Phase Transitions of a Two-Dimensional Periodic Hydrophilic Hydrophobic Chain

1998 ◽  
Vol 09 (08) ◽  
pp. 1459-1468 ◽  
Author(s):  
Enzo Orlandini ◽  
Thomas Garel
Keyword(s):  
Phase Separation ◽  
Ground State ◽  
Square Lattice ◽  
Hydrophobic Core ◽  
Periodic Distribution ◽  
Hydrophobic Polymer ◽  
Markov Chain Method ◽  
Hydrophobic Chain ◽  
A Chain ◽  
Chain Lengths

We study a single self-avoiding hydrophilic hydrophobic polymer chain, through Monte Carlo lattice simulations. The affinity of monomer i for water is characterized by a (scalar) charge λi, and the monomer-water interaction is short-ranged. Assuming incompressibility yields an effective short ranged interaction between monomer pairs (i,j), proportional to (λi + λj). In this article, we take λi=+1 (resp. (λi=-1)) for hydrophilic (resp. hydrophobic) monomers and consider a chain with (i) an equal number of hydrophilic and -phobic monomers (ii) a periodic distribution of the λi along the chain, with periodicity 2p. This model may be of interest in various situations (protein folding, polysoaps, …) The simulations are done on the square lattice (d=2), for various chain lengths N. There is a critical value (pc(N)~0.07N) of the periodicity, which distinguishes between different low temperature structures. For p>pc, the ground state corresponds to a macroscopic phase separation between a dense hydrophobic core and hydrophilic loops. For p<pc (but not too small), one gets a microscopic (finite scale) phase separation, and the ground state corresponds to a chain or network of hydrophobic droplets, coated by hydrophilic monomers. These different cases will be explored through a Multiple Markov chain method. The results for the d=3 case (where pc(N)~N1/3) are similar.

Phase Separation Due to Nearest Neighbor Attractive Interactions in a Two-Dimensional Model

2003 ◽  
Vol 17 (16) ◽  
pp. 853-861 ◽  
Author(s):  
M. Shaw ◽  
W. P. Su
Keyword(s):  
Phase Separation ◽  
Long Range ◽  
Ground State ◽  
Quantum Monte Carlo ◽  
Nearest Neighbor ◽  
Square Lattice ◽  
Correlation Effects ◽  
Dimensional Model ◽  
Long Range Correlations ◽  
Half Filling

We have studied a correlated fermion model with nearest neighbor attractive interactions on a square lattice by means of quantum Monte Carlo simulation. At half-filling this model exhibits rather strong correlation effects. Charge fluctuations are suppressed and the ground state is an insulator with long-range anitferromagnetic correlations. When doped with holes this model exihibits phase separation which seems to be triggered by the antiferromagnetic long-range correlations.

Spin-Singlet Ground State in Two-Dimensional S=1/2 Frustrated Square Lattice: (CuCl)LaNb2O7

2005 ◽  
Vol 74 (6) ◽  
pp. 1702-1705 ◽  
Author(s):  
H. Kageyama ◽  
T. Kitano ◽  
N. Oba ◽  
M. Nishi ◽  
S. Nagai ◽  
...  
Keyword(s):  
Ground State ◽  
Square Lattice ◽  
Singlet Ground State ◽  
Two Dimensional ◽  
Spin Singlet

scholarly journals Optimal electronic doping in p-wave superconductors

2021 ◽  
Vol 67 (6 Nov-Dec) ◽  
Author(s):  
Benjamín Millan ◽  
Ivonne Judith Hernández ◽  
Luis Antonio Pérez ◽  
José Samuel Millan
Keyword(s):  
Critical Temperature ◽  
Ground State Energy ◽  
Electron Concentration ◽  
Ground State ◽  
State Energy ◽  
P Wave ◽  
Square Lattice ◽  
S Wave ◽  
Optimal Doping ◽  
D Wave

