Mixed species

Aconite roots marketed in India are apt to be from mixed species and botanical verification of such material is desirable. 

Several mixed species have been identified in nonaqueous solutions by Se nmr spectroscopy. These include BrSeSeCl. Sc3X2 and Se4X2 " and ClSeSCl, BrSeSCl, ClSeSBr and... 

Mixed species with three different halogens have been made... 

In the past, there was quite a lot of confusion regarding the true nature of some alkaline-earth compounds. Several boride, nitride, and carbide compounds, as well as some mixed species, especially of calcium, were in doubt or at least subject to some ongoing discussion. For example, the phase relationships and structures of CaC2 phases I-IV were not well understood. The three nitride... 

Microsensors have been used to develop profiles in mixed species biofilms. Figure 10 shows concentration profiles of sulfide, oxygen, and pH in a biofilm accumulated on the surface of a mild steel corrosion coupon. The concentration of sulfide is highest near the metal surface, where iron sulfide forms quickly and covers the steel surface if both ferrous and sulfide ions are available. At low ferrous ion concentrations, adherent and temporarily protective films of iron sulfides are formed on the steel surface, with a consequent reduction in corrosion rate. High rates of SRB-induced corrosion of mild steel are maintained only in high concentrations of ferrous ion. 

The ability to compare semiochemical patterns and to assess degrees of similarity is a likely mechanism underlying the establishment, and eventually the maintenance of genetic divergence. Amongst Tamarins (Saguinus spp.) and Marmosets, both for within- and between- (related) species distinctions, the complexity of their scent marks provides a discriminatory mechanism (Epple et ai, 1987 Smith et al., 1997). Mixed species groups of these monkeys are enabled to co-exist, to... 

For the study of mixed oxides, one should characterize the various sites. In this case, the first step is to characterize the CO adsorption at various equilibrium pressures at low temperature, followed by evacuation at increasing temperatures to obtain information about the stabilities of the various species. Although the C—O stretching frequency is the most informative parameter, the data determining the stabilities of the various species can be decisive for the assignment of the bands. Multiple carbonyls adsorbed on the same metal cation are possible, and in order to identify them isotopic mixtures should be used. Sometimes the polycarbonyls are very stable and in this case, if 12CO is adsorbed first and then 13CO introduced, mixed species may not form at ambient temperature. 

Since the early disclosure by Negishi that zinc halide salts accelerate Pd(0) -catalyzed crosscouplings between vinyl zirconocenes and various halides [78], several methods have been developed that extend the utility of this metathesis process from a zirconium chloride to a zinc chloride (79 Scheme 4.47). Alternatively, routes to more reactive diorganozinc intermediates, e. g., using Me2Zn, convert readily available zinc derivatives to mixed species 80, which selectively couple with various electrophiles [14]. 

Table 16.4 provides the summary of economic costs and results. The presumption throughout is that each process can be operated with environmental and human safety to produce a fully satisfactory product of sufficient quality to command market prices. The processes which produce discrete products, i.e. methanolysis and hydrolysis, will have to meet commercial specifications. The mixed-species product processes, i.e. simple glycolysis, hybrid and glycolysis with color filtration, must be able to feed adjacent polymerization facilities to make satisfactory product. Because the simple glycolysis process has little purification capability,... 

Carbonate rocks and foraminifera tests (a sample of mixed species) are consistently lower in 5 Mg than Mg from seawater by several per mil. In addition. Mg in calcite is consistently lower in 5 Mg than Mg in dolomite by approximately 2%o (Fig. 1). These data together with the samples of coeval speleothem calcite and waters show that the heavy isotopes of Mg partition to water relative to carbonate minerals. In this respect the Mg isotopes behave much like the isotopes of Ca (Gussone et al. 2003 Schmitt et al. 2003). There is not yet sufficient data to assess with confidence the temperature dependence of the fractionation of Mg isotopes between carbonates and waters, although Galy et al. (2002) concluded that the evidence so far is that temperature effects are below detection in the range 4-18°C. 

LDAO/SDS Interaction. Mixing of cationic and anionic surfactant solutions results In the formation of a mixed species that Is more surface active than the Individual species. The enhanced synergistic effect has been explained (2,3) by showing that a close-packed adsorption of electroneutral R R takes place (R" " and R represent the long chain cation and anion respectively). In the case of Ci2 and C14-DAO, a 1 1 LDAO/SDS molar ratio produces a minimum In surface tension and Is accompanied by an Increase In pH In the bulk solution the association seems to be of the type R R", and the absence of visible precipitate may be attributed to the solubilization of the R R" complex In the solution. In the region where LDAO Is In excess, the structure Is probably [cationic (LDAOH ) anionic (SDS)] nonlonlc (LDAO), while [cationic (LDAOH anionic (SDS)] anionic (SDS) Is formed when SDS Is In excess. Equal molar concentration results In cationic (LDAOH ) anionic (SDS) complex which should favor precipitation. However, at pH >9, there Is no Indication of precipitation (even when the total solute concentration Is 0.35 M). When the pH Is below 9, then precipitation will take place. 

The concept sounds attractive, but there is a flaw in the explanation. Assuming an equilibrium situation between the two bulk phases and the interphase, complex formation at the interfacial region requires the same complexes are formed also in the bulk phases. Consequently, in order to produce a considerable amount of the mixed species MA, xBx in the liquid-liquid boundary layer some B must be dissolved in the aqueous, as weU as some A in the organic phase. Since by definition this condition is not met, the relative amount of M present at the interphase region as MAn xBx must be negligible. However, now the metal ion will be distributed between MA in the aqueous phase and MBp in the organic layer (n and p are the... 

Prior to any work on heteroatom clusters the notion was expressed (20) that heteroatom placement within the polyatomic clusters would lead to a decrease In delocalization and bonding and thence stability. Although this may lessen stability the substitution clearly does not preclude It. Furthermore, many of the likely polyhedra already have Inequlvalent atom positions, the 5, 7, 9 and 10 atom examples already considered here for example, and mixed species especially with elements from different groups may be quite stable within the discrimination provided by Inequlvalent positions. Even the nominally equivalent atom positions In a tetrahedron can obviously accommodate substantial differences. Additional examples of mixed element polycations are certainly to be expected. An Inadequate foresight was revealed In a review of polycations (20) written for a 1974 award symposium, about one year before the crypt discoveries, by the expectation that polycations should be more stable than polyanions for the metallic elements. In hindsight, metallic behavior Is a property of the dense solid state and has little to do with the stability of small clusters where electronic and geometric factors are far more important. 

An alternative formulation of the phase-transfer DCC concept was reported in 2008 by the Sanders group [75]. In this case, thiol monomers were dissolved in water on either side of a U-tube containing chloroform (Fig. 1.23). After allowing the system to reach equilibrium, monomer distribution was identical in both aqueous solutions, and mixed species (e.g., 51) were observed in the chloroform layer. 

The stepwise stability constants for V complexes with glutamic, aspartic, W -ethylenediaminedisuccinic, and W -ethylenediamine-bis-(a-glutaric acid) have been reported.The 1 1 oxovanadium(iv) complex of 5-nitrosalicylic acid has been characterized = 710 nm), and the mixed species formed between vanadium(iv) with protocatechuic acid (H3L ) or gallic acid (H L ) and 4-aminoantipyrine (aant) have been identified spectroscopically as the 1 1 1 and 1 2 2 HL (HL ) aant complexes. The species present in solutions of and tartaric acid below pH 2 have been identified as [VO-... 

A sink-float technique has been developed for separating hemlhydrate from gypsum crystals for samples from mixed species crystallizers. 

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