Sealed-screen method

Microwave-assisted reactions allow rapid product generation in high yield under uniform conditions. Therefore, they should be ideally suited for parallel synthesis applications. The first example of parallel reactions carried out under microwave irradiation conditions involved the nucleophilic substitution of an alkyl iodide with 60 diverse piperidine or piperazine derivatives (Scheme 4.22) [76]. Reactions were carried out in a multimode microwave reactor in individual sealed polypropylene vials using acetonitrile as solvent. Screening of the resulting 2-aminothiazole library in a herpes simplex virus-1 (HSV-1) assay led to three confirmed hits, demonstrating the potential of this method for rapid lead optimization. 

The technique of choice for screening crystallization conditions is the vapour diffusion hanging drop described in Chapter 3. in this method drops containing different concentrations of protein-DNA mixtures, buffer, additive, and precipitant are suspended from a sihconized coverslips placed over sealed reservoirs containing different precipitant... 

Mesuere et al. [99] and Gerringa et al. [100] have reviewed methods for the determination of copper in soils. Residual copper(II) complexes have been determined in soil by electron spin resonance spectroscopy. Fast neutron activation analysis has been studied [101] as a screening technique for copper and (zinc) in waste soils. Experiments were conducted in a sealed tube neutron generator and a germanium y-ray detector. 

EPA (1986) outlines the most common procedures for making measurements and describes conditions that should exist at the time of the measurement. The simplest, least expensive method of radon measurement is with charcoal-adsorption. One side of the container is fitted with a screen to keep the charcoal in and allow the radon to diffuse into the charcoal. The adsorbed radon subsequently decays, depositing decay products in the charcoal. After exposure for 3 to 7 days the canister is sealed and sent to the laboratory where the charcoal is placed directly into a gamma detector. 

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