Bonn procedures

The cumulative sums of selected major and trace metals extracted by the two SSD procedures from representative arid-zone soils are shown in Fig. 4.6. As can be seen from the figure, the Rehovot procedure is stronger in attacking desired fractions, such as the carbonate bound, Mn oxide bound and organically bound fractions. Extraction of certain major elements, indicating selectivity, specificity and completeness of extraction of given soil components, was found to differ between the two procedures. Calcium and Mg were more completely extracted from the carbonate fraction in arid zone soils by the Rehovot procedure. Calcium and relevant trace elements bound in the carbonate fraction, which were not completely dissolved by the Bonn procedure at this step, were released at the following steps, such as the ERO, OM or RO fractions. 

On the basis of this comparison study, at present, it is still difficult to adopt a universal selective sequential dissolution procedure, which may be used everywhere and be suitable for all soils with diversified physical, chemical and mineralogical properties. The application of the SSD procedure must consider individual soil characteristics, such as soil type and properties. The two typical SSD procedures were developed to address soils formed in two climates. The Rehovot procedure was developed to be suitable for the calcareous soils in arid and semi-arid zone soils, whereas the Bonn procedure was created to primarily handle the acid and neutral soils in humid zones. In general, the Bonn procedure appears to be unsuited for calcareous soils in arid and semi-arid zones. The Rehovot procedure has limitations in handling acid and neutral soils, especially forest soils with higher content of organic matter. 

The two representative selective sequential dissolution procedures (Bonn and Rehovot procedures) were employed to comparatively study the distribution of trace elements in Israeli arid soils (Table 4.4). The results of both experiments have been fully reported by Banin et al. (1995) and Han and Banin (1995). 

Fig. 4. Scatchard plots for the binding of tilorone hydrochloride to calf thymus DNA (a) Me. lysodeikticus DNA (b) poly (dA-dT) poly (dA-dT) (c) and poly (dG-dC) poly (dG-dC) (d). Each different symbol corresponds to a separate experiment. Thus, each figure represents a set of 4 or 5 separate experiments, r is moles of bound tilorone/base pair concentration and (u) is the concentration of unbound tilorone. Equilibrium dialysis was carried out by a procedure and an apparatus (Dianorm, supplied by Dr. Virus KG, Bonn, Germany) described by Weder et al.61 Dialysing membrane (0.02S mm thick) was sandwiched between two halves of a Teflon (round) macro-cell (dialysable volume = 1 ml). The DNA, or labelled tilorone solutions were introduced by separate micro syringes on either side of the membrane through the side valves. The valves were closed air tight and the macro-cells were fixed into a rotating machine. All equilibrium dialysis studies were carried out at 20°, and at 10 rotations/min. Under these conditions equilibrium was attained in 4-5 hr. After the equilibrium was reached 0.8 ml of the solution from either side of the membrane was withdrawn by microsyringes and the radioactivity was determined using dioxan scintillation fluid...

The first cascade molecule was described in 1978. Since then, several thousands of papers have been published, including several books and review articles.Some procedures of dendrimer preparation are patented." Ref. 3c by M. Fischer and F. Vogtle contains 76 citations covering thoroughly the field (F. Vogtle, Institute of Organic Chemistry, Bonn, Germany). 

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