Polarity and gradients in lepidopteran wing epidermis

Development ◽  
1976 ◽  
Vol 36 (3) ◽  
pp. 489-512
Author(s):  
James B. Nardi ◽  
Fotis C. Kafatos
Keyword(s):  
Free Energy ◽  
Minimum Free Energy ◽  
Alternative Interpretation ◽  
Original Position ◽  
Cell Contact ◽  
Two Dimensional ◽  
Free Energies ◽  
Minimal Cell ◽  
Final Size ◽  
Cell Densities

For explaining the Manduca wing gradient (Nardi & Kafatos, 1976) a model which postulates a proximo-distal gradient in cellular adhesiveness is considered. The model is based on Steinberg's (1963) differential adhesiveness hypothesis. Rosette formation in certain trans-posed and/or reoriented grafts can be adequately explained by this model. Several predictions, formulated by using the concept of surface free energy as a thermodynamic measure of adhesiveness, have been tested and proven correct. (1) Transposed grafts tend to assume circular forms, which are configurations of minimum free energy. (2) Because of the pressure difference expected across the interface of two cell populations with different surface free energies, cell densities increase in both distally and proximally transposed grafts. As a corollary to this rule, final size of a graft is a function of its distance from the original position.(3) Histological sections of host-graft boundaries suggest minimal cell contact at the interface. In proximal grafts placed in distal regions, cell density is far lower near the host-graft inter face, as compared to the high interior density; the peripheries of distal grafts do not show this effect. (4) Juxtaposition of three different wing regions in all possible arrangements yields the expected two-dimensional configurations. (5) Differences in adhesiveness can be demonstrated by allowing two different wing grafts to interact in an essentially neutral environment (i.e. at a leg or antenna site). As the distance between two given graft regions increases, the extent of their final contact decreases. When applied to other insect systems, the model not only offers an alternative interpretation for results currently explained by diffusible substance models, but also accounts for certain features that were unexplained by other models.

scholarly journals Calculating solution redox free energies withab initioquantum mechanical/molecular mechanical minimum free energy path method

2009 ◽  
Vol 130 (16) ◽  
pp. 164111 ◽  
Author(s):  
Xiancheng Zeng ◽  
Hao Hu ◽  
Xiangqian Hu ◽  
Weitao Yang
Keyword(s):  
Free Energy ◽  
Minimum Free Energy ◽  
Free Energies

Effect of the brachypod mutation on cell adhesion and chondrogenesis in aggregates of mouse limb mesenchyme

Development ◽  
1977 ◽  
Vol 42 (1) ◽  
pp. 209-217
Author(s):  
Jackie Duke ◽  
William A. Elmer
Keyword(s):  
Cell Adhesion ◽  
Single Cells ◽  
The Other ◽  
Cell Contact ◽  
Final Size ◽  
Limb Mesenchyme ◽  
Mouse Limb ◽  
Rotation Culture ◽  
Cell Densities ◽  
Rate Of Decline

Twelve-day normal and brachypod mouse limb mesenchyme was studied in rotation culture. Over a 3½ h period the rate of decline of single cells was significantly greater in mutant than in normal cultures, probably because the brachypod cells were more adhesive. However, the final size of the aggregates and their cell densities were the same by 24 h of incubation. On the other hand their pattern of chondrogenesis was different. Normal aggregates contained condensations with typical histotypic cartilage by 24 h of incubation, and were entirely chondrifled by 4 days in culture. The condensations in brachypod aggregates were fewer, smaller, and delayed in their chondrogenesis. Never more than 50% of the brachypod aggregate exhibited chondrogenesis. The importance of cell contact and cell density to the chondrogenic process are discussed.

scholarly journals Second-order approximation for heat conduction: dissipation principle and free energies

2016 ◽  
Vol 472 (2186) ◽  
pp. 20150707 ◽  
Author(s):  
Giovambattista Amendola ◽  
Mauro Fabrizio ◽  
Murrough Golden ◽  
Barbara Lazzari
Keyword(s):  
Free Energy ◽  
Heat Conduction ◽  
Order Approximation ◽  
Minimum Free Energy ◽  
Second Order ◽  
Fading Memory ◽  
Free Energies ◽  
Second Order Approximation ◽  
Energy Functionals ◽  
With Memory

In the context of new models of heat conduction, the second-order approximation of Tzou's theory, derived by Quintanilla and Racke, has been studied recently by two of the present authors, where it was proved equivalent to a fading memory material. The importance of determining free energy functionals for such materials, and indeed for any material with memory, is emphasized. Because the kernel does not satisfy certain convexity restrictions that allow us to obtain various traditional free energies for materials with fading memory, it is necessary to restrict the study to the minimum and related free energies, which do not require these restrictions. Thus, the major part of this work is devoted to deriving an explicit expression for the minimum free energy. Simple modifications of this expression also give an intermediate free energy and the maximum free energy for the material. These derivations differ in certain important respects from earlier work on such free energies.

