Evidence from Nature

However, it has been suggested [26] that natural epitaxial coarsening of diamonds could proceed in colloidal pneumatolytic-hydrothermal environments in near-superficial earth zones, because equilibrium data for material trapped as inclusions in diamond indicated closing temperatures of 600-800 C and pressures below 10 MPa [15] and fit to early theories of diamond formation [27]. Based on the petrologic circumstances mentioned in [26], an area of probable diamond hydrogenesis and hydrosynthesis was sketched (Fig. 1). 

Theoretical calculations and experimental studies [28] suggested that smaller, colloidal diamond particles of about lOnm may be stable at lower pressures and higher temperatures than macroscopic diamond. A so called crystallite size effect [29] might account for metastable diamond nucleation and growth under hydro-thermal conditions. Thus, the HPHT graphite-diamond equilibriiun should only be applied to crystallites 100nm in diameter [28]. 

Based on observations of turbid rims of fibrous diamond and layers of the lons-daleite polymorph on some natmal diamonds [30] as well as of embryocrystals and phantoms in central parts of natural diamonds [31], a mechanism for homoepitactic diamond coarsening and crystal growth in nature was presented [32,33]. Assuming 

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Suksi J, Ruskeeniemi T, Rasilainen K (1992) Matrix diffusion- evidences from natural analogue studies at Palmottu in SW Finland. Radiochim Acta 58/59 385-393... 

Bau, M. Usui, A. Pracejus, B. Mita, N. Kanai, Y. Irber,W. Dulski, P. (1998) Geochemistry of low-temperature water-rock interaction evidence from natural waters, andesite, and iron-oxyhydroxide precipitates at Nishiki-numa iron-spring, Hokkaido,.Japan. Chem. Geol. 151 293-307... 

Carlson, P.R., and Forrest, J. (1982) Uptake of dissolved sulfide by Spartina altemiflora evidence from natural sulfur isotope abundance ratios. Science 216, 633-635. 

Moran, M.A., Wicks, R.J., and Hodson, R.E. (1991) Export of dissolved organic matter from a mangrove swamp ecosystem evidence from natural fluorescence, dissolved lignin phenols, and bacterial secondary production. Mar. Ecol. Prog. Ser. 76, 175-184. 

Despite the paucity of evidence from natural samples for carbonate being stable in the mantle, there has been much experimental work since the 1970s devoted to understanding the behavior of oxidized carbon (as CO2 and carbonate) at pressure and temperature conditions of the Earth s mantle (see reviews by Wyllie, 1995 Luth, 1999 Wyllie and Ryabchikov, 2000). As outlined by Eggler and Baker (1982) and by Luth (1993), understanding the stability of oxidized carbon provides fundamental constraints on the stability of reduced carbon in mantle mineral assemblages. 

The early work on phosphate glasses led to the idea that crystalline phosphates might make extremely durable waste forms, particularly for actinides. The earliest suggestion was for the use of monazite (Boatner 1978, Boatner et al. 1980, McCarthy et al. 1978, 1980). The attractive qualities of monazite as a nuclear waste form are (1) a high solubility for actinides and rare earths (10 to 20 wt %) (2) evidence from natural occurrences of good chemical durability (3) an apparent resistance to radiation damage, as natural monazites are seldom found in the metamict state, despite very high alpha-decay event doses (Boatner and Sales 1988). There have been extensive studies of monazite and apatite as potential waste form phases, and a considerable amount of work on a number of synthetic phosphate phases has been completed. 

Rudall, P. J. and Bateman, R. M. (2003). Evolutionary change in flowers and inflorescences evidence from naturally occurring terata. Trends in Plant Science, 8,76-82. 

Gardingen (eds), Plant Responses to Elevated CO2. Evidence from Natural Springs (Cambridge University Press, Cambridge, 1997, pp. 69-86). 

Although evidence from natural systems is useful to constrain reaction mechanisms and minerals to be incorporated into such models, time-dependent information is generally lacking. A series of laboratory column experiments have been conducted as blind test cases in order to test the capabilities of two of the currently available, coupled models to predict product solids and output fluid compositions with time. The experiments reacted single minerals of importance to the radioactive waste disposal programmes in the UK, Sweden and Switzerland, with simplified young (Na-K-Ca-OH) and evolved (Ca(OHE) synthetic cement porewater leachates. 

It may be pointed out that C-alkylation of ethyl acetoacetate is readily aooount for by the mesomeric nature of the carbanion (IV), as will be evident from the following ... 

In addition the very effective adsorbents for noble metals have been obtained. Their high soi ption capacity (SSC) and coefficients of intei phase distribution (D) are evidence availability of their use for concentration and isolation the microquantities of these metals from natural and induced objects. 

Reactive control can alter the line length ( f LC) to the level at which the system will have the least possible swings. It is evident from these curves that an uncompensated line of a much shorter length may not be able, to transfer even its natural load (Pq) successfully. This is due to the steeply drooping characteristics of the voltage profile at about this load point, which may subject the... 

That the degree of comminution on its own is not the only factor involved in the kinetics-of the release of the active principles, but that evidently the nature and amount of the accompanying substances also play an essential part, has been demonstrated in the case of the sennosides in aqueous preparations (hot extractions and cold macerates) from senna fruits and senna leaves [3],... 

Evidently, from the low value of the exponent in Equation 7-80, the contribution from natural convection and, hence, its practical significance is small. 

Although programmed cooling crystallization clearly results in a larger mean crystal size than that from natural cooling it is also evident that some fines i.e. small crystals are also present in the product. Since the solution was seeded these fine crystals must clearly have arisen from crystal attrition or secondary nucleation (see Chapter 5). 

As known, SEC separates molecules and particles according to their hydro-dynamic volume in solution. In an ideal case, the SEC separation is based solely on entropy changes and is not accompanied with any enthalpic processes. In real systems, however, enthalpic interactions among components of the chromatographic system often play a nonnegligible role and affect the corresponding retention volumes (Vr) of samples. This is clearly evident from the elution behavior of small molecules, which depends rather strongly on their chemical nature and on the properties of eluent used. This is the case even for... 

Table I summarizes some typical distribution coefficients. Sediments become enriched in plutonium with respect to water, usually with a factor of vlO5. Also living organisms enrich plutonium from natural waters, but usually less than sediments a factor of 103 - 101 is common. This indicates that the Kd-value for sediment (and soil) is probably governed by surface sorption phenomena. From the simplest organisms (plankton and plants) to man there is clear evidence of metabolic discrimination against transfer of plutonium. In general, the higher the species is on the trophic level, the smaller is the Kd-value. One may deduce from the Table that the concentration of plutonium accumulated in man in equilibrium with the environment, will not exceed the concentration of plutonium in the ground water, independent of the mode of ingestion.

Even today renewable resources play a dominant role as raw materials for surfactants, but only because of the great contribution made by soaps to the production of surfactants. If the soaps are left out of consideration as native surfactants, petrochemistry holds 65-70% of the production of synthetic surfactants [2]. But for the future a further increase of renewable raw materials is expected in surfactant production [3]. The main reason for this development is the superior digestibility in the environment of products produced from natural materials. The future importance of the renewable raw materials becomes evident from the fact that even now new plants are cultivated or plants are modified to obtain an improved yield. A new type of sunflower has been cultivated to obtain a higher proportion of monounsaturated oleic acid compared with doubly unsaturated linoleic acid [4],... 

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