Precursor Screening

Numerous copolymer compositions have been screened with regard to ultimate carbon fiber properties, under comparable conditions of spinning, stabilization and carbonization. Although it is evident that different compositions will require different conditions for optimal properties, it was felt that a standard screening procedure, taking care of complete stabilization (match test), and providing for a minimum of fiber breaks, should help to select potential candidates. 

The quality of the carbon fibers was evaluated mainly from the tensile properties, modulus E and tensile strength a. Sonic modulus was used instead of tensile modulus, because the method appeared to be more reliable. Apart from E, and a, the carbon fiber density q was determined. 

---

In Section 4 we report on a broad precursor screening with regard to polymer composition, additives, influence of spinning parameters, stabilization and carbonization conditions. 

The precursors investigated can be divided into groups, such as systems known in the literature, transition-metal chlorides, and novel systems. As a start-off, silica was selected as support material, as previous SILP studies used this material successfully. The IL [BMMIM][OTf was chosen for the precursor screening, because it provides good hydrolytic stability and reasonable solubility for the substrates [60]. 

In chemical activation processes, the precursor is first treated with a chemical activation agent, often phosphoric acid, and then heated to a temperature of 450 -700 °C in an activation kiln. The char is then washed with water to remove the acid from the carbon. The filtrate is passed to a chemical recovery unit for recycling. The carbon is dried, and the product is often screened to obtain a specific particle size range. A diagram of a process for the chemical activation of a wood precursor is shown in Fig. 3. 

A reported method for the screening for transformation products of a number of pesticides [16] provides an elegant example of the complementary nature of the product-ion, precursor-ion and constant-neutral-loss scans (see Section 3.4.2 above). 

In this work, various conditions have been used for preparing catalysts to screening out a proper one mainly for CTA hydrogenation. The palladium precursor, impregnation time, calcination and reduction will be taken into account. 

Tian, Q. et al., Screening for anthocyanins using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry with precursor-ion analysis, product-ion analysis, common-neutral-loss analysis, and selected reaction monitoring, J. Chromatogr. A, 1091, 72, 2005. 

Precursor-ion Scanning Selecting m/z To monitor compounds which in CID give an identical fragment (screening)... 

If only partial screening is present, the fractal dimension takes a value somewhere between df and df. According to this model, a crosslinker deficiency, which leads to a more open structure and therefore a lower value of du increases the value of n. Dilution of the precursor with a non-reactive species has the same effect on the relaxation exponent. 

By screening 53 Rhodococcus and Pseudomonas strains, an NHase-amidase biocatalyst system was identified for the production of the 2,2-dimethylcyclopropane carboxylic acid precursor of the dehydropeptidase inhibitor Cilastatin, which is used to prolong the antibacterial effect of Imipenem. A systematic study of the most selective of these strains, Rhodococcus erythropolis ATCC25 544, revealed that maximal product formation occurs at pH 8.0 but that ee decreased above pH 7.0. In addition, significant enantioselectivity decreases were observed above 20 °C. A survey of organic solvent effects identified methanol (10% v/v) as the... 

Phosphors for CRTs are predominantly based on zinc and cadmium sulfides. Selected CRT phosphors are listed in Table 1 which also includes their precursors, their P-numbers , and their uses. (The system used to classify CRT phosphors came from JEDEC, the former Joint Electronic Device Engineering Council, now JT- Committee on Phosphor and Optical Characteristics within the Electronic Industries Association. JEDEC established the original code for these phosphors in terms of P-numbers .8 Many manufacturers of CRTs use these when specifying phosphor screen characteristics.) Although the precursors are tabulated, the mole ratios used in the syntheses are not. 

The ThinPrep Pap Test is a replacement for conventional method of Pap smear preparation for screening of cervical cancer and its precursor lesions. 

---