scholarly journals Free energies in a general non-local theory of a material with memory

2014 ◽  
Vol 24 (06) ◽  
pp. 1037-1090 ◽  
Author(s):  
Giovambattista Amendola ◽  
Mauro Fabrizio ◽  
John Murrough Golden
Keyword(s):  
Free Energy ◽  
General Theory ◽  
Constitutive Equations ◽  
Minimum Free Energy ◽  
Local Theory ◽  
Free Energies ◽  
Non Local ◽  
Local Materials ◽  
With Memory ◽  
Simple Materials

A general theory of non-local materials, with linear constitutive equations and memory effects, is developed within a thermodynamic framework. Several free energy and dissipation functionals are constructed and explored. These include an expression for the minimum free energy and a functional that is a free energy for important categories of memory kernels and is explicitly a functional of the minimal state. The functionals discussed have a similar general form to the corresponding expressions for simple materials. A number of new results are derived for them, most of which apply equally to both types of material. In particular, detailed formulae are given for these quantities in the case of sinusoidal histories.

SAMPL6 Octanol-Water Partition Coefficients from Alchemical Free Energy Calculations with MBIS Atomic Charges

2019 ◽  
Author(s):  
Maximiliano Riquelme ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Free Energy ◽  
Electron Density ◽  
Free Energy Calculations ◽  
Basis Set ◽  
Energetic Cost ◽  
Atomic Charges ◽  
Free Energies ◽  
Energy Calculations ◽  
Alchemical Free Energy ◽  
Alchemical Free Energy Calculations

In molecular modeling the description of the interactions between molecules forms the basis for a correct prediction of macroscopic observables. Here, we derive atomic charges from the implicitly polarized electron density of eleven molecules in the SAMPL6 challenge using the Hirshfeld-I and Minimal Basis Set Iterative Stockholder(MBIS) partitioning method. These atomic charges combined with other parameters in the GAFF force field and different water/octanol models were then used in alchemical free energy calculations to obtain hydration and solvation free energies, which after correction for the polarization cost, result in the blind prediction of the partition coefficient. From the tested partitioning methods and water models the S-MBIS atomic charges with the TIP3P water model presented the smallest deviation from the experiment. Conformational dependence of the free energies and the energetic cost associated with the polarization of the electron density are discussed.

Molecular orientation of liquid aliphatic hydrocarbons on the surface and at the interface with water

1989 ◽  
Vol 54 (12) ◽  
pp. 3171-3186 ◽  
Author(s):  
Jan Kloubek
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Molecular Orientation ◽  
Phase Changes ◽  
Aliphatic Hydrocarbons ◽  
Water Molecules ◽  
Free Energies ◽  
Dispersion Component ◽  
System Water ◽  
Orientation Of Molecules

The validity of the Fowkes theory for the interaction of dispersion forces at interfaces was inspected for the system water-aliphatic hydrocarbons with 5 to 16 C atoms. The obtained results lead to the conclusion that the hydrocarbon molecules cannot lie in a parallel position or be randomly arranged on the surface but that orientation of molecules increases there the ration of CH3 to CH2 groups with respect to that in the bulk. This ratio is changed at the interface with water so that the surface free energy of the hydrocarbon, γH, rises to a higher value, γ’H, which is effective in the interaction with water molecules. Not only the orientation of molecules depends on the adjoining phase and on the temperature but also the density of hydrocarbons on the surface of the liquid phase changes. It is lower than in the bulk and at the interface with water. Moreover, the volume occupied by the CH3 group increases on the surface more than that of the CH2 group. The dispersion component of the surface free energy of water, γdW = 19.09 mJ/m2, the non-dispersion component, γnW = 53.66 mJ/m2, and the surface free energies of the CH2 and CH3 groups, γ(CH2) = 32.94 mJ/m2 and γ(CH3) = 15.87 mJ/m2, were determined at 20 °C. The dependence of these values on the temperature in the range 15-40 °C was also evaluated.

Chemical equilibrium and chemical kinetics

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Chemical Kinetics ◽  
Chemical Equilibrium ◽  
First Principles ◽  
Effect Of Temperature ◽  
Total System ◽  
Free Energies

Building on the previous chapter, this chapter examines gas phase chemical equilibrium, and the equilibrium constant. This chapter takes a rigorous, yet very clear, ‘first principles’ approach, expressing the total Gibbs free energy of a reaction mixture at any time as the sum of the instantaneous Gibbs free energies of each component, as expressed in terms of the extent-of-reaction. The equilibrium reaction mixture is then defined as the point at which the total system Gibbs free energy is a minimum, from which concepts such as the equilibrium constant emerge. The chapter also explores the temperature dependence of equilibrium, this being one example of Le Chatelier’s principle. Finally, the chapter links thermodynamics to chemical kinetics by showing how the equilibrium constant is the ratio of the forward and backward rate constants. We also introduce the Arrhenius equation, closing with a discussion of the overall effect of temperature on chemical equilibrium.

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