Strip Values

The three most common ways to calculate a strip s value are to use 

The first method equates a strip s value with its spread to a bond having the same maturity. The main drawback of this rough-and-ready approach is that it compares two instruments with different risk profiles. This is particularly true for longer maturities. The second method, which aligns strip and coupon-bond yields on the basis of modified duration, is more accurate. The most common approach, however, is the third. This requires constructing a theoretical zero-coupon curve in the manner described previously in connection with the relationship between coupon and zero-coupon yields. 

When the bond yield curve is flat, the spot curve is too. When the yield curve is inverted, the theoretical zero-coupon curve must lie below it. This is because the rates discounting coupon bonds earlier cash flows are higher than the rate discounting their final payments at redemption. In addition, the spread between zero-coupon and bond yields should decrease with maturity. 

When the yield curve is positive, the theoretical zero-coupon curve lies above the coupon curve. Moreover, the steeper the coupon curve, the steeper the zero-coupon curve. 

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Figure 11.8.1 Principle of anodic stripping. Values shown are typical ones used potentials and Fp are typical of Cu analysis, (a) Preelectrolysis at 5 stirred solution, (b) Rest period stirrer off. (c) Anodic scan (v = 10-100 mV/s). [Adapted from E. Barendrecht, Electroanal Chem., 2, 53 (1967), by courtesy of Marcel Dekker, Inc.]...

Figure 5. FD ion velocity distributions shown in Cartesian coordinates in the center of mass system for barycentric energies (a) 0.21 eV, (b) 0.39 eV, and (c) 0.91 eV. "+), system s velocity of the center of mass (X), most probable velocity of the ideal spectator stripping product at 0°. (0), most probable values of Q = —0.20, —0.26, —0.55 for (a), (b), and (c), repsectively (Q), the spectator stripping values of Q —0.12, —0.21, —0.50 for (a), (b), and (c), respectively. The single contour lines to the right of each product distribution correspond to the 50% intensity profile of the primary ion beam.

Figure I. Relaxation effects of ethanol crude extract isolatedfrom Korea red ginseng, total ginsenosides, partially purified fraction 3 (F3), and Rgj on phenylephrine-precontracted rabbit corpus cavemosum strips. Values are means dS.E.M. from 7-9 experiments.

Finally, other tests to control jet fuel corrosivity towards certain metals (copper and silver) are used in aviation. The corrosion test known as the copper strip (NF M 07-015) is conducted by immersion in a thermostatic bath at 100°C, under 7 bar pressure for two hours. The coloration should not exceed level 1 (light yellow) on a scale of reference. There is also the silver strip corrosion test (IP 227) required by British specifications (e.g., Rolls Royce) in conjunction with the use of special materials. The value obtained should be less than 1 after immersion at 50°C for four hours. 

Anodic-stripping voltaimnetry (ASV) is used for the analysis of cations in solution, particularly to detemiine trace heavy metals. It involves pre-concentrating the metals at the electrode surface by reducmg the dissolved metal species in the sample to the zero oxidation state, where they tend to fomi amalgams with Hg. Subsequently, the potential is swept anodically resulting in the dissolution of tire metal species back into solution at their respective fomial potential values. The detemiination step often utilizes a square-wave scan (SWASV), since it increases the rapidity of tlie analysis, avoiding interference from oxygen in solution, and improves the sensitivity. This teclmique has been shown to enable the simultaneous detemiination of four to six trace metals at concentrations down to fractional parts per billion and has found widespread use in seawater analysis. 

Note. The period of 5-8 hours recommended above for attaining an equilibrium between the vapour molecules of the mixed solvent and those absorbed by the paper strip is essential if accurate R values are required for identification of mixed amino-acids. To illustrate the separation, as in the above experiment, this period may be reduced to about 2 hours. 

The extract is vacuum-distilled ia the solvent recovery column, which is operated at low bottom temperatures to minimise the formation of polymer and dimer and is designed to provide acryUc acid-free overheads for recycle as the extraction solvent. A small aqueous phase in the overheads is mixed with the raffinate from the extraction step. This aqueous material is stripped before disposal both to recover extraction solvent values and minimise waste organic disposal loads. 