Recently, within a generalized Hubbard model which includes correlated nearest (∆t) and next-nearest hopping interactions (∆t_3 ), a comparative study between d- and s*- wave superconducting ground states on a square lattice was performed. It was found that the critical temperature of transition T_c (n), as a function of the electron concentration n, reaches a maximum (T_(c-max) at a given optimal doping (n_op) for each value of the ratio (t’)⁄t, where t and t’ are the tight-binding nearest and next-nearest hopping parameter of a square lattice, respectively. From all values obtained for T_(c-max) ((t’)⁄(t,n_op) a global minimum one was encountered for both symmetries. Likewise, in the same space, a minimal ground state energy E_g was also obtained. For d-wave channel both minima are localized around the same optimal doping, however, for s* symmetry, the two minima are located at different electron concentrations. In this work, we additionally study how the p-wave ground-state energy and the critical temperature depend on the hoppings parameters and the electron concentration. The results show that for p-wave, minimum global values of  and  in the space do exist too, they are found around half filling but, as occurs for s*- wave, the minimum of T_(c-max) does not occur at the same point as . Moreover, we present a ground-state phase diagram in the space (t’)⁄(t,n_op) where it is possible to find zones of coexistence and competition between the s*-, p- and d-wave symmetries. Also, an analysis of the shape of the Fermi surface and the single-particle energy, as functions of the wave vector of an electron in the Cooper pair, has been done for different regions of the mentioned space.

scholarly journals The Structure of Amyloid Versus the Structure of Globular Proteins

2020 ◽  
Vol 21 (13) ◽  
pp. 4683 ◽  
Author(s):  
Piotr Fabian ◽  
Mateusz Banach ◽  
Katarzyna Stapor ◽  
Leszek Konieczny ◽  
Magdalena Ptak-Kaczor ◽  
...  
Keyword(s):  
Gaussian Distribution ◽  
Experimental Studies ◽  
Data Bank ◽  
Globular Proteins ◽  
Hydrophobic Core ◽  
Single Chain ◽  
Spherical Micelle ◽  
Globular Structure ◽  
A Chain ◽  
High Level

The issue of changing the structure of globular proteins into an amyloid form is in the focus of researchers' attention. Numerous experimental studies are carried out, and mathematical models to define the essence of amyloid transformation are sought. The present work focuses on the issue of the hydrophobic core structure in amyloids. The form of ordering the hydrophobic core in globular proteins is described by a 3D Gaussian distribution analog to the distribution of hydrophobicity in a spherical micelle. Amyloid fibril is a ribbon-like micelle made up of numerous individual chains, each representing a flat structure. The distribution of hydrophobicity within a single chain included in the fibril describes the 2D Gaussian distribution. Such a description expresses the location of polar residues on a circle with a center with a high level of hydrophobicity. The presence of this type of order in the amyloid forms available in Preotin Data Bank (PDB) (both in proto- and superfibrils) is demonstrated in the present work. In this system, it can be assumed that the amyloid transformation is a chain transition from 3D Gauss ordering to 2D Gauss ordering. This means changing the globular structure to a ribbon-like structure. This observation can provide a simple mathematical model for simulating the amyloid transformation of proteins.

scholarly journals Adsorption and Corrosion Performance of New Cationic Gemini Surfactants Derivatives of Fatty Amido Ethyl Aminium Chloride with Ester Spacer for Mild Steel in Acidic Solutions

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2790
Author(s):  
Nashwa S. Bin-Hudayb ◽  
Entsar E. Badr ◽  
M.A. Hegazy
Keyword(s):  
Mild Steel ◽  
Gemini Surfactants ◽  
Ester Group ◽  
Charge Transfer Resistance ◽  
Maximum Efficiency ◽  
Transfer Resistance ◽  
Cationic Gemini Surfactants ◽  
Hydrophobic Chain ◽  
Inhibition Performance ◽  
Chain Lengths

