Concurrent controls definition

Finally, some thought must be given to the clear definition of what is meant by experimental unit and concurrent control. 

Since densification of the granules in the drums and disks is brought on by gravitational force, there is a definite upper limit on both the rate and the extent of compaction that is attainable. This is specially true in the case of fine solids. In general, compaction of the granules occurs concurrently with their growth, and it is seldom possible to exercise independent control over these two actions of the pelletizer. 

Wheat bran has been the fiber source most commonly used to study effects of dietary fiber on calcium absorption in controlled laboratory studies. However, wheat bran and other forms of fiber as they occur in food products present several disadvantages in terms of definition and by concurrently altering intakes of other substances or materials known or suspected of having an adverse effect on the bioavailability of calcium such as phytates and oxalates (5,13,17,22-28). Several studies have been conducted which have sought to separate or compare the effects of phytate and fiber... 

Coppin CM, Gospodarowicz MK, James K, et al. Improved local control of invasive bladder cancer by concurrent cisplatin and preoperative or definitive radiation. The National Cancer Institute of Canada Clinical Trials Group. J Clin Oncol 1996 14(ll) 2901-2907. 

Although this is an area in which research is burgeoning, definite evidence of the effectiveness of EFAs in the treatment of mental disorders is lacking. There are some controlled trials of varying methodological quality in adult patients with schizophrenia, and unipolar and bipolar depression, with conflicting results (Fenton et ah, 2000 Maidment, 2000). The most encouraging trial is a preliminary study of 30 patients with bipolar disorder. It found that EFAs concurrent with mood stabilizers reduced the rate of recurrence of episodes (Stoll et al., 1999). 

One female and one male patient had hyperparathyroidism with elevated serum alkaline phosphatase activities and extensive bone changes characteristic of generalized osteitis fibrosa cystica. In both instances, the serum acid phosphatase activity of the serum fell to normal values after removal of the parathyroid adenoma despite transitorily increased serum alkaline phosphatase activity. The fifth patient was a female with osteopetrosis involving the major part of the skeleton. The serum acid phosphatase was 8.7 K.A. units, the highest in the control series— yet the serum alkaline phosphatase was within normal limits. It would appear, therefore, that some patients with skeletal disease may have a slight but definitely elevated serum acid phosphatase activity, at least as determined by the Gutman method (GIO, G14), which cannot be explained by concurrent prostatic carcinoma or by a spillover of alkaline phosphatase activity to a pH of 5.0. 

Many employers and manufacturers in the United States will use both approaches concurrently. The latter emphasizes a comprehensive analysis of hazards and a clear definition of which controls should be in place. Prescriptive standards and regulations may not always cover the unique situations of specific employers, manufacturers, and processes. 

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