Telescoping

One of the most widely used methods to improve overall process efficiency is to reduce the number of steps and unit operations in a synthetic route. This is more commonly known as telescoping. This can lead to more efficient, less wasteful processes that require fewer solvents because of the smaller number of steps. An example of this technique was illustrated earlier in Section 3.1.6, where the process optimization of the sertraline (Zoloft ) production process by Pfizer was described. In this case the number of process steps (unit operations) was reduced from 3 to 1, which led to huge savings due to higher productivity, fewer inputs, and less waste generation [18]. 

Although several methods are used to reduce or ehminate solvent consumption within a pharmaceutical process, solvents are often used in excess in order to carry out reachons in a dilute environment because of solubihty and product selectivity issues [2]. As solvents still have a great influence on the quality of the final products, it can be very difficult to find suitable replacements [43]. It is therefore desirable to find solvents for a process that can be easily recovered, separated, and purified for reuse. Spent solvents that are not recovered must be disposed of as wastes, which can be quite costly and add to the environmental burden. 

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High angular resolution studies with modem THz telescopes and interferometric arrays can even probe the... 

These alloys are of vital importance in the construction of modern aircraft and rockets. Aluminum, evaporated in a vacuum, forms a highly reflective coating for both visible light and radiant heat. These coatings soon form a thin layer of the protective oxide and do not deteriorate as do silver coatings. They are used to coat telescope mirrors and to make decorative paper, packages, toys. 

Figure 4.16 Schematic illustration showing how an experimental plot of modulus against log t (a) can be telescoped (b) by shifting successvie segments by an amount designated as log a.

Since 1963 spectra of many molecules have been detected, mainly in emission but some in absorption. Telescopes have been constructed with more accurately engineered paraboloids in order to extend observations into the microwave and millimetre wave regions. 

The first polyatomic molecule was detected in 1968 with use of a telescope having a dish 6.3 m in diameter at Hat Creek, California, USA, designed to operate in the millimetre wave region. Emission lines were found in the 1.25 cm wavelength region due to NH3. The transitions are not rotational but are between the very closely spaced 2 = 0 and 2 = 1 levels of the inversion vibration V2 (see Section 6.2.5.4). 

Figure 9.34 A LIDAR device using a Cassagrain telescope...

Synthesis gas is obtained either from methane reforming or from coal gasification (see Coal conversion processes). Telescoping the methanol carbonylation into an esterification scheme furnishes methyl acetate directly. Thermal decomposition of methyl acetate yields carbon and acetic anhydride,... 

Schott Zerodur P-quart2 soHd solution, Si02 2ero expansion electric range tops, telescope mirrors... 

Thermal Properties. Many commercial glass-ceramics have capitalized on thek superior thermal properties, particularly low or zero thermal expansion coupled with high thermal stabiUty and thermal shock resistance properties that are not readily achievable in glasses or ceramics. Linear thermal expansion coefficients ranging from —60 to 200 x 10 j° C can be obtained. Near-zero expansion materials are used in apphcations such as telescope mirror blanks, cookware, and stove cooktops, while high expansion frits are used for sealing metals. 

The value of the beam divergence angle given by equation 3 corresponds to that emerging from the laser. The beam may be collimated further by a telescope. The improvement of the coUimation is the inverse of the magnification of the telescope ... 

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