Focused arrays

The synthesis of small, focused arrays based on some of the hits may help define a series if the desired compounds are not available through substructure or similarity searching. The purpose of this type of array is not to optimize a hit but to help prioritize a series for further synthetic work. Inclusion of the original hit in the array is useful for confirmation of activity, particularly when supplies are limited or the screening sample was of low purity. 

There are many commercially available focused arrays, encompassing all areas of biological research, including toxicology. Many reports have been published using these cDNA microarrays (for example, Pennie et al. 2001 Landowskietal. 2004 Tomascik-Cheeseman et al. 2004). 

A five-step process was planned to provide a focused array of compounds incorporating three points of diversity arising from sulfonamide formation, A -alkylation, and substituent variation (Scheme 18.21). The route makes use of established reliable reactions such that the entire process was readily antomated using a Zinsser Sophas robotic platform. The first reaction uses apolymer-supported sulfonyl transferreagent, derived from the immobilization... 

More recently, the circular array was proposed to assess the reflectivity of cylindrical specimens [3]. First, a circular C-scan image was obtained. The total scan time was about 25 min., which does not include a relatively time consuming alignment of the specimen. From the circular C-scan image, circular B-scan profiles were chosen in specific planes. The transducer was a focused high frequency transducer with a center frequency of 25 MHz of the transducer bandwidth. This frequency corresponds to a wavelength of 0.11 mm and 0.25 mm in the Plexiglas specimen and the AlSi-alloy, respectively. Additional experimental parameters are presented in Table 1. 

For conventional probes, acoustic verification aims at characterizing the beam pattern, beam crossing, beam angle, sensitivity, etc., which are key characteristics in the acoustic interaction between acoustic beam and defect. For array transducers, obviously, it is also a meaning to check the acoustic capabilities of the probe. That is to valid a domain (angle beam, focus, etc.) in which the probe can operate satisfactorily. 

Similarly, the focusing capability of an array is the strongest focused beam which can be steered. The simplest way to evaluate it is to test a theoretical focusing time delay law, in the near-field and in the natural direction of propagation of the array. The beam pattern characteristics depth, lateral size and length of the focal spot must be found consistent with modelling and no lobe must appear above a predetermined level. 

Figure 3 Set-up for the dual array probe characterization a/ for angle beam measurements b/ for focused beam characterization...

Ion detectors can be separated into two classes those that detect the arrival of all ions sequentially at one point (point ion collector) and those that detect the arrival of all ions simultaneously along a plane (array collector). This chapter discusses point collectors (detectors), while Chapter 29 focuses on array collectors (detectors). 

An ion beam containing just two types of ion of m/z values 100 and 101 dispersed in space on passing through a magnetic field. After dispersal, ions of individual m/z value 100 or lOI are focused at points close to the entries of two elements of an array collector. Each element of the array is a point ion collector. 

An array ion collector (detector) consists of a large number of miniature electron multiplier elements arranged side by side along a plane. Point ion collectors gather and detect ions sequentially (all ions are focused at one point one after another), but array collectors gather and detect all ions simultaneously (all ions are focused onto the array elements at the same time). Array detectors are particularly useful for situations in which ionization occurs within a very short space of time, as with some ionization sources, or in which only trace quantities of a substance are available. For these very short time scales, only the array collector can measure a whole spectrum or part of a spectrum satisfactorily in the time available. 

Recording of the dispersed ion beams can take place simultaneously across a plane, as in an array detector, or, as described here, by being brought to a focus at one point sequentially. 

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