Equivalent fitting

Procedure Prepare a series of THI-DNPH Standard Solutions serially diluted from the Stock THI-DNPH Solution. Pipet 1, 2, and 5 mL, respectively, of the Stock THI-DNPH Solution, into separate 10-mL volumetric flasks, and dilute to volume with absolute, carbonyl-free methanol. Prepare a standard curve by injecting 5 p-L of the Stock THI-DNPH Solution, and the serially diluted THI-DNPH Standard Solutions into a 250-mm x 4-mm (id), 10-lm LiChrosorb RP-8 HPLC column (Alltech Associates, Inc., or equivalent) fitted with an ultraviolet detector set at 385 nm. The mobile phase is 50 50 (v/v) methanohO.l M phosphoric acid. Inject 5 pL of sample into the column. Adjustments in the mobile phase composition may be needed as column characteristics vary among manufacturers. At a mobile phase flow rate of 2 mL/ min and column dimensions of 250 x 4.6 mm, elute THI-DNPH at about 6.3 0.1 min. Measure the peak areas. Calculate the amount of THI in the sample from the standard curve. (For THI limits greater than 25 mg/kg, prepare a series of Standard THI-DNPH Solutions in a range encompassing the expected THI concentration in the sample.)... 

Apparatus Use a suitable atomic absorption spectrophotometer (Perkin-Elmer Model 3100 or equivalent) fitted with a graphite furnace (Perkin-Elmer HGA 600 or equivalent). Use a lead hollow-cathode lamp (Perkin-Elmer or equivalent) with argon as the carrier gas. Follow the manufacturers directions for setting the appropriate instmment parameters for lead determination. 

In a very thorough research study done at Southwest Research Institute (SWRI), San Antonio, TX, three sulfur test methods (D 2622, D 4294, and D 5453) were studied for fitness of use for the analysis of fuels at sulfur levels below 500 mg/kg [10]. All three were found to be equivalent for measurements in the 150-500 mg/kg range. But D 2622 and D 5453 were found to be of equivalent fitness for use down to 20 mg/kg, and D 5453 even to as low level as 1 mg/kg sulfur. It was also found that the latter method gives the best precision at such low sulfur levels. Later work in ASTM crosschecks confirms these conclusions. 

The final optimization experiment used a two-factor central conq)osite design with four repetitions at the center point. Each comer point was repeated twice giving a total of 16 runs. The concentration was varied between 0.18 M and 0.42 M and the amount of base used was between 1.075 and 1.925 equivalents. Fitting the data to a quadratic model showed only the concentration term and the square of the concentration term to be statistically significant. The yield was optimal when about 17 mL of water were used per gram of substrate. An approximately 140 fold scale up using the optimum concentration, 1.25 equivalents of sodium hydroxide at 45 C, and a 3 hour reaction time resulted in production of a 95.6% HPLC yield of the desired product. A total of 113 reactions was run over the course of this study. 

Unfortunately these were not the only problems. More remedial work was needed after the discovery of corrosion in the magnox reactors, and the equivalent fittings in the AGR had to be taken out and replaced with ones of a different material. This is perhaps one of the few faults which cannot be attributed directly to the builders. 

Figure 9-28. Roulette wheel selection. The size of each sector is equivalent to the fitness of the corresponding chro iTiosoiTie.

What is the binary equivalent of decimal 5 The largest power of 2 which fits 5 is 2 = 4. Therefore there is 1 x 2 in 5 with 1 left over 2 = 2 which is too big and so we write 0x21 finally we see that 1 x 2° = 1. The number 5 is made up from a 1 x 2 and a 1 X 2° = 1 but in binary we must not forget to put 0 x 2 in decimal we may write 304 meaning three hundred and four and if the 0 had been omitted then the number would have been thirty four (34). Thus, the binary equivalent of 5 is 101 and not 11. Other numbers may be converted into binary in an exactly similar fashion. Decimal 39 is ... 

It is equivalent, when an ftk spectrometer is used, to re-apodization of the data. Curve fitting is a method of modeling a real absorption band on the assumption that it consists of a series of overlapped peaks having a specific lineshape. Typically the user specifies the number of peaks to attempt to resolve and the type of lineshape. The program then varies the positions, sizes, and widths of the peaks to minimize the difference between the model and the spectmm. The largest difficulty is in knowing the correct number of peaks to resolve. Derivative spectra are often useful in determining the correct number (18,53,54). 

The flow resistance of pipe fittings (elbows, tees, etc) and valves is expressed in terms of either an equivalent length of straight pipe or velocity head loss (head loss = Kv /2g ). Most handbooks and manufacturers pubHcations dealing with fluid flow incorporate either tables of equivalent lengths for fittings and valves or K values for velocity head loss. Inasmuch as the velocity in the equipment is generally much lower than in the pipe, a pressure loss equal to at least one velocity head occurs when the fluid is accelerated to the pipe velocity. 

The viscous or frictional loss term in the mechanical energy balance for most cases is obtained experimentally. For many common fittings found in piping systems, such as expansions, contrac tions, elbows and valves, data are available to estimate the losses. Substitution into the energy balance then allows calculation of pressure drop. A common error is to assume that pressure drop and frictional losses are equivalent. Equation (6-16) shows that in addition to fric tional losses, other factors such as shaft work and velocity or elevation change influence pressure drop. 

Type of fitting or valve Additional friction loss, equivalent no. of velocity heads, K... 

A 3-I. three-necked, round-bottom flask is fitted with a mechanical stirrer through a mercury seal, a reflux condenser and a i-l. separatory funnel. A mixture of 200 g. (r mole) of 2,3-dibromopropene (Org. Syn. 5, 49) and 200 cc. of dry ether is added. The flask is now cooled in an ice bath, the stirrer is started, and one molecular equivalent of cyclohexylmagnesium bromide, prepared from 31 g. of magnesium, 204 g. of cyclohexyl bromide and 400 cc. of dry ether (Note i) is added at such a rate that the mixture refluxes gently (Note 2). The addition takes about one-half to three-quarters of an hour. Two layers are formed and magnesium bromide may or may not separate. 

Total equivalent length of pipe (assuming that every fitting has an average 5 m of equivalent pipe length, to account for friction) = 1000 + 25 X 5... 

Table A.2 Friction in fittings in equivalent of pipe length (ft)...

Figure 4 Sample spatial restraint m Modeller. A restraint on a given C -C , distance, d, is expressed as a conditional probability density function that depends on two other equivalent distances (d = 17.0 and d" = 23.5) p(dld, d"). The restraint (continuous line) is obtained by least-squares fitting a sum of two Gaussian functions to the histogram, which in turn is derived from many triple alignments of protein structures. In practice, more complicated restraints are used that depend on additional information such as similarity between the proteins, solvent accessibility, and distance from a gap m the alignment.

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