Physical attraction

In carbon adsorption, contaminants are physically attracted or adsorbed on the surface of the carbon. Adsorption capacities are high for carbon because its porous nature provides a large surface area relative to its volume. Activated carbon is prepared from lignite, bituminous coal, coke, wood, or other organic materials such as coconut shells. 

Rinsing Rinsing removes contaminants through dilution, physical attraction, and solubilization. Multiple rinses with clean solutions remove more contaminants than a single rinse with the same volume... 

Stokes law is rigorously applicable only for the ideal situation in which uniform and perfectly spherical particles in a very dilute suspension settle without turbulence, interparticle collisions, and without che-mical/physical attraction or affinity for the dispersion medium [79]. Obviously, the equation does not apply precisely to common pharmaceutical suspensions in which the above-mentioned assumptions are most often not completely fulfilled. However, the basic concept of the equation does provide a valid indication of the many important factors controlling the rate of particle sedimentation and, therefore, a guideline for possible adjustments that can be made to a suspension formulation. 

Surface roughness is also expected to result in depression of the capacitance semi-circle. This phenomenon, which is indeed apparent in both Figures 1 and 2, is, however, unrelated to surface area. Rather, it is attributable to surface heterogeneity, i.e. the surface is characterized by a distribution of properties. Macdonald (16) recently reviewed techniques for representing distributed processes. A transmission line model containing an array of parallel R/C units with a distribution of values is physically attractive, but not practical. An alternative solution is introduction of an element which by its very nature is distributed. The Constant Phase Element (CPE) meets such a requirement. It has the form P = Y0 wn... 

The actual adsorption of vapor molecules takes place mainly on the surface of internal passages within the adsorbent particles, since that is where most of the available surface exists. The adsorption process may be either physical or chemical in nature. Physical adsorption is a readily reversible process that occurs as a result of the physical attraction between the gas molecules and the molecules of the solid surface. If the gas-solid intermolecular attraction is greater than the intermolecular attractions in the gas phase, the gas will condense on the solid surface, even though its pressure is lower than its vapor pressure at the prevailing temperature. For example, the equilibrium adsorption pressure of acetone on activated carbon may, under some conditions, be as little as 150 to 1,100 of the equilibrium vapor pressure at... 

Claims of commercial manufacturers notwithstanding, it is evident that pheromones do not function as behavioural releasers in humans in the same way as they do in other species. Instead of searching for specific reactions to purported human pheromones, it may be that these chemicals are better described as modulators (Jacob and McClintock 2000) which influence psychological states and, thereby, also influence behaviour in a variety of fashions depending on the situation in which they are experienced, or the accompanying cues. The co-occurrence of different cues can affect their interpretation (Rowe 1999). In humans, we know that odour cues provide non-redundant information about potential mates because, while both visual and olfactory cues may be used to gauge physical attractiveness, the information in each is not equivalent (Roberts, Little, Gosling, Jones, Perrett, Carter and Petrie 2005). 

Black, S. L. and Biron, C. (1982) Androstenol as a human pheromone No effect on perceived physical attractiveness. Behav. Neural Biol. 34, 326-330. 

A) Anesthetics are physically attracted to the aqueous phase of neuronal membranes. 

There is an imbalance of molecular forces at the interface between two phases. This is caused by physical attraction between molecules. This imbalance of forces is known as interfacial tension. 

It can therefore be stated generally that the odor of any perfumed product is affected by the product base in two ways (1) by the odor of the base itself and (2) by the way the base, through physical attraction forces, affects the odor of the perfume. Sometimes a third factor, chemical decomposition of the perfume by components of the base, enters the picture. This will be considered later. 

Water adsorbs into the walls of a glass container, but that adsorption is the extent of its adhesion. Some adsorbed molecules react chemically with some types of containers in a process called chemical adsorption (chemisorption. For example, carbon monoxide chemisorbs with palladium, but not with gold). The bonds resulting from chemisorption can hold molecules to the surface with far greater force than would exist with only physical attraction. It is also possible for a molecule (that normally would not chemisorb with the container wall) to break up when hitting the wall s surface. At that point the molecule s constituent parts chemisorb with the container walls. When an adsorbed gas reacts with the materials of a container, it is called reconstruction (for example, the reconstruction of iron with oxygen is rust). 

