The problems we aim to solve are common problems for physical chemists, the computation of the value of a goal quantity by applying formulas. This is simple when there is a single formula to apply and the values of all other quantities in the formula are known, i.e. either specified by the user or available in the knowledge base. The process becomes complex when more than one formula is applicable and when the values of some of the quantities in the formulas are unknown. Unknown quantity values may be computed from other formulas. Then the formulas should be used in a correct sequence. 

A common problem in removal of vapors from air is the simultaneous adsorption of water vapor. The capacity of the carbon for organic vapors may be reduced by 50 to 70 percent if the relative humidity is 80 percent but there is little effect if the relative humidity is less than 30 percent. This may make it worthwhile to raise the temperature of the feed by 20 to 30°F, even though this decreases the equilibrium capacity for a single adsorbate. 

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