Surface determinations

Harder P, Grunze M, Dahint R, Whitesides G M and Laibinis P E 1998 Molecular conformation in oligo(ethylene glycol)-terminated self-assembled monolayers on gold and silver surfaces determines their ability to resist protein adsorption J. Rhys. Chem. B 102 426-36... 

One of the most important uses of specific surface determination is for the estimation of the particles size of finely divided solids the inverse relationship between these two properties has already been dealt with at some length. The adsorption method is particularly relevant to powders having particle sizes below about 1 pm, where methods based on the optical microscope are inapplicable. If, as is usually the case, the powder has a raiige of particle sizes, the specific surface will lead to a mean particle size directly, whereas in any microscopic method, whether optical or electron-optical, a large number of particles, constituting a representative sample, would have to be examined and the mean size then calculated. 

Value of fl = S ISf, for a number of solids and various vapours (S and S p are the specific surfaces determined by use of nitrogen and of another vapourt respectively]... 

Filter aids should have low specific surface, since hydraulic resistance results from frictional losses incurred as liquid flows past particle surfaces. Specific surface is inversely proportional to particle size. The rate of particle dispersity and the subsequent difference in specific surface determines the deviations in filter aid quality from one material to another. For example, most of the diatomite species have approximately the same porosity however, the coarser materials experience a smaller hydraulic resistance and have much less specific surface than the finer particle sizes. 

The Sorptometer appears to offer several ad, vantages for use in determining the surface area of fine powdered proplnt ingredients. By comparing the specific surface determined by N2 adsorption with the specific surface determined by other methods, an estimate of the deviation of the particles from a sphere can be made. For many very fine powders, N2 adsorption is one of the few methods available for describing the, size of the particles... 

Tyndall, G. W. and Waltman, R. J., Thermodynamics of Confined Perfluoropolyether Film on Amorphous Carbon Surface Determined from the Time-Dependent Evaporation Kinetics," J. Phys. Chem. B, Vol. 104,2000, pp. 7085-7095. 

Figure 21. Family of reactive trajectories in the ground adiabatic potential energy surface determined by Eq. (13). Crosses indicate the caustics. Taken from Ref. [29].

The reduced magnetite with alumina was found to have a N2 BET surface area of 29 m per gram of catalyst. When adsorbing N2 dissociatively it was found that 2.2 mL [standard conditions, i.e. 273 K and 1 bar (= 100000 Pa)] of N2 could be adsorbed per gram of catalyst. Assuming that the atomic nitrogen forms a c(2x2) overlayer on the Fe(lOO) surface determine the iron area per gram of catalyst. The lattice distance of iron is 0.286 nm. 

The majority of heterogeneous chemical and physical-chemical processes lead to formation of the intermediate particles - free atoms and radicals as well as electron- and oscillation-excited molecules. These particles are formed on the surface of solids. Their lifetime in the adsorbed state Ta is determined by the properties of the environment, adsorbed layer, and temperature. In many cases Ta of different particles essentially affects the rate and selectivity of heterogeneous and heterogeneous-homogeneous physical and chemical processes. Therefore, it is highly informative to detect active particles deposited on surface, determine their properties and their concentration on the surface of different catalysts and adsorbents. 

The surface-to-volume ratio s indicated in Table III include the furniture. Their standard deviation is estimated at 20 % and comes mainly from the surface determination of the furniture.These ratio s are rather high compared with values reported in the literature (see Table V), although our rooms had normal dimensions. 

The kinetics of the CTMAB thermal decomposition has been studied by the non-parametric kinetics (NPK) method [6-8], The kinetic analysis has been performed separately for process I and process II in the appropriate a regions. The NPK method for the analysis of non-isothermal TG data is based on the usual assumption that the reaction rate can be expressed as a product of two independent functions,/ and h(T), where f(a) accounts for the kinetic model while the temperature-dependent function, h(T), is usually the Arrhenius equation h(T) = k = A exp(-Ea / RT). The reaction rates, da/dt, measured from several experiments at different heating rates, can be expressed as a three-dimensional surface determined by the temperature and the conversion degree. This is a model-free method since it yields the temperature dependence of the reaction rate without having to make any prior assumptions about the kinetic model. 

Figure 4c shows one example of the time course of an SPR angle shift during exposure of a NH2-SAM to culture medium supplemented with 2% fetal bovine serum (FBS). It also includes the time course of the fraction of adherent cells on the same surface determined by TIRFM observation (Fig. 2). The SPR angle shift rapidly increased, and then leveled off within a few minutes. Cells adhered much more slowly than proteins. Those results indicated that serum proteins in a medium rapidly adsorbed to the surface then, cells interacted with the adsorbed protein layer, as shown schematically in Fig. 5.

Kaplan, M.R., Calef, E., Bercovici, T., and Gitler, C. (1983) The selective detection of cell surface determinants by means of antibodies and acetylated avidin. Biochim. Biophys. Acta 728, 112-120. 

It was found in this work that the concentration of hydroxyl species on the surface determines the extent of Fe(C0)5 decomposition on Ti02 T e concentration of reduced titanium cations (T 3+) on the surface apparently has no effect on the process. Neither concentration affects the nature of the species formed. 

Surface lattice structure Density of active surface atoms and reactivity of the surface determined by the crystalline orientation of silicon/electrolyte interface... 

Bearing in mind that diffusing ions move randomly in all directions, it is reasonable to say that the diffusing ions sense selfsimilar scaling property of the electrode surface irrespective of whether the fractal surface has self-similar scaling property or self-affine scaling property. Therefore, it is experimentally justified that the fractal dimension of the self-affine fractal surface determined by using the diffusion-limited electrochemical technique represents the apparent self-similar fractal dimension.43... 

The lack of knowledge of precise values of the roughness factor makes it difficult to compare data reported from different studies. This applies in particular to the double-layer capacity data, the values of surface concentration of the adsorbates, and the rates of electrochemical reactions. Therefore, the question of how to determine the real surface of the electrode is of cmcial importance. A survey of various methods for determining roughness was given by Trasatti and Petrii. For noble metal electrodes, the charges of hydrogen deposition and surface oxide formation can be utilized in real-surface determination." ... 

Fig. 4. Cell interactions, cell surface determinants and cytokines in the ACAID pathway to CDS suppressor T cells. 

Gaseous fragments are eliminated on heating, and numerous chemical species are formed at the reacting surface of the azide polymer. The heat transfer process from the high-temperature zone to the reacting surface determines the burning rate of an azide polymer. 

In periphery-functionalized dendritic catalysts, the functional groups at the surface determine the solubility and miscibility and thus the precipitation properties. Many dendrimers functionalized with organometallic complexes do not dissolve in apolar solvents, and the presence of multiple metal centers at the periphery facilitates precipitation upon addition of this type of solvent. It is emphasized that the use of dendrimer-immobilized catalysts with the goal of recovery through precipitation is worthwhile only if the tendency to precipitation of the dendritic system exceeds that of its non-dendritic equivalent. 

The reflection of light from a smooth solid surface determines the degree of polish. The industrial applications are many, considering the impact of design and appearance on both sales and the product (cars, household appliances, furniture). A very sensitive procedure for the determination of surface roughness has been to use atomic force microscope (AFM Birdi, 2003). 

Finally, consider side-by-side deactivation. Whatever the concentration of reactants and products may be, the rate at which the poison from the feed reacts with the surface determines where it deposits. For a small poison rate constant the poison penetrates the pellet uniformly and deactivates all elements of the catalyst surface in the same way. For a large rate constant poisoning occurs at the pellet exterior, as soon as the poison reaches the surface. 

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