Over the last decade, the poor economics of new polymer and copolymer production and the need for new materials whose performance/ cost ratios can be closely matched to specific applications have forced polymer researchers to seriously consider purely physical polymer blend systems. This approach has been comparatively slow to develop, however, because most physical blends of different high molecular weight polymers prove to be immiscible. That is, when mixed together, the blend components are likely to separate into phases containing predominantly their own kind. This characteristic, combined with the often low physical attraction forces across the immiscible phase boundaries, usually causes immiscible blend systems to have poorer mechanical properties than could be achieved by the copolymerization route. Despite this difficulty a number of physical blend systems have been commercialized, and some of these are discussed in a later section. Also, the level of technical activity in the physical blend area remains high, as indicated by the number of reviews published recently (1-10). 

Equation 4.26, as noted above, has two terms—a chemical complexation term, [-SM(m 1)[H+]/[-SHj[Mm+], and an electrical potential term, exp[(m-l)A /// T]. The electrical potential term is directly dependent on pH (see Eq. 4.27b). Therefore, by regulating the magnitude of the physical attraction between a metal and a surface, the electrical potential indirectly affects the magnitude of surface complexes that could form. Recall that before a chemical complex or inner-sphere complex between two reactants is formed, they must physically collide successfully at a given frequency. When a metal-ion (e.g., contaminant) and a surface are oppositely charged, physical collisions maximize, and, thus, inner-sphere complex formation maximizes. When a metal-ion (e.g., contaminant) and a surface are similarly charged, physical collisions minimize, and inner-sphere complex formation also minimizes. 

An adhesive is a material capable of holding together solid materials by means of surface attachment. Adhesion is the physical attraction of the surface of one material for the surface of another. An adherend is the solid material to which the adhesive adheres and the adhesive bond or adhesive joint is the assembly made by joining adlierends together by means of an adhesive. Practical adhesion is the physical strength of an adhesive bond It primarily depends on the forces of adhesion, but its magnitude is determined by the physical properties of the adhesive and the adherend, as well as the engineering of the adhesive bond. 

Our results for the Friedel-Crafts acylation of coal (7) indicate that bituminous coal becomes extractable not only by depolymerization but also by the Introduction of long chain substituents into the coal molecules. By the substitution with long chain aliphatic groups, the separation between the aromatic structures of adjacent molecules can be Increased so that the physical attractive forces are reduced. We tried alkylation In order to make bituminous coal more extractable. Possibly In the future extracts can be obtained economically by reaction of coal with mineral oil fractions under relatively mild conditions. 

The immobilization of biomolecules on solid surfaces offers considerable advantages to enzymes in solution. Immobilization via physical attraction is often not reliable because of problems concerning leaching and loss of the biomolecule [1]. Therefore, covalent attachment of the enzymes to solid surfaces is advantageous, especially in biotechnology, where the biomolecule should be separated fix)m the reaction mixture, or for the construction of biosensors, where a biocatalyst would be used in a detector system. 

For neutral molecules, the simplest and normally the strongest direct electrostatic force is tliat operating between two permanent dipoles. This force can dominate "physical" attractive interactions if the molecules have high effective polarity, i.e., if they are small and liave large pemianent dipoles. 

The intermolecular forces which come into play in the orientated or crystalline regions are of three kinds. The most powerful are the chemical linkages, then the phenomenon known as hydrogen bonding, and finally the rather ill-defined physical attraction known as Van der Waals forces. The effect of these forces, which will be proportional to the degree of orientation, is shown in Table 2.2. 

The seven individuals in the small cluster have more positive values and relatively low 5 N ratios. This group was eating largely terrestrial, foods in childhood. Moreover, all seven of these individuals had similarly modified front teeth, flaked and filed to produce a pointed appearance (Fig. 7.17). This cultural practice is well known from Africa and was thought to enhance one s physical attractiveness. This pattern of modification is known to have been practiced in Mozambique. These seven distinctive individuals were very likely bom in Mozambique and brought to Cape Town as slaves. On the other hand, four out of five of the Type C burials have very negative values, and appear as outliers on the left-hand side of the graph. Their diets were based on C, plants from temperate environments. 

Hygroscopic material—solids having an affinity for liquids due to a chemical or physical attraction between the solids and the liquid. 

Based on weak physical attraction sensitive to temperature, nonspecific, rapid (no activation barrier), possibly multilayer AH os < AHvap ... 

The use of Slater-type orbitals as basis functions is currently feasible only for atoms, diatomics and, with effort, linear polyatomic molecules. However, research into more powerful methods continues and the physical attractiveness of these functions is such that the development of effective integral evaluation methods would be a major breakthrough in quantum chemistry. 

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