Microscale heterogeneity

Gottlein A, Matzner E. Microscale heterogeneity of addity related stress-parameters in the soil solution of a forested cambic podzol. Plant Soil 1997 192 95-105. 

Seymour, J. R., Mitchell, J. G., and Seuront, L. (2004). Microscale heterogeneity in the activity of coastal bacterioplankton communities. Aquat. Microb. Ecol. 35, 1—16. 

All three suggested polymerization routes proceed more efficiently at higher reactant concentrations hence, microscale heterogeneity may be important in the formation of aquatic humic substances. There are many possible examples ... 

Contents of trace elements in soil materials from natural as well as from contaminated sites show a high variability in both dimensions, horizontal and vertical. Soil is not homogenous, and the microscale heterogeneity creates a real problem in representative sampling. Thus, the reproducibility and comparability of analytical data for trace elements in soils have been a great concern. The procedure of soil sampling and storage has been broadly described in several publications (Mortvedt et al. 1991, Sparks etal. 1996, Tan 1995). 

The small injection volume of CE is desirable only when a small amount of sample is available. With materials which are heterogeneous on a microscale the need for extraction/dissolution of representative... 

Contaminant precipitation involves accumulation of a substance to form a new bulk solid phase. Sposito (1984) noted that both adsorption and precipitation imply a loss of material from the aqueous phase, but adsorption is inherently two-dimensional (occurring on the solid phase surface) while precipitation is inherently three-dimensional (occurring within pores and along solid phase boundaries). The chemical bonds that develop due to formation of the solid phase in both cases can be very similar. Moreover, mixtures of precipitates can result in heterogeneous solids with one component restricted to a thin outer layer, because of poor diffusion. Precipitate formation takes place when solubility limits are reached and occurs on a microscale between and within aggregates that constitute the subsurface solid phase. In the presence of lamellar charged particles with impurities, precipitation of cationic pollutants, for example, might occur even at concentrations below saturation (with respect to the theoretical solubility coefficient of the solvent). 

Rogers EW, de Oliveira MF, Berlinck RGS, Konig GM, Molinski TF (2005) Stereochemical Heterogeneity in Verongid Sponge Metabolites. Absolute Stereochemistry of (+)-Fistularin-3 and (+)-ll-ep(-Fistularin-3 by Microscale LCMS-Marfey s Analysis. J Nat Prod 68 891... 

In this context, the aim of this study is to use a microscale (5 cm resolution) two-dimensional sampler to investigate (i) the heterogeneity of the microscale distributions of phytoplankton biomass and bulk-phase seawater viscosity, (ii) the potential changes in these distributions over the course of a P. globosa spring bloom and (iii) the nature of the correlation between seawater viscosity and phytoplankton before, during and after the formation of foam in the turbulent surf zone. 

In the iceberg model, the structure of the medium on a microscale is heterogeneous. Flow processes would involve slip between the iceberg and the film. No Si-O-Si bonds need be broken. At present, it seems that both the discrete-polyanion model and the iceberg model probably contribute to the structure of liquid silicates. In a sense, the iceberg model is the most complete model because it involves the discrete polyanions as well as the SiOj entities called icebergs. 

Mouritsen OG, Jorgensen K. Microscale, nanoscale and mesoscale 49. heterogeneity of lipid bilayers and its influence on macroscopic membrane-properties. Mol. Membr. Biol. 1995 12 15-20. 

Nasdala L, Pidgeon RT, Wolf D (1996) Heterogeneous metamictization of zircon on a microscale. Geochim Cosmochim Acta 60 1091-1097... 

A general discussion of the rheology of suspensions and other materials that are heterogeneous at the microscale is beyond the scope of the present book. However, the interested reader may wish to refer to the original paper of Batchelor21 or to the textbooks of Schowal-ter, Russel et al., or Larson for a more comprehensive presentation of this material.22... 

The use of microscale reactors is not confined to single-phase systems. Both striated and droplet flows of two-phase liquid mixtures have been studied, as have suspensions of solid particles. It seems that almost any chemistry can be used at the microscale. Effectiveness factors in heterogeneous catalysis will be nearly 1.0 since diffusion distances are so small. As pointed out below, rapid molecular diffusion gives nearly instantaneous cross-channel mixing and may cause significant axial mixing. 

Somewhere between the sizes of an atom and a grain of sand lies the realm of small particles called colloids. As will become evident, they are everywhere. The simplest colloidal materials, also generally known as suspensions or dispersions, consist of two mixed phases. The continuous or dispersing phase may be gas, liquid, or solid (or even plasma, the fourth phase of matter). Air, water, and plastics are common examples. The colloid particles make up the dispersed or suspended phase when uniformly distributed in the second, continuous phase. The dispersed matter may also be gas, liquid, or solid, and any combination in more complex suspensions. Colloidal dispersions are considered homogeneous mixtures even though they can be heterogeneous at or below the microscale. 

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