Primary characterization

Numerous techniques have been applied for the characterization of StOber silica particles. The primary characterization is with respect to particle size, and mostly transmission electron microscopy has been used to determine the size distribution as well as shape and any kind of aggregation behavior. Figure 2.1.7 shows a typical example. As is obvious from the micrograph, the StOber silica particles attract a great deal of attention due to their extreme uniformity. The spread (standard distribution) of the particle size distribution (number) can be as small as 1%. For particle sizes below SO nm the particle size distribution becomes wider and the particle shape is not as perfectly spherical as for all larger particles. Recently, high-resolution transmission electron microscopy (TEM) has also revealed the microporous substructure within the particles (see Fig. 2.1.8) (51), which is further discussed in the section about particle formation mechanisms. 

Comeau, D.E. Ikenaka, K. Tsung, K.L. Inouye, M. Primary characterization of the protein products of the Escherichia coli ompB locus structure and regulation of synthesis of the OmpR and EnvZ proteins. J. Bacteriol., 164, 578-584 (1985)... 

Kerklaan, P., Bouter, S. Mohn, G. (1983) Isolationof a mutant of Salmonella typhimurium strain TAI 535 with decreased levels of glutathione (GSH-) primary characterization and chemical mutagenesis studies. Mutat. Res.. 122, 257-266... 

Ambartsumian, A.A., Tozalakian, P.V., Bazukian, I.L., and Popov, Y.G., Phenylalanine-ammonia lyase from Helianthus tuberosus L. isolation and primary characterization, Biotekhnologiya, 2, 24—28, 2000. 

A primary characterization of perovskite-type oxides must include textural analysis and X-ray identification of the phase(s) present. For a more detailed characterization, structural analysis for establishing the lattice position of cations and surface analysis (by means of techniques such as XPS) for defining the surface concentration and oxidation states of cations are desirable. Consequently, information provided by these techniques will furnish the essential criteria for comparing the different preparation methods. For convenience, we will classify the methods used to date for the preparation of pure perovskite phases according to the scheme proposed by Courty and Marcilly (29) for the whole field of mixed oxides. Table I gives a survey of methods used as a function of the phenomena on which they are based. 

The hydrothermal experiments to prepare the VOPO and VOPRO materials are quite simple. An aqueous solution of the organic template, the vanadium source and the phosphate or phosphonate are treated at 150-200°C for 3 days. It appears that in most cases, the crystals form at the reaction temperature and not upon cooling the reaction mixture and, in fact, with reaction temperatures much <150°C, that the formation of well-crystallized products occurs slowly. These well-crystallized samples are imperative to any study of these systems as single crystal X-ray diffraction is the primary characterization tool for these materials. 

A standardized work flow for strain acquisition, strain purification, primary characterization, and where necessary, classical strain improvement was initiated in our laboratories in 2(X)8 and designated the strain supply chain (SSC). The introduction of these four standardized systematic work processes has resulted in a faster and more resource-efficient development of new strains, both wild-type strains and classically improved strains, for new product development. It is presented here to serve as an inspiration for other groups seeking to systematize their strain-screening activities (Figure 10.1). 

Primary characterization of each strain is performed to get initial knowledge about the strains and to determine their suitability for further product development. The strains are characterized for both desirable and undesirable traits, e.g., growth rate in varions fermentation media as an example of a positive trait, or atypical resistance to antibiotics as an example of an undesirable trait. The primary characterization of strains in the SSC consists of several different phenotypic tests, typically performed in 96-well microtiter plates, in volumes of 100-200 jd. In order to allow fast throughpnt and high accuracy, several processes are automated, as described in Section 10.2.1. A fiiU primary characterization of a collection of strains in microtiter plate can be completed in 2 weeks. 

All strains are tested for resistance to the antibiotics tetracycline and erythromycin as part of the primary characterization. Resistance to these antibiotics is frequently observed in natural isolates from a variety of food and feed sources (Domig et al., 2008). Since antibiotic resistant microbes are undesirable in the food chain, resistant strains will not normally be selected for further product development work. Additional extensive antibiotic-resistance testing is done at a later stage to rule out the presence of resistance to other antibiotics with relevance to medical and veterinary practice. 

The availability of an easily retrievable, microtiter plate-based strain-screening collection also opens the possibiUty to test large collections for more specific parameters like bioconversion of certain compounds or production of specific metabolites in a very short time. Combining the data from such specific screens with the data generated in the primary characterization provides a good starting point for targeted product development activities. 

Light microscopy is one of the discipline s primary characterization techniques. It allows the forensic scientist to quickly address that most fundamental question, what does the sample look like before proceeding with more extensive, often destructive, analyses. At all levels of sophistication (from hand lenses to compound microscopes), optical microscopy reveals... 

S. O. Shekhtman, G. S. Yablonsky, J. T. Cleaves, and R. Fushimi. State defining experiment in chemical kinetics—primary characterization of catalyst activity in a TAP experiment. Chemical Engineering Science, vol. 58, pp. 4843-4859, 2003. 

The development of modem miniaturized electronic devices relies heavily on the use of thin epitaxial films of which the relevant physical projjerties sensitively depend on their thickness and on their microstmcture. In recent years high-resolution electron microscopy has extensively been applied for the primary characterization of such films. In particular various modes of accommodating the misfit between a single-crystal substrate and the epitaxial films have been discovered by this method. 

Our efforts in this area were initiated in 1995 with investigations of the electrodeposition of silver (26, 27) and, soon thereafter, platinum (28) nanoparticles on HOPG surfaces. The primary characterization tool employed in these experiments was ex situ non-contact atomic force microscopy (NC-AFM). In the silver work, HOPG electrode surfaces were examined by NC-AFM after the application of large amplitude potentiostatic pulses with amphmdes of —100 to —500 mV (vs. Ag/Ag+) and durations of 10-50 msec in dilute silver-plating solutions. These images looked dramatically different from the... 

A very wide range of analytical techniques are used to characterize polymer materials (e.g., see references on polymer physics [49], thermal analysis [73,74], light microscopy [75,76], Raman [77, 78], x-ray scattering [79], various spectroscopies [80, 81], and a wide range of microscopy techniques [82]). A text on polymer blends also describes many polymer characterization techniques [83]. Texts on microscopy with a focus on biological materials are often useful for the polymer microscopist (e.g., [84,85]) as the materials have in common a tendency to be soft, to require contrast enhancement, and to suffer from radiation damage in electron beam instruments. The primary characterization of an... 

After its identification in 1981 as a novel distinct immunodeficiency syndrome ( acquired rather than primary ) characterized by a depletion of CD4 T cells and an expansion of activated CDS T cells, in 1983 acquired immunodeficiency syndrome (AIDS) was finally associated with human immunodeficiency virus (HIV) in a causative way [1,2], Following the... 

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