The bottoms from the solvent recovery (or a2eotropic dehydration column) are fed to the foremns column where acetic acid, some acryflc acid, and final traces of water are removed overhead. The overhead mixture is sent to an acetic acid purification column where a technical grade of acetic acid suitable for ester manufacture is recovered as a by-product. The bottoms from the acetic acid recovery column are recycled to the reflux to the foremns column. The bottoms from the foremns column are fed to the product column where the glacial acryflc acid of commerce is taken overhead. Bottoms from the product column are stripped to recover acryflc acid values and the high boilers are burned. The principal losses of acryflc acid in this process are to the aqueous raffinate and to the aqueous layer from the dehydration column and to dimeri2ation of acryflc acid to 3-acryloxypropionic acid. If necessary, the product column bottoms stripper may include provision for a short-contact-time cracker to crack this dimer back to acryflc acid (60). 

The wet ester is distilled in the dehydration column using high reflux to remove a water phase overhead. The dried bottoms are distilled in the product column to provide high purity acrylate. The bottoms from the product column are stripped to recover values and the final residue incinerated. Alternatively, the bottoms maybe recycled to the ester reactor or to the bleed stripper. 

Seam thicknesses and depths vary tremendously. The most favorable deposits have shallow overburdens and thick seams that cover large areas. Acceptable stripping ratios, ie, overburden thickness to coal thickness, depend on the quaHty of the fuel. Ratios up to 10 1 have been used for bituminous coals, but lower ones are required for lignitic coals because of the lower heating value per unit weight. 

Specifications for the principal LPG products are summarized in Table 4. Detailed specifications and test methods for LPG are pubHshed by the Gas Processor s Association (GPA) (3) and ASTM (4). The ASTM specification for special-duty propane and GPA specification for propane HD-5 apply to propane that is intended primarily for engine fuel. Because most domestic U.S. LPG is handled through copper tubing, which could fail if corroded, all products must pass the copper strip corrosion test. A test value of No. 1 represents a LPG noncorrosive to the copper. 

Load bend fatigue strength of alloys capable of withstanding 4—5 cycles before failure in 0—90—0 degree cycles, which is above the three-cycles-to-failure minimum in MIL-S l D-883 values pertain to a 0.25-mm thick strip that has been sheared to 0.45-mm width. 

The mixture is kept for 3 hours at 105°C after the oxide addition is complete. By this time, the pressure should become constant. The mixture is then cooled to 50°C and discharged into a nitrogen-filled botde. The catalyst is removed by absorbent (magnesium siUcate) treatment followed by filtration or solvent extraction with hexane. In the laboratory, solvent extraction is convenient and effective, since polyethers with a molecular weight above about 700 are insoluble in water. Equal volumes of polyether, water, and hexane are combined and shaken in a separatory funnel. The top layer (polyether and hexane) is stripped free of hexane and residual water. The hydroxyl number, water, unsaturation value, and residual catalyst are determined by standard titration methods. 

Sulfur dioxide concentrations in oleum ate rarely specified or measured, but typical values are considerably higher than in acids of <99 wt % concentrations. This occurs because oleum is produced at relatively low temperatures in the presence of appreciable SO2 in the gas phase, thus lea ding to high solubihty. It is not possible to strip SO2 from oleums by air blowing, a technique that is ftequentiy appHed to product acids of <99% concentration. 

Recovery Process. Boron values are recovered from brine of Seades Lake by North American Chemicals Corp. In one process the brine is heated to remove some water and burkeite. The remaining brine is cooled to remove potassium chloride. This cooled brine is then transferred to another crystallizer where borax pentahydrate, Na2B40y 5H20, precipitates (18). In a separate process, boron is removed by Hquid—Hquid extraction followed by stripping with dilute sulfuric acid (19). Evaporator-crystallizers are used to recover boric acid [10043-35-3] H BO. In a third process, borax is recovered by refrigerating a carbonated brine. 

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