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Micro entropy

The vectors of Bf express f in the original basis h, see Eqs. (28-29). To prepare for a discussion of proton tunnelling in DNA we will briefly deliberate on the concept of the micro entropy. A direct generalisation of Gibbs entropy follows from the definition below (Coleman s normalisation [27])... [Pg.133]

Note that the Gibb s partition of the micro entropy above is not maximum for a near equilibrium situation. This follows from the fact that the function -xlnx 0 < x < 1, has a maximum for x = /e. Assuming that our correlation model in a more realistic dissipative system of varying occurrence of base pairs would prefer a "close to equilibrium" entropy, we find that a recalculation of our parameters above yields the trend... [Pg.136]

McBride, M.C. (1985) Influence of glycine on Cu adsorption by micro crystalline gibbsite and goethite. Clays Clay Min. 33 397-402 McCafferty, E. Zettlemoyer, A.C. (1970) Entropy of adsorption and the mobility of water vapor on a- Fe20. J. Colloid Interface Sci. 34 452-460... [Pg.606]

Two papers reported powder pattern crystallographic results. The paper by Santos et al. (7) stood out from the rest because it presented a collection of more classical physical chemistry experiments. In this paper the authors described the use of micro-combustion calorimetry, Knudsen effusion to determine enthalpy of sublimation, differential scanning calorimetry, X-ray diffraction, and computed entropies. While this paper may provide some justification for including bomb calorimetry and Knudsen cell experiments in student laboratories, the use of differential scanning calorimetry and x-ray diffraction also are alternatives that would make for a crowded curriculum. Thus, how can we choose content for the first physical chemistiy course that shows the currency of the discipline while maintaining the goal to teach the fundamentals and standard techniques as well ... [Pg.178]

Here, AH(A-B) is the partial molar net adsorption enthalpy associated with the transformation of 1 mol of the pure metal A in its standard state into the state of zero coverage on the surface of the electrode material B, ASVjbr is the difference in the vibrational entropies in the above states, n is the number of electrons involved in the electrode process, F the Faraday constant, and Am the surface of 1 mol of A as a mono layer on the electrode metal B [70]. For the calculation of the thermodynamic functions in (12), a number of models were used in [70] and calculations were performed for Ni-, Cu-, Pd-, Ag-, Pt-, and Au-electrodes and the micro components Hg, Tl, Pb, Bi, and Po, confirming the decisive influence of the choice of the electrode material on the deposition potential. For Pd and Pt, particularly large, positive values of E5o% were calculated, larger than the standard electrode potentials tabulated for these elements. This makes these electrode materials the prime choice for practical applications. An application of the same model to the superheavy elements still needs to be done, but one can anticipate that the preference for Pd and Pt will persist. The latter are metals in which, due to the formation of the metallic bond, almost or completely filled d orbitals are broken up, such that these metals tend in an extreme way towards the formation of intermetallic compounds with sp-metals. The perspective is to make use of the Pd or Pt in form of a tape on which the tracer activities are electrodeposited and the deposition zone is subsequently stepped between pairs of Si detectors for a-spectroscopy and SF measurements. [Pg.197]

So far the micro-mechanical origin of the Mullins effect is not totally understood [26, 36, 61]. Beside the action of the entropy elastic polymer network that is quite well understood on a molecular-statistical basis [24, 62], the impact of filler particles on stress-strain properties is of high importance. On the one hand the addition of hard filler particles leads to a stiffening of the rubber matrix that can be described by a hydrodynamic strain amplification factor [22, 63-65]. On the other, the constraints introduced into the system by filler-polymer bonds result in a decreased network entropy. Accordingly, the free energy that equals the negative entropy times the temperature increases linear with the effective number of network junctions [64-67]. A further effect is obtained from the formation of filler clusters or a... [Pg.6]

Van t Hoff plots may be used to compare the entropies of solute transfer, AS, between mobile and stationary phases in CEC and (pressure-driven) micro-HPLC on the same column. Djordjevic et al. found [57] that AS was more negative for electrodrive, a difference attributed to Joule heating, which was thought to bring about differences between set and actual column temperatures. [Pg.183]

