Source, switchable

A variation of the idea of electromagnetic taggants has been proposed, called detonator deactivation. In this concept, a reed switch is connected in series with a detonator bridge wire. Illumination of the detonator by a switchable electromagnetic source would cause the reed to open. A number of methods are possible to ensure that the reed could not be subsequently closed. The advantages of the concept are twofold ... 

Clearly this is the least mature field within the solvent alternatives arena however, this also means that, as with tailor-made ionic liquids, it is likely that tailor-made switchable solvent systems will continue to advance and become an increasingly important area of research during the coming decades. As with all areas of clean technology, synergies and overlaps with other areas of sustainable development will increase and lead to new advances. For example, in the area of gas expanded liquids, the focus has so far been on petroleum-sourced VOCs and therefore significant advances could be made by investigating other types of gas expanded media, whether they be renewably sourced VOCs or non-volatile alternatives. 

FIGURE 15.6 A schematic diagram showing the external ion source of the ion trap with an off-axis detector. The source is switchable between El and CL Analytes ions are created in the ionization chamber outside the ion trap. Subsequently, analyte ions are injeeted into the ion trap through lenses. 

Hewlett Packard, for example, supply the HP 5988A and HP 5987A mass-selective detectors for use with LC (see Appendix 1). This particle beam LC-MS uses the same switchable electron impact chemical ionisation source and the same software and data systems that are used for a GC-MS system. Adding a GC creates a versatile particle-beam LC-GC-MS system that can be switched from LC-MS to GC-MS in an instant. 

Fig. 4.62. hQh-ICR hybrid instrumentation. This instrument is equipped with an ESI-to-MALDI switchable ion source that makes use of a two-stage ion funnel (d), ) to focus ions into a RF hexapole ion guide (h, ). The ions then pass a quadmpole ( ) that may either be mn as band pass (q) or as mass-selective device (Q) and then reach a multifunctional RF hexapole ion trap (h, ) where they can be i) accumulated, ii) coUisionally activated, or Hi) reacted with radical anions from the NCI source to effect ETD as required. For mass analysis the ions are then guided via an RF-oiily hexapole ( ) into the ICR cell ( ) where a hollow cathode ( ) is attached for BCD. Schematic of Bruker Solarix instrument series by courtesy of Bruker Daltonik, Bremen. 

A further interesting use of the focal-conic to homeotropic texture transition is in infrared modulation [272]. Here it was found possible to modulate infrared light at A=8-12 pm with a maximum transmission of 87%, a contrast of 93%, and turn on and off times of 1 ms and 125 ms, respectively. A further window examined was 3-5 pm, and this work suggests that other chiral nematic electrooptic effects could be exploited in the near infrared. In communications technology a 2x2 optical switch for fiber-optics has been developed [273] using a chiral nematic film and two switchable nematic waveplates. It has been demonstrated that this is suitable for LED or laser sources. The device worked at 1.318 pm and had switching times of 40 ms with -26 dB crosstalk between unselected fibers. There will clearly be further advances in this use of the unique optical properites of chiral nematics. 

In a follow-up study by the same research group, this methodology was used to investigate the effects of different pig rearing systems on the quality of the final product of dry-cured Iberian ham. In this work, a switchable reagent ion source was used to generate H3O +,... 

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