Three new cationic gemini surfactants with ester spacer type 2-2′-(ethane-1,2-diyl bis(oxy)) bis(N-(2-alkanamidoethyl)-N,N-dimethyl-2-oxoethan-1-aminium)) dichloride) (CGSES12, CGSES14 and CGSES16), based on N,N-dimethyl fatty amido ethylamine, were produced. These gemini quaternary ammonium salts were synthesized using a three-step reaction method, starting from th/e condensation of the fatty acid chloride (RCOCl) of various hydrophobic chain lengths (R, C11H23, C13H27, C15H31) with N,N-dimethyl ethylene diamine, followed by the quaternization of the tertiary amino group formed with the spacer of the ester group formed in the second step. The chemical configuration of the surfactants was established by FT-IR, 1HNMR, 13CNMR and Mass spectroscopies. The inhibition performance of three surfactants was studied by weight loss and electrochemical measurements. The results show that CGSES12, CGSES14 and CGSES16 behave as effective inhibitors and surface agents. The maximum efficiency was higher than 94% at 2.5 mM, and the inhibition order was CGSES16 > CGSES14 > CGSES12. This was due to the increment in hydrophobicity of the gemini surfactants. Their adsorption on a mild steel surface followed the Langmuir isotherm. CGSES12, CGSES14 and CGSES16 can be considered mixed-type inhibitors. The presence of CGSES12, CGSES14 and CGSES16 increased charge transfer resistance and decreased the corrosion rate. The adsorption focused on heteroatoms and the surface properties of cationic gemini surfactants.

scholarly journals Complete catalog of ground-state diagrams for the general three-state lattice-gas model with nearest-neighbor interactions on a square lattice

2019 ◽  
Vol 21 (11) ◽  
pp. 6216-6223 ◽  
Author(s):  
Daniel Silva ◽  
Per Arne Rikvold
Keyword(s):  
Phase Diagrams ◽  
Ground State ◽  
Lattice Gas ◽  
Nearest Neighbor ◽  
Square Lattice ◽  
Temperature Phase ◽  
Zero Temperature ◽  
Dimensional Parameter ◽  
State Diagrams ◽  
Solid Foundation

The fifteen topologically different zero-temperature phase diagrams in the model's full, five-dimensional parameter space provide a solid foundation for studies at finite temperatures.

scholarly journals Entanglement Transfer through an Antiferromagnetic Spin Chain

2010 ◽  
Vol 2010 ◽  
pp. 1-11 ◽  
Author(s):  
Abolfazl Bayat ◽  
Sougato Bose
Keyword(s):  
Ground State ◽  
Spin Chain ◽  
The Other ◽  
Heisenberg Chain ◽  
Ferromagnetic Chain ◽  
Pulse Form ◽  
Entanglement Transfer ◽  
A Chain ◽  
Antiferromagnetic Spin

We study the possibility of using an uniformly coupled finite antiferromagnetic spin-1/2 Heisenberg chain as a channel for transmitting entanglement. One member of a pair of maximally entangled spins is initially appended to one end of a chain in its ground state and the dynamical propagation of this entanglement to the other end is calculated. We show that, compared to the analogous scheme with a ferromagnetic chain in its ground state, here the entanglement is transmitted faster, with less decay, with a much higher purity and as a narrow pulse form rising nonanalytically from zero. Here nonzero temperatures and depolarizing environments are both found to be less destructive in comparison to the ferromagnetic case. The entanglement is found to propagate through the chain in a peculiar fashion whereby it hops to skip alternate sites.

GROUND STATE OF THE 2D EXTENDED HUBBARD MODEL WITH MORE THAN NEAREST-NEIGHBOR INTERACTIONS

2012 ◽  
Vol 26 (29) ◽  
pp. 1250156 ◽  
Author(s):  
S. HARIR ◽  
M. BENNAI ◽  
Y. BOUGHALEB
Keyword(s):  
Phase Diagram ◽  
Hubbard Model ◽  
Ground State ◽  
State Energy ◽  
Nearest Neighbor ◽  
Finite Size ◽  
Square Lattice ◽  
Extended Hubbard Model ◽  
Eigenvalues And Eigenvectors ◽  
Repulsion Energy

We investigate the ground state phase diagram of the two dimensional Extended Hubbard Model (EHM) with more than Nearest-Neighbor (NN) interactions for finite size system at low concentration. This EHM is solved analytically for finite square lattice at one-eighth filling. All eigenvalues and eigenvectors are given as a function of the on-site repulsion energy U and the off-site interaction energy Vij. The behavior of the ground state energy exhibits the emergence of phase diagram. The obtained results clearly underline that interactions exceeding NN distances in range can significantly influence the emergence of the ground state conductor–insulator transition.

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