When A is very surface active, it is called a co-surfactant. Under appropriate conditions, mixtures of surfactant and co-surfactants can give rise to Interfacial tensions that are so low that the Gibbs energy of increasing the area can be outweighed by the entropy gain of forming new droplets. This is the basis for the formation of micro-emulsions, which we shall not further consider here. [Pg.531]

The crystallization of a liquid is a change of phase in which symmetry is broken a spatially periodic state arises from one that was invariant under translations. A full description of such a phase change would involve three components (1) an understanding of the equilibrium aspects of the transition (at what temperature and pressure it takes place, what changes in thermodynamic properties such as volume and entropy accompany it), (2) a micro-... [Pg.263]

Generally speaking, the degrees of freedom in many-body systems, such as Ar7, are too many to analyze the phase-space dynamics, and only limited methods originally developed to investigate chaotic systems with a few degrees of freedom can be applicable for the analysis. Seko et al. calculated the phase volume—that is, the configuration entropy—of Ar7 and proposed a new concept of the temperature in micro-clusters based on this phase volume [17], A phase-space analysis seems to be prospective even for many-body systems, such as Ar7. However, most of the currently available methods concern statistical properties. The methods and quantities that are directly related to the dynamics are expected for a detailed analysis. [Pg.130]

The importance of FIPI is twofold. It can be used to promote phase inversion without changing the thermodynamics of the system to obtain a higher entropy state, or it is possible to delay phase inversion while reducing the system entropy. The characteristics of the microstructure formed (such as emulsion droplet size) are dependent on the type of microstructure and deformation (shear, extension, or combined), as well as the deformation rate. To maximize the fluid micro-structure/flow field interactions, the flow fleld must be uniform, which requires the application of the flow field over a small processing volume, which can be achieved by using MFCS mixers or CDDMs. [Pg.189]

In a number of publications [12], classification of phase transitions in small systems has been presented. This scheme is based on the distribution of zeroes of the canonical partition function in the complex temperature plane. Among others. Gross has suggested a microcanonical treatment [13], where phase transitions of different order are distinguished by the curvature of the entropy 5 = In According to this scheme, a back-bending in the micro-... [Pg.133]

The HLD concept has been recently related to the so-called net-average curvature which indicates the size of the oil and water domains in the micro emulsion. For marginal microemulsions, i.e. of the WI or WII type at some distance from optimum, the inverse of the swollen micelle Sauter diameter is proportional to HLD. The zero net curvature at optimum does not result from infinite radius but rather from the coexistence of finite curvatures of opposite signs. For bicontinuous micro emulsions, it is the inverse of the characteristic length which is maximised at HLD = 0. As discussed elsewhere [38], its value at optimum formulation is the maximum distance that a molecule of oil or water can be separated from the surfactant layer and still interacts with it. In other words, it is the length at which the molecular interaction becomes equal to the molecular entropy. [Pg.104]

A direct connection between the MC probability function and the micro-canonical entropy of the system is realized in the ESMC algorithm [17]. The condition for a uniform (or flat) probability distribution of energy in a Metropolis-type MC algorithm can be expressed as... [Pg.250]

It was decided to measure the integral heats of adsorption micro-calorimetrically, free energies of adsorption by a Gibbs integration of the adsorption isotherms, and integral entropies by numerical difference. Though the results of this survey may be incomplete, they have provided some insight into the specificity of physical adsorption processes. [Pg.222]

Free Radical Self-Termination. The cage efficiencies and activation parameters for the phenylthiyl collisional cage pair provide the basis for illustrating some of the important features of equations (3)-(5) and for predicting the observed rates of self-termination of phenylthiyl free radicals. Application of the SW procedure to the completely diffusion controlled step of Scheme 1 (kj) ) for phenylthiyl free radicals in cis-decalin can be expressed by the transition state equation with a AH d of 3448 cal/mole and a AS d of -4.3 cal/mole-K. The corresponding activation enthalpy (AH d) from the Stokes-Einstein-Schmoluchowski relationship is 3685 cal/mole for cis-decalin) so that the a of equation (8) is 0.94. The micro-frictional multiplier (mf, equation 8 above), which is incorporated into the SW activation entropy (AS j)), is 2.4. The SW activation entropy for a truly diffusion controlled self-termination of phenylthiyl free radicals (2k obs -2kj), - 1 at... [Pg.121]


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See also in sourсe #XX -- [ Pg.133 ]




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