Welch procedure

Allylic esters of fluoroacetic acid were used in the Ireland silyl ketene acetal rearrangement procedures by the Welch group at Albany [164]. For example, Eq. (53) shows a highly diastereoselective rearrangement which formed an early stage in syntheses of 2,3-dideoxy-2-fluoro-3-C-methyl pentose nucleosides [165, 166]. If a stereoselective synthesis of a functionalised monofluorocompound is... 

Tai SS-C, Welch MJ (2005) Development and evaluation of a reference measurement procedure for the determination of estradiol-17b in human serum using ID-LC/MS/MS. Anal Chem 77 6359-6363... 

Yap, W. T., Schaffer, R., Hertz, H. S., White, E. V., and Welch, M. J. (1983). On the difference between using linear and non-linear models in bracketing procedures in isotope dilution mass spectrometry. Biochem. Mass Spectrom. 10, 262-264. 

Gaggeler, H.W. Fast Chemical Separation Procedures for Transactinides . In Proceedings of The Robert A. Welch Foundation 41st Conference on Chemical Research. The Transactinide Elements , Houston, Texas, 27-28 October 1997, pp. 43-63. 

Welch et al. evaluated analytical procedures and environmental issues. They investigated methods for the extraction and detection of cocaine, some of its metabolites, morphine, and codeine from hair. They concluded from a round-robin study that extractions with 0.1 ATHCL are as efficient to remove the target compounds from hair as enzymatic digestion that dissolve the hair. GC/MS with either El or Cl provides accurate determinations of the targeted compounds. External contamination by powdered or vapor-deposited cocaine was incompletely removed by all approaches tested, making it difficult to differentiate incorporated drug from external contamination. This was also proved in extensive laboratory experiments by Wang and Cone. ... 

It is generally admitted that these procedures are efficient and eliminate the majority of drugs fixed to the external surface of hair. Cone et al. and Welch et al. have shown that when the hair is very contaminated, washing procedures eliminate only a portion of the drugs retained (see Chapter 2 for further information on this problem). The washing procedure that we have retained is the following a tuft of hair (about 200 to 500 mg) is rapidly rinsed by percolation with 10 mL of MeOH, 10 mL HCl 0.1 M, 10 mL HjO, and, lastly, 10 mL of MeOH. The hair is then dried. 

We have applied the same procedure that we developed for opiates. Morrison and colleagues used the same method presented recently by Welch et al. ... 

Finally, libraries aimed to chiral resolution of racemates will be covered here in particular, the use of chiral stationary phases (CSPs) has recently been reported for the identification of materials to be used for chiral separation of racemates by HPLC. The group of Frechet reported the selection of two macroporous poly methacrylate-supported 4-aryl-1,4-dihydropyrimidines (DHPs) as CSPs for the separation of amino acid, anti-inflammatory drugs, and DHP racemates from an 140-member discrete DHP library (214,215) as well as a deconvolutive approach for the identification of the best selector phase from a 36-member pool library of macroporous polymethacrylate-grafted amino acid anilides (216,217). Welch and co-workers (218,219) reported the selection of the best CSP for the separation of a racemic amino acid amide from a 50-member discrete dipeptide iV-3,5-dinitrobenzoyl amide hbrary and the follow-up, focused 71-member library (220). Wang and Li (221) reported the synthesis and the Circular Dichroism- (CD) based screening of a 16-member library of CSPs for the HPLC resolution of a leucine ester. Welch et al. recentiy reviewed the field of combinatorial libraries for the discovery of novel CSPs (222). Dyer et al. (223) reported an automated synthetic and screening procedure based on Differential Scanning Calorimetry (DSC) for the selection of chiral diastereomeric salts to resolve racemic mixtures by crystallization. Clark Still rejxrrted another example which is discussed in detail in Section 9.5.4. 

Therefore, various approaches for computing adjusted p values have been applied. These include permutation-adjusted p values, such as MaxT [55], which uses a two-sample Welch /-statistic (unequal variances) with step-down resampling procedures. Typically these adjustedp values are computed with an order of 10,000 permutations, which is computationally intensive. Although these methods are effective with large numbers of replicates, unfortunately this approach is not effective when datasets have small numbers of samples per group [56],... 

FNAB in the abdomen with both US and CT guidance has been described as safe and technically successful procedure by several authors (Ferrucci et al. 1980 Memel et al. 1996 Smith 1991 Welch et al. 1989). CT-guided FNAB of liver lesions has been reported to have sensitivity rates of 92% and specificity rates of 96% (Tuning et al. 1984). 

Welch TJ etal. (1989) CT-guided biopsy prospective analysis of 1,000 procedures. Radiology 171 493-496... 

Meanwhile there were many unsuccessful attempts to isolate the intrinsic factor, which is heat-labile and readily inactivated by chemical procedures (see reviews by Ungley, 1951-52 Welch and Heinle, 1951 Welch and Nichol, 1952 Castle, 1953 E. L. Smith, 1954 SchiUing, 1954). 

A particularly repellent reason for dismissal of personnel was instituted several decades ago during the brief tenure of one of the automotive "Big Three" CEOs, described as similar to one used by Jack Welch at GE. It consisted of mandatory classification of salaried employees into A, B, and C categories, in predetermined percentages, in the course of their regular performance evaluations. C category personnel would be denied bonuses, and if they remained a C after a second review, terminated. Never mind whether one or more of these groups of employees had been previously selected with care to include only top-level performers—off with their heads This procedure... 

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