scholarly journals Subunit treadmilling of microtubules or actin in the presence of cellular barriers: possible conversion of chemical free energy into mechanical work.

1982 ◽  
Vol 79 (2) ◽  
pp. 490-494 ◽  
Author(s):  
T. L. Hill ◽  
M. W. Kirschner
Keyword(s):  
Free Energy ◽  
Mechanical Work ◽  
Chemical Free Energy

scholarly journals Remodeler Catalyzed Nucleosome Repositioning: Influence of Structure and Stability

2020 ◽  
Vol 22 (1) ◽  
pp. 76
Author(s):  
Aaron Morgan ◽  
Sarah LeGresley ◽  
Christopher Fischer
Keyword(s):  
Free Energy ◽  
Dna Replication ◽  
Recent Work ◽  
Chromatin Remodeling ◽  
Chromatin Structure ◽  
Genetic Information ◽  
Molecular Machines ◽  
Mechanical Work ◽  
Eukaryotic Genome ◽  
Hydrolysis Of

The packaging of the eukaryotic genome into chromatin regulates the storage of genetic information, including the access of the cell’s DNA metabolism machinery. Indeed, since the processes of DNA replication, translation, and repair require access to the underlying DNA, several mechanisms, both active and passive, have evolved by which chromatin structure can be regulated and modified. One mechanism relies upon the function of chromatin remodeling enzymes which couple the free energy obtained from the binding and hydrolysis of ATP to the mechanical work of repositioning and rearranging nucleosomes. Here, we review recent work on the nucleosome mobilization activity of this essential family of molecular machines.

Estimation of the System Free Energy of the Lath Martensite Phase in High Cr Ferritic Steels

2006 ◽  
Vol 15-17 ◽  
pp. 690-695 ◽  
Author(s):  
Tomonori Kunieda ◽  
Kensuke Akada ◽  
Yoshinori Murata ◽  
Toshiyuki Koyama ◽  
Masahiko Morinaga
Keyword(s):  
Free Energy ◽  
Ternary Alloy ◽  
Elastic Strain ◽  
Lath Martensite ◽  
Elastic Strain Energy ◽  
Martensite Phase ◽  
Interfacial Energies ◽  
Martensite Packet ◽  
Chemical Free Energy ◽  
Martensite Microstructure

The system free energy was estimated for the martensite phase of an Fe-Cr-C ternary alloy, 12Cr2W and 12Cr2W0.5Re steels. The system free energy of the martensite phase is defined as, Gsys = G0 + Estr + Esurf , where G0 is the chemical free energy, Esurf is the interfacial energy for the boundaries in the martensite microstructure, and Estr is the elastic strain energy due to the dislocations in the martensite phase. From the experimental results on SEM/EBSD, the total interfacial energies were estimated to be 0.83J/mol for the ternary alloy and 4.8J/mol for both 12Cr2W and 12Cr2W0.5Re steels in the as-quenched state. Also, the elastic strain energies were estimated to be 7.1J/mol for the ternary alloy, 9.6J/mol for 12Cr2W steel and 9.8J/mol for 12Cr2W0.5Re steel in the as-quenched state. So, the system free energy was about 7.9J/mol for ternary alloy. On the other hand, the system free energy was about 14.4J/mol for 12Cr2W steel and 14.6J/mol for 12Cr2W0.5Re steel. So, these microstructural energies operate as a driving force for the microstructure evolution, e.g., recovery of dislocations and the coarsening of the sub-structures such as martensite-packet, -block and -lath.

Two-Phase Microstructures Formed by Phase-Separation of Coherent Precipitates in Elastically Constrained Alloy Systems

2010 ◽  
Vol 638-642 ◽  
pp. 2215-2220 ◽  
Author(s):  
Minoru Doi
Keyword(s):  
Free Energy ◽  
Phase Separation ◽  
Surface Energy ◽  
Phase Region ◽  
Precipitate Phase ◽  
Two Phase ◽  
Phase Separations ◽  
Chemical Free Energy ◽  
Elastic Constraint ◽  
Alloy Systems

Coherent two-phase microstructures consisting of ordered precipitate and disordered matrix phases sometimes exhibit a phase-separation, which brings the split and/or the decelerated coarsening of precipitates. When the coherent two-phase microstructure of A1+L12 (+’) in Ni-base alloys are aged inside the two-phase region of A1+L12 , the L12 precipitate sometimes exhibit a phase-separation and A1 phase newly appears and grows in each L12 precipitate. Phase-separations of the same type to the above also take place due to ageing of coherent two-phase microstructures of A2+D03 and A2+B2 in Fe-base alloys: D03 and B2 precipitates sometimes exhibit phase-separations and A2 phase newly appears and grows in both precipitates. These types of phase-separation take place under the influence of chemical free energy. In the course of further ageing, the new disordered phases of A1 and A2 change their morphology in various ways depending on the elastic constraint: i.e. the morphology of new A1 or A2 phase is influenced by the elastic energies and the surface energy.

The role of chemical free energy and elastic strain in the nucleation of zirconium hydride

2013 ◽  
Vol 441 (1-3) ◽  
pp. 395-401 ◽  
Author(s):  
A.T.W. Barrow ◽  
C. Toffolon-Masclet ◽  
J. Almer ◽  
M.R. Daymond
Keyword(s):  
Free Energy ◽  
Elastic Strain ◽  
Zirconium Hydride ◽  
Chemical Free Energy

scholarly journals Measurements of to Temperatures of Supersaturated Si-As Alloys

1990 ◽  
Vol 205 ◽  
Author(s):  
Kwang-Ryeol Lee ◽  
Jeffrey A. West ◽  
Patrick M. Smith ◽  
M. J. Aziz ◽  
J. A. Knapp
Keyword(s):  
Free Energy ◽  
Pulsed Laser ◽  
Congruent Melting ◽  
Laser Melting ◽  
Concentration Region ◽  
Energy Functions ◽  
Congruent Melting Point ◽  
Liquid Phases ◽  
Chemical Free Energy ◽  
Beam Technique

AbstractThe congruent melting point, or To curve, of crystalline Si-As alloys has been measured in the range of 1.6 to 18.1 at. % arsenic by line source electron beam annealing. Alloys were created by ion implantation of As into 0.1mm Si-on-sapphire and crystallized by pulsed laser melting. To temperatures decrease from 1673±10K at 2.0 at.% As to 1516±30K at 18.1 at.% As. The results of these measurements are significantly higher than the previous results of studies using pulsed laser melting techniques. Advantages of the e-beam technique over previous techniques are discussed. Chemical free energy functions of the solid and liquid phases were calculated from existing thermodynamic data. The calculated To curve agrees with the measured values only in low concentration region (less than 8 at.%).

On the Chemical Free Energy of the Electrical Double Layer

Langmuir ◽  
2003 ◽  
Vol 19 (4) ◽  
pp. 1114-1120 ◽  
Author(s):  
Marian Manciu ◽  
Eli Ruckenstein
Keyword(s):  
Free Energy ◽  
Double Layer ◽  
Electrical Double Layer ◽  
Chemical Free Energy

Effect of Extrusion Pass on Microstructure and Transformation Temperature of NiTiNb Alloy

2014 ◽  
Vol 687-691 ◽  
pp. 4347-4350
Author(s):  
Jun Wei Liu ◽  
Zi Peng Ouyang ◽  
Shi Qiang Lu ◽  
Jian Bao Hou ◽  
Yuan Zhi Huang
Keyword(s):  
Free Energy ◽  
Interfacial Energy ◽  
Transformation Temperature ◽  
Energy Transformation ◽  
Transformation Temperatures ◽  
Chemical Free Energy

In this research, the Effect of extrusion pass on microstructure and transformation temperature of NiTiNb alloy was researched. The results shows that ECAP can efficiently break the hard and brittle (Ti, Nb)2Ni phase. At the same time, β-Nb phase particles were precipitated and grow up after ECAP process.Due to enhancement of interfacial energy, train energy and non-chemical free energy, transformation temperatures including: As, Af, Ms and Mf increases with extrusion pass.

scholarly journals A chemo-mechanical free-energy-based approach to model durotaxis and extracellular stiffness-dependent contraction and polarization of cells

2016 ◽  
Vol 6 (1) ◽  
pp. 20150067 ◽  
Author(s):  
Vivek B. Shenoy ◽  
Hailong Wang ◽  
Xiao Wang
Keyword(s):  
Free Energy ◽  
Molecular Motors ◽  
Mechanical Energy ◽  
Second Law Of Thermodynamics ◽  
Mechanical Coupling ◽  
Coupling Parameters ◽  
Chemical Free Energy ◽  
Myosin Motors ◽  
Stress Dependent ◽  
Extracellular Environment

We propose a chemo-mechanical model based on stress-dependent recruitment of myosin motors to describe how the contractility, polarization and strain in cells vary with the stiffness of their surroundings and their shape. A contractility tensor, which depends on the distribution of myosin motors, is introduced to describe the chemical free energy of the cell due to myosin recruitment. We explicitly include the contributions to the free energy that arise from mechanosensitive signalling pathways (such as the SFX, Rho-Rock and MLCK pathways) through chemo-mechanical coupling parameters. Taking the variations of the total free energy, which consists of the chemical and mechanical components, in accordance with the second law of thermodynamics provides equations for the temporal evolution of the active stress and the contractility tensor. Following this approach, we are able to recover the well-known Hill relation for active stresses, based on the fundamental principles of irreversible thermodynamics rather than phenomenology. We have numerically implemented our free energy-based approach to model spatial distribution of strain and contractility in (i) cells supported by flexible microposts, (ii) cells on two-dimensional substrates, and (iii) cells in three-dimensional matrices. We demonstrate how the polarization of the cells and the orientation of stress fibres can be deduced from the eigenvalues and eigenvectors of the contractility tensor. Our calculations suggest that the chemical free energy of the cell decreases with the stiffness of the extracellular environment as the cytoskeleton polarizes in response to stress-dependent recruitment of molecular motors. The mechanical energy, which includes the strain energy and motor potential energy, however, increases with stiffness, but the overall energy is lower for cells in stiffer environments. This provides a thermodynamic basis for durotaxis, whereby cells preferentially migrate towards stiffer regions of the extracellular environment. Our models also explain, from an energetic perspective, why the shape of the cells can change in response to stiffness of the surroundings. The effect of the stiffness of the nucleus on its shape and the orientation of the stress fibres is also studied for all the above geometries. Along with making testable predictions, we have estimated the magnitudes of the chemo-mechanical coupling parameters for myofibroblasts based on data reported in the literature.

Sign in / Sign up

Export Citation Format